From 994fd783e4e977d6faf7f8f56fa6a730896b36d4 Mon Sep 17 00:00:00 2001
From: Josh Goldberg <git@joshuakgoldberg.com>
Date: Tue, 14 Jan 2025 11:07:47 -0500
Subject: [PATCH 1/5] feat: split file system into create-fs, with
 diffCreatedDirectory tester

---
 packages/create-fs/README.md                  |  17 ++
 packages/create-fs/package.json               |  39 ++++
 .../create-fs/src/createReadingFileSystem.ts  |  11 +
 .../create-fs/src/createWritingFileSystem.ts  |  14 ++
 packages/create-fs/src/index.ts               |   5 +
 .../src/intake/intakeFromDirectory.ts         |  31 +++
 packages/create-fs/src/types/files.ts         |  21 ++
 packages/create-fs/src/types/system.ts        |  30 +++
 packages/create-fs/tsconfig.json              |   8 +
 packages/create-fs/vitest.config.ts           |   8 +
 packages/create-testers/package.json          |   8 +-
 .../create-testers/src/createMockSystems.ts   |   4 +-
 .../src/diffCreatedDirectory.ts               | 198 ++++++++++++++++++
 packages/create-testers/src/index.ts          |   1 +
 packages/create-testers/src/types.ts          |   3 +-
 packages/create/package.json                  |   4 +-
 .../cli/prompts/promptForBaseOptions.test.ts  |   1 +
 .../create/src/creators/createInput.test.ts   |  10 +-
 packages/create/src/index.ts                  |   1 -
 ...est.ts => mergeCreatedDirectories.test.ts} |  20 +-
 ...reations.ts => mergeCreatedDirectories.ts} |  25 ++-
 packages/create/src/mergers/mergeCreations.ts |   4 +-
 .../src/mergers/mergeFileEntries.test.ts      |   2 +-
 .../create/src/mergers/mergeFileEntries.ts    |   2 +-
 .../create/src/producers/produceBase.test.ts  |   1 +
 .../src/producers/produceBlocks.test.ts       |   7 +-
 .../src/producers/producePreset.test.ts       |   1 +
 .../create/src/runners/applyFilesToSystem.ts  |   8 +-
 packages/create/src/runners/runBlock.test.ts  |   1 +
 packages/create/src/runners/runPreset.test.ts |   1 +
 .../create/src/system/createSystemContext.ts  |   3 +-
 .../src/system/createWritingFileSystem.ts     |  13 --
 packages/create/src/types/creations.ts        |  24 +--
 packages/create/src/types/inputs.ts           |  10 +-
 packages/create/src/types/system.ts           |  19 +-
 packages/site/astro.config.ts                 |  11 +-
 .../docs/engine/packages/create-fs.mdx        |  40 ++++
 .../create-testers.mdx}                       |  12 +-
 pnpm-lock.yaml                                |  54 ++++-
 tsconfig.build.json                           |   1 +
 40 files changed, 571 insertions(+), 102 deletions(-)
 create mode 100644 packages/create-fs/README.md
 create mode 100644 packages/create-fs/package.json
 create mode 100644 packages/create-fs/src/createReadingFileSystem.ts
 create mode 100644 packages/create-fs/src/createWritingFileSystem.ts
 create mode 100644 packages/create-fs/src/index.ts
 create mode 100644 packages/create-fs/src/intake/intakeFromDirectory.ts
 create mode 100644 packages/create-fs/src/types/files.ts
 create mode 100644 packages/create-fs/src/types/system.ts
 create mode 100644 packages/create-fs/tsconfig.json
 create mode 100644 packages/create-fs/vitest.config.ts
 create mode 100644 packages/create-testers/src/diffCreatedDirectory.ts
 rename packages/create/src/mergers/{mergeFileCreations.test.ts => mergeCreatedDirectories.test.ts} (68%)
 rename packages/create/src/mergers/{mergeFileCreations.ts => mergeCreatedDirectories.ts} (60%)
 delete mode 100644 packages/create/src/system/createWritingFileSystem.ts
 create mode 100644 packages/site/src/content/docs/engine/packages/create-fs.mdx
 rename packages/site/src/content/docs/engine/{apis/testers.mdx => packages/create-testers.mdx} (98%)

diff --git a/packages/create-fs/README.md b/packages/create-fs/README.md
new file mode 100644
index 00000000..b2435a92
--- /dev/null
+++ b/packages/create-fs/README.md
@@ -0,0 +1,17 @@
+<h1 align="center">create-fs</h1>
+
+<p align="center">The file system used by <a href="https://create.bingo"><code>create</code></a>. 🗄️</p>
+
+<p align="center">
+	<a href="https://github.com/JoshuaKGoldberg/create/blob/main/.github/CODE_OF_CONDUCT.md" target="_blank"><img alt="🤝 Code of Conduct: Kept" src="https://img.shields.io/badge/%F0%9F%A4%9D_code_of_conduct-kept-21bb42" /></a>
+	<a href="https://codecov.io/gh/JoshuaKGoldberg/create" target="_blank"><img alt="🧪 Coverage" src="https://img.shields.io/codecov/c/github/JoshuaKGoldberg/create?label=%F0%9F%A7%AA%20coverage" /></a>
+	<a href="https://github.com/JoshuaKGoldberg/create/blob/main/LICENSE.md" target="_blank"><img alt="📝 License: MIT" src="https://img.shields.io/badge/%F0%9F%93%9D_license-MIT-21bb42.svg"></a>
+	<a href="http://npmjs.com/package/create-testers"><img alt="📦 npm version" src="https://img.shields.io/npm/v/create-testers?color=21bb42&label=%F0%9F%93%A6%20npm" /></a>
+	<img alt="💪 TypeScript: Strict" src="https://img.shields.io/badge/%F0%9F%92%AA_typescript-strict-21bb42.svg" />
+</p>
+
+See **[create.bingo](https://create.bingo)** for documentation.
+Specifically:
+
+- [Packages > `create-fs`](https://www.create.bingo/engine/packages/create-fs): for this package's documentation
+- [Runtime > Creations > `files`](https://www.create.bingo/engine/runtime/creations#files): for where these are used
diff --git a/packages/create-fs/package.json b/packages/create-fs/package.json
new file mode 100644
index 00000000..2f35edf9
--- /dev/null
+++ b/packages/create-fs/package.json
@@ -0,0 +1,39 @@
+{
+	"name": "create-fs",
+	"version": "0.1.0",
+	"description": "The file system used by create>. 🗄️",
+	"repository": {
+		"type": "git",
+		"url": "https://github.com/JoshuaKGoldberg/create",
+		"directory": "packages/create-fs"
+	},
+	"license": "MIT",
+	"author": {
+		"name": "Josh Goldberg ✨",
+		"email": "npm@joshuakgoldberg.com"
+	},
+	"type": "module",
+	"main": "./lib/index.js",
+	"files": [
+		"lib/",
+		"package.json",
+		"LICENSE.md",
+		"README.md"
+	],
+	"scripts": {
+		"build": "tsc"
+	},
+	"dependencies": {
+		"octokit": "^4.0.2"
+	},
+	"devDependencies": {
+		"@types/node": "^22.10.5",
+		"zod": "3.24.1"
+	},
+	"peerDependencies": {
+		"create": "workspace:^"
+	},
+	"engines": {
+		"node": ">=18"
+	}
+}
diff --git a/packages/create-fs/src/createReadingFileSystem.ts b/packages/create-fs/src/createReadingFileSystem.ts
new file mode 100644
index 00000000..acfb824c
--- /dev/null
+++ b/packages/create-fs/src/createReadingFileSystem.ts
@@ -0,0 +1,11 @@
+import * as fs from "node:fs/promises";
+
+import { ReadingFileSystem } from "./types/system.js";
+
+export function createReadingFileSystem(): ReadingFileSystem {
+	return {
+		readDirectory: async (filePath: string) => await fs.readdir(filePath),
+		readFile: async (filePath: string) =>
+			(await fs.readFile(filePath)).toString(),
+	};
+}
diff --git a/packages/create-fs/src/createWritingFileSystem.ts b/packages/create-fs/src/createWritingFileSystem.ts
new file mode 100644
index 00000000..72a6efa0
--- /dev/null
+++ b/packages/create-fs/src/createWritingFileSystem.ts
@@ -0,0 +1,14 @@
+import * as fs from "node:fs/promises";
+
+import { createReadingFileSystem } from "./createReadingFileSystem.js";
+
+export function createWritingFileSystem() {
+	return {
+		...createReadingFileSystem(),
+		writeDirectory: async (directoryPath: string) =>
+			void (await fs.mkdir(directoryPath, { recursive: true })),
+		writeFile: async (filePath: string, contents: string) => {
+			await fs.writeFile(filePath, contents);
+		},
+	};
+}
diff --git a/packages/create-fs/src/index.ts b/packages/create-fs/src/index.ts
new file mode 100644
index 00000000..f7c8e225
--- /dev/null
+++ b/packages/create-fs/src/index.ts
@@ -0,0 +1,5 @@
+export * from "./createReadingFileSystem.js";
+export * from "./createWritingFileSystem.js";
+export * from "./intake/intakeFromDirectory.js";
+export type * from "./types/files.js";
+export type * from "./types/system.js";
diff --git a/packages/create-fs/src/intake/intakeFromDirectory.ts b/packages/create-fs/src/intake/intakeFromDirectory.ts
new file mode 100644
index 00000000..724dfe53
--- /dev/null
+++ b/packages/create-fs/src/intake/intakeFromDirectory.ts
@@ -0,0 +1,31 @@
+import * as fs from "node:fs/promises";
+import path from "node:path";
+
+import { CreatedDirectory } from "../types/files.js";
+
+export interface IntakeFromDirectorySettings {
+	exclude: RegExp;
+}
+
+export async function intakeFromDirectory(
+	directoryPath: string,
+	settings: IntakeFromDirectorySettings,
+) {
+	const files: CreatedDirectory = {};
+	const children = await fs.readdir(directoryPath);
+
+	for (const child of children) {
+		if (settings.exclude.test(child)) {
+			continue;
+		}
+
+		const childPath = path.join(directoryPath, child);
+		const stat = await fs.stat(childPath);
+
+		files[child] = stat.isDirectory()
+			? await intakeFromDirectory(childPath, settings)
+			: [(await fs.readFile(childPath)).toString(), { mode: stat.mode }];
+	}
+
+	return files;
+}
diff --git a/packages/create-fs/src/types/files.ts b/packages/create-fs/src/types/files.ts
new file mode 100644
index 00000000..ad193841
--- /dev/null
+++ b/packages/create-fs/src/types/files.ts
@@ -0,0 +1,21 @@
+// eslint-disable-next-line @eslint-community/eslint-comments/disable-enable-pair
+/* eslint-disable @typescript-eslint/consistent-indexed-object-style */
+
+export interface CreatedDirectory {
+	[i: string]: CreatedFileEntry | undefined;
+}
+
+export type CreatedFileEntry =
+	| [string, CreatedFileOptions]
+	| [string]
+	| CreatedDirectory
+	| false
+	| string;
+
+export interface CreatedFileOptions {
+	/**
+	 * File mode (permission and sticky bits) per chmod().
+	 * @example 0o777 for an executable file.
+	 */
+	mode?: number;
+}
diff --git a/packages/create-fs/src/types/system.ts b/packages/create-fs/src/types/system.ts
new file mode 100644
index 00000000..578b3687
--- /dev/null
+++ b/packages/create-fs/src/types/system.ts
@@ -0,0 +1,30 @@
+export interface DirectoryChild {
+	name: string;
+	type: "directory" | "file";
+}
+
+export type ReadDirectory = (filePath: string) => Promise<string[]>;
+
+export type ReadFile = (filePath: string) => Promise<string>;
+
+export interface ReadingFileSystem {
+	readDirectory: ReadDirectory;
+	readFile: ReadFile;
+}
+
+export type WriteDirectory = (directoryPath: string) => Promise<void>;
+
+export type WriteFile = (
+	filePath: string,
+	contents: string,
+	options?: WriteFileOptions,
+) => Promise<void>;
+
+export interface WriteFileOptions {
+	mode?: number;
+}
+
+export interface WritingFileSystem extends ReadingFileSystem {
+	writeDirectory: WriteDirectory;
+	writeFile: WriteFile;
+}
diff --git a/packages/create-fs/tsconfig.json b/packages/create-fs/tsconfig.json
new file mode 100644
index 00000000..de061cbc
--- /dev/null
+++ b/packages/create-fs/tsconfig.json
@@ -0,0 +1,8 @@
+{
+	"compilerOptions": {
+		"outDir": "lib",
+		"rootDir": "src"
+	},
+	"extends": "../../tsconfig.base.json",
+	"include": ["src"]
+}
diff --git a/packages/create-fs/vitest.config.ts b/packages/create-fs/vitest.config.ts
new file mode 100644
index 00000000..5966133b
--- /dev/null
+++ b/packages/create-fs/vitest.config.ts
@@ -0,0 +1,8 @@
+import { defineProject } from "vitest/config";
+
+export default defineProject({
+	test: {
+		clearMocks: true,
+		exclude: ["lib", "node_modules"],
+	},
+});
diff --git a/packages/create-testers/package.json b/packages/create-testers/package.json
index 1f65f5da..81b65035 100644
--- a/packages/create-testers/package.json
+++ b/packages/create-testers/package.json
@@ -24,13 +24,17 @@
 		"build": "tsc"
 	},
 	"dependencies": {
-		"octokit": "^4.0.2"
+		"diff": "^7.0.0",
+		"octokit": "^4.0.2",
+		"without-undefined-properties": "^0.1.1"
 	},
 	"devDependencies": {
+		"@types/diff": "^7.0.0",
 		"zod": "3.24.1"
 	},
 	"peerDependencies": {
-		"create": "workspace:^"
+		"create": "workspace:^",
+		"create-fs": "workspace:^"
 	},
 	"engines": {
 		"node": ">=18"
diff --git a/packages/create-testers/src/createMockSystems.ts b/packages/create-testers/src/createMockSystems.ts
index 38d41018..16a265bd 100644
--- a/packages/create-testers/src/createMockSystems.ts
+++ b/packages/create-testers/src/createMockSystems.ts
@@ -1,4 +1,5 @@
-import { NativeSystem, TakeInput, WritingFileSystem } from "create";
+import { NativeSystem, TakeInput } from "create";
+import { WritingFileSystem } from "create-fs";
 import { Octokit } from "octokit";
 
 import { MockSystemOptions } from "./types.js";
@@ -20,6 +21,7 @@ export function createMockSystems(
 	};
 
 	const fs: WritingFileSystem = {
+		readDirectory: createFailingFunction("fs.readDirectory", "an input"),
 		readFile: createFailingFunction("fs.readFile", "an input"),
 		writeDirectory: createFailingFunction("fs.writeDirectory", "an input"),
 		writeFile: createFailingFunction("fs.writeFile", "an input"),
diff --git a/packages/create-testers/src/diffCreatedDirectory.ts b/packages/create-testers/src/diffCreatedDirectory.ts
new file mode 100644
index 00000000..e8e0f13b
--- /dev/null
+++ b/packages/create-testers/src/diffCreatedDirectory.ts
@@ -0,0 +1,198 @@
+import {
+	CreatedDirectory,
+	CreatedFileEntry,
+	CreatedFileOptions,
+} from "create-fs";
+import { createTwoFilesPatch } from "diff";
+import path from "node:path";
+import { withoutUndefinedProperties } from "without-undefined-properties";
+
+export interface DiffedCreatedDirectory {
+	[i: string]: DiffedCreatedDirectory | DiffedCreatedFileEntry | undefined;
+}
+
+export type DiffedCreatedFileEntry =
+	| [string, DiffedCreatedFileOptions]
+	| [string]
+	| CreatedFileEntry
+	| DiffedCreatedDirectory
+	| string;
+
+export interface DiffedCreatedFileOptions {
+	mode?: string;
+}
+
+export type ProcessText = (text: string, filePath: string) => string;
+
+export function diffCreatedDirectory(
+	actual: CreatedDirectory,
+	created: CreatedDirectory,
+	processText: ProcessText,
+): DiffedCreatedDirectory | undefined {
+	const result = diffCreatedDirectoryWorker(actual, created, ".", processText);
+
+	return result && withoutUndefinedProperties(result);
+}
+
+export function diffCreatedDirectoryWorker(
+	actual: CreatedDirectory,
+	created: CreatedDirectory,
+	pathTo: string,
+	processText: ProcessText,
+): DiffedCreatedDirectory | undefined {
+	const result: DiffedCreatedDirectory = {};
+
+	for (const [childName, childCreated] of Object.entries(created)) {
+		if (!(childName in actual)) {
+			result[childName] = childCreated;
+			continue;
+		}
+
+		const childActual = actual[childName];
+		const pathToChild = path.join(pathTo, childName);
+
+		const childDiffed = diffCreatedDirectoryChild(
+			childActual,
+			childCreated,
+			pathToChild,
+			processText,
+		);
+
+		if (childDiffed !== undefined) {
+			result[childName] = childDiffed;
+		}
+	}
+
+	const trimmed = withoutUndefinedProperties(result);
+
+	return Object.keys(trimmed).length === 0 ? undefined : result;
+}
+
+function diffCreatedDirectoryChild(
+	childActual: CreatedFileEntry | undefined,
+	childCreated: CreatedFileEntry | undefined,
+	pathToChild: string,
+	processText: ProcessText,
+): DiffedCreatedFileEntry | undefined {
+	if (childActual === undefined) {
+		return childCreated;
+	}
+
+	if (childCreated === undefined) {
+		return undefined;
+	}
+
+	if (typeof childActual === "string") {
+		if (typeof childCreated === "string") {
+			return diffCreatedFileText(
+				childActual,
+				childCreated,
+				pathToChild,
+				processText,
+			);
+		}
+	}
+
+	if (Array.isArray(childActual)) {
+		if (Array.isArray(childCreated)) {
+			const fileDiff = diffCreatedFileText(
+				childActual[0],
+				childCreated[0],
+				pathToChild,
+				processText,
+			);
+			const optionsDiff = diffCreatedFileOptions(
+				childActual[1],
+				childCreated[1],
+				pathToChild,
+			);
+			return fileDiff || optionsDiff
+				? [fileDiff ?? "", optionsDiff ?? {}]
+				: undefined;
+		}
+
+		if (typeof childCreated === "string") {
+			return diffCreatedFileText(
+				childActual[0],
+				childCreated,
+				pathToChild,
+				processText,
+			);
+		}
+
+		return `Mismatched ${pathToChild}: actual is a created file; created is ${typeof childCreated}.`;
+	}
+
+	if (Array.isArray(childCreated)) {
+		if (typeof childActual === "string") {
+			return diffCreatedFileText(
+				childActual,
+				childCreated[0],
+				pathToChild,
+				processText,
+			);
+		}
+
+		return `Mismatched ${pathToChild}: actual is ${typeof childActual}; created is a created file.`;
+	}
+
+	if (typeof childActual === "object") {
+		if (typeof childCreated === "object") {
+			return diffCreatedDirectoryWorker(
+				childActual,
+				childCreated,
+				pathToChild,
+				processText,
+			);
+		}
+	}
+
+	return `Mismatched ${pathToChild}: actual is ${typeof childActual}; created is ${typeof childCreated}.`;
+}
+
+function diffCreatedFileText(
+	actual: string,
+	created: string,
+	pathToFile: string,
+	processText: ProcessText,
+) {
+	const actualProcessed = processText(created, pathToFile);
+	const createdProcessed = processText(actual, pathToFile);
+
+	return actualProcessed === createdProcessed
+		? undefined
+		: createTwoFilesPatch(
+				pathToFile,
+				pathToFile,
+				actualProcessed,
+				createdProcessed,
+			).replace(/^Index: .+\n=+\n-{3} .+\n\+{3} .+\n/gmu, "");
+}
+
+/**
+ * @todo
+ * Unclear yet how to represent a diff in the mode...
+ * Should a DiffedFileEntry type replace CreatedFileOptions.mode with string?
+ */
+function diffCreatedFileOptions(
+	actual: CreatedFileOptions | undefined,
+	created: CreatedFileOptions | undefined,
+	pathToFile: string,
+): DiffedCreatedFileOptions | undefined {
+	if (
+		actual?.mode === undefined ||
+		created?.mode === undefined ||
+		actual.mode === created.mode
+	) {
+		return undefined;
+	}
+
+	return {
+		mode: diffCreatedFileText(
+			actual.mode.toString(16),
+			created.mode.toString(16),
+			pathToFile,
+			(text) => text,
+		),
+	};
+}
diff --git a/packages/create-testers/src/index.ts b/packages/create-testers/src/index.ts
index 297b2e02..c1838ff4 100644
--- a/packages/create-testers/src/index.ts
+++ b/packages/create-testers/src/index.ts
@@ -1,3 +1,4 @@
+export { diffCreatedDirectory } from "./diffCreatedDirectory.js";
 export { testBase } from "./testBase.js";
 export { testBlock } from "./testBlock.js";
 export { testInput } from "./testInput.js";
diff --git a/packages/create-testers/src/types.ts b/packages/create-testers/src/types.ts
index c2af93cb..42ba020d 100644
--- a/packages/create-testers/src/types.ts
+++ b/packages/create-testers/src/types.ts
@@ -1,4 +1,5 @@
-import { SystemRunner, TakeInput, WritingFileSystem } from "create";
+import { SystemRunner, TakeInput } from "create";
+import { WritingFileSystem } from "create-fs";
 
 export interface MockSystemOptions {
 	fetch?: typeof fetch;
diff --git a/packages/create/package.json b/packages/create/package.json
index 8abbf069..a2915168 100644
--- a/packages/create/package.json
+++ b/packages/create/package.json
@@ -28,6 +28,7 @@
 		"@clack/prompts": "^0.9.0",
 		"cached-factory": "^0.1.0",
 		"chalk": "^5.4.0",
+		"create-fs": "workspace:^",
 		"execa": "^9.5.2",
 		"get-github-auth-token": "^0.1.0",
 		"hash-object": "^5.0.1",
@@ -40,7 +41,8 @@
 		"zod": "^3.24.1"
 	},
 	"devDependencies": {
-		"@types/hosted-git-info": "3.0.5"
+		"@types/hosted-git-info": "3.0.5",
+		"@types/node": "^22.10.5"
 	},
 	"engines": {
 		"node": ">=18"
diff --git a/packages/create/src/cli/prompts/promptForBaseOptions.test.ts b/packages/create/src/cli/prompts/promptForBaseOptions.test.ts
index 697fe463..0bef89c3 100644
--- a/packages/create/src/cli/prompts/promptForBaseOptions.test.ts
+++ b/packages/create/src/cli/prompts/promptForBaseOptions.test.ts
@@ -27,6 +27,7 @@ const system = {
 		octokit: {} as Octokit,
 	},
 	fs: {
+		readDirectory: vi.fn(),
 		readFile: vi.fn(),
 		writeDirectory: vi.fn(),
 		writeFile: vi.fn(),
diff --git a/packages/create/src/creators/createInput.test.ts b/packages/create/src/creators/createInput.test.ts
index 23c986fb..854e5931 100644
--- a/packages/create/src/creators/createInput.test.ts
+++ b/packages/create/src/creators/createInput.test.ts
@@ -14,7 +14,10 @@ describe("createInput", () => {
 
 		const actual = input({
 			fetchers: createSystemFetchers({ fetch: vi.fn() }),
-			fs: { readFile: vi.fn() },
+			fs: {
+				readDirectory: vi.fn(),
+				readFile: vi.fn(),
+			},
 			runner: vi.fn(),
 			take: vi.fn(),
 		});
@@ -37,7 +40,10 @@ describe("createInput", () => {
 				offset: 1000,
 			},
 			fetchers: createSystemFetchers({ fetch: vi.fn() }),
-			fs: { readFile: vi.fn() },
+			fs: {
+				readDirectory: vi.fn(),
+				readFile: vi.fn(),
+			},
 			runner: vi.fn(),
 			take: vi.fn(),
 		});
diff --git a/packages/create/src/index.ts b/packages/create/src/index.ts
index 35076a9e..d6db9e6b 100644
--- a/packages/create/src/index.ts
+++ b/packages/create/src/index.ts
@@ -23,7 +23,6 @@ export * from "./runners/runPreset.js";
 // TODO: These might be better as their own packages?
 export * from "./runners/applyFilesToSystem.js";
 export * from "./system/createSystemContext.js";
-export * from "./system/createWritingFileSystem.js";
 export * from "./utils/awaitLazyProperties.js";
 
 // Types
diff --git a/packages/create/src/mergers/mergeFileCreations.test.ts b/packages/create/src/mergers/mergeCreatedDirectories.test.ts
similarity index 68%
rename from packages/create/src/mergers/mergeFileCreations.test.ts
rename to packages/create/src/mergers/mergeCreatedDirectories.test.ts
index c73ee7b3..87c59fac 100644
--- a/packages/create/src/mergers/mergeFileCreations.test.ts
+++ b/packages/create/src/mergers/mergeCreatedDirectories.test.ts
@@ -1,7 +1,7 @@
+import { CreatedDirectory } from "create-fs";
 import { describe, expect, test } from "vitest";
 
-import { CreatedFiles } from "../types/creations.js";
-import { mergeFileCreations } from "./mergeFileCreations.js";
+import { mergeCreatedDirectories } from "./mergeCreatedDirectories.js";
 
 describe("mergeFileCreations", () => {
 	test.each([
@@ -27,13 +27,21 @@ describe("mergeFileCreations", () => {
 			{ a: "" },
 			"Conflicting created directory and file at path: 'a'.",
 		],
-	] satisfies [CreatedFiles, CreatedFiles, CreatedFiles | string][])(
+	] satisfies [
+		CreatedDirectory,
+		CreatedDirectory,
+		CreatedDirectory | string,
+	][])(
 		"%j with %j",
-		(first: CreatedFiles, second: CreatedFiles, expected?: object | string) => {
+		(
+			first: CreatedDirectory,
+			second: CreatedDirectory,
+			expected?: object | string,
+		) => {
 			if (typeof expected === "string") {
-				expect(() => mergeFileCreations(first, second)).toThrow(expected);
+				expect(() => mergeCreatedDirectories(first, second)).toThrow(expected);
 			} else {
-				expect(mergeFileCreations(first, second)).toEqual(expected);
+				expect(mergeCreatedDirectories(first, second)).toEqual(expected);
 			}
 		},
 	);
diff --git a/packages/create/src/mergers/mergeFileCreations.ts b/packages/create/src/mergers/mergeCreatedDirectories.ts
similarity index 60%
rename from packages/create/src/mergers/mergeFileCreations.ts
rename to packages/create/src/mergers/mergeCreatedDirectories.ts
index af8d7cdb..f5583a86 100644
--- a/packages/create/src/mergers/mergeFileCreations.ts
+++ b/packages/create/src/mergers/mergeCreatedDirectories.ts
@@ -1,19 +1,20 @@
-import { CreatedFiles } from "../types/creations.js";
+import { CreatedDirectory } from "create-fs";
+
 import { mergeFileEntries } from "./mergeFileEntries.js";
 
-export function mergeFileCreations(
-	firsts: CreatedFiles,
-	seconds: CreatedFiles,
+export function mergeCreatedDirectories(
+	firsts: CreatedDirectory,
+	seconds: CreatedDirectory,
 ) {
-	return mergeFileCreationsWorker(firsts, seconds, []);
+	return mergeCreatedDirectoriesWorker(firsts, seconds, []);
 }
 
-function mergeFileCreationsWorker(
-	firsts: CreatedFiles,
-	seconds: CreatedFiles,
+function mergeCreatedDirectoriesWorker(
+	firsts: CreatedDirectory,
+	seconds: CreatedDirectory,
 	path: string[],
 ) {
-	const result: CreatedFiles = { ...firsts };
+	const result: CreatedDirectory = { ...firsts };
 
 	for (const i in seconds) {
 		const second = seconds[i];
@@ -36,7 +37,11 @@ function mergeFileCreationsWorker(
 		}
 
 		result[i] = firstIsDirectory
-			? mergeFileCreationsWorker(first, second as CreatedFiles, nextPath)
+			? mergeCreatedDirectoriesWorker(
+					first,
+					second as CreatedDirectory,
+					nextPath,
+				)
 			: mergeFileEntries(first, second, nextPath);
 	}
 
diff --git a/packages/create/src/mergers/mergeCreations.ts b/packages/create/src/mergers/mergeCreations.ts
index b326f690..e16097ce 100644
--- a/packages/create/src/mergers/mergeCreations.ts
+++ b/packages/create/src/mergers/mergeCreations.ts
@@ -3,7 +3,7 @@ import { withoutUndefinedProperties } from "without-undefined-properties";
 import { Creation } from "../types/creations.js";
 import { applyMerger } from "./applyMerger.js";
 import { mergeAddons } from "./mergeAddons.js";
-import { mergeFileCreations } from "./mergeFileCreations.js";
+import { mergeCreatedDirectories } from "./mergeCreatedDirectories.js";
 import { mergeRequests } from "./mergeRequests.js";
 import { mergeScripts } from "./mergeScripts.js";
 import { mergeSuggestions } from "./mergeSuggestions.js";
@@ -14,7 +14,7 @@ export function mergeCreations<Options extends object>(
 ): Partial<Creation<Options>> {
 	return withoutUndefinedProperties({
 		addons: applyMerger(first.addons, second.addons, mergeAddons),
-		files: applyMerger(first.files, second.files, mergeFileCreations),
+		files: applyMerger(first.files, second.files, mergeCreatedDirectories),
 		requests: applyMerger(first.requests, second.requests, mergeRequests),
 		scripts: applyMerger(first.scripts, second.scripts, mergeScripts),
 		suggestions: applyMerger(
diff --git a/packages/create/src/mergers/mergeFileEntries.test.ts b/packages/create/src/mergers/mergeFileEntries.test.ts
index 047297ab..2bda5c65 100644
--- a/packages/create/src/mergers/mergeFileEntries.test.ts
+++ b/packages/create/src/mergers/mergeFileEntries.test.ts
@@ -1,6 +1,6 @@
+import { CreatedFileEntry } from "create-fs";
 import { describe, expect, test } from "vitest";
 
-import { CreatedFileEntry } from "../types/creations.js";
 import { mergeFileEntries } from "./mergeFileEntries.js";
 
 const path = ["test", "path"];
diff --git a/packages/create/src/mergers/mergeFileEntries.ts b/packages/create/src/mergers/mergeFileEntries.ts
index dad2d8cc..3336ea38 100644
--- a/packages/create/src/mergers/mergeFileEntries.ts
+++ b/packages/create/src/mergers/mergeFileEntries.ts
@@ -1,4 +1,4 @@
-import { CreatedFileEntry } from "../types/creations.js";
+import { CreatedFileEntry } from "create-fs";
 
 export function mergeFileEntries(
 	first: CreatedFileEntry | undefined,
diff --git a/packages/create/src/producers/produceBase.test.ts b/packages/create/src/producers/produceBase.test.ts
index 1937adf1..572c29f1 100644
--- a/packages/create/src/producers/produceBase.test.ts
+++ b/packages/create/src/producers/produceBase.test.ts
@@ -11,6 +11,7 @@ const system = {
 		octokit: {} as Octokit,
 	},
 	fs: {
+		readDirectory: vi.fn(),
 		readFile: vi.fn(),
 		writeDirectory: vi.fn(),
 		writeFile: vi.fn(),
diff --git a/packages/create/src/producers/produceBlocks.test.ts b/packages/create/src/producers/produceBlocks.test.ts
index 67e93981..2b1485ea 100644
--- a/packages/create/src/producers/produceBlocks.test.ts
+++ b/packages/create/src/producers/produceBlocks.test.ts
@@ -12,7 +12,12 @@ const presetContext = {
 		log: vi.fn(),
 	},
 	fetchers: createSystemFetchers({ fetch: vi.fn() }),
-	fs: { readFile: vi.fn(), writeDirectory: vi.fn(), writeFile: vi.fn() },
+	fs: {
+		readDirectory: vi.fn(),
+		readFile: vi.fn(),
+		writeDirectory: vi.fn(),
+		writeFile: vi.fn(),
+	},
 	runner: vi.fn(),
 	take: vi.fn(),
 };
diff --git a/packages/create/src/producers/producePreset.test.ts b/packages/create/src/producers/producePreset.test.ts
index 812282d8..08d6afd7 100644
--- a/packages/create/src/producers/producePreset.test.ts
+++ b/packages/create/src/producers/producePreset.test.ts
@@ -19,6 +19,7 @@ const system = {
 		octokit: {} as Octokit,
 	},
 	fs: {
+		readDirectory: vi.fn(),
 		readFile: vi.fn(),
 		writeDirectory: vi.fn(),
 		writeFile: vi.fn(),
diff --git a/packages/create/src/runners/applyFilesToSystem.ts b/packages/create/src/runners/applyFilesToSystem.ts
index f65038d9..60ed9184 100644
--- a/packages/create/src/runners/applyFilesToSystem.ts
+++ b/packages/create/src/runners/applyFilesToSystem.ts
@@ -1,11 +1,9 @@
+import { CreatedDirectory, WritingFileSystem } from "create-fs";
 import * as path from "node:path";
 import prettier from "prettier";
 
-import { CreatedFiles } from "../types/creations.js";
-import { WritingFileSystem } from "../types/system.js";
-
 export async function applyFilesToSystem(
-	files: CreatedFiles,
+	files: CreatedDirectory,
 	system: WritingFileSystem,
 	directory: string,
 ) {
@@ -45,7 +43,7 @@ function inferParser(fileName: string, text: string) {
 }
 
 async function writeToSystemWorker(
-	files: CreatedFiles,
+	files: CreatedDirectory,
 	system: WritingFileSystem,
 	basePath: string,
 ) {
diff --git a/packages/create/src/runners/runBlock.test.ts b/packages/create/src/runners/runBlock.test.ts
index 144bacd5..45e04bd3 100644
--- a/packages/create/src/runners/runBlock.test.ts
+++ b/packages/create/src/runners/runBlock.test.ts
@@ -18,6 +18,7 @@ function createSystem() {
 			octokit: {} as Octokit,
 		},
 		fs: {
+			readDirectory: noop("readDirectory"),
 			readFile: noop("readFile"),
 			writeDirectory: vi.fn(),
 			writeFile: vi.fn(),
diff --git a/packages/create/src/runners/runPreset.test.ts b/packages/create/src/runners/runPreset.test.ts
index b16e3840..c8b7bb4a 100644
--- a/packages/create/src/runners/runPreset.test.ts
+++ b/packages/create/src/runners/runPreset.test.ts
@@ -18,6 +18,7 @@ function createSystem() {
 			octokit: {} as Octokit,
 		},
 		fs: {
+			readDirectory: noop("readDirectory"),
 			readFile: noop("readFile"),
 			writeDirectory: vi.fn(),
 			writeFile: vi.fn(),
diff --git a/packages/create/src/system/createSystemContext.ts b/packages/create/src/system/createSystemContext.ts
index fd211fd9..e47b1724 100644
--- a/packages/create/src/system/createSystemContext.ts
+++ b/packages/create/src/system/createSystemContext.ts
@@ -1,10 +1,11 @@
+import { createWritingFileSystem } from "create-fs";
+
 import { TakeInput } from "../types/inputs.js";
 import { NativeSystem, SystemContext, SystemDisplay } from "../types/system.js";
 import { createOfflineFetchers } from "./createOfflineFetchers.js";
 import { createSystemDisplay } from "./createSystemDisplay.js";
 import { createSystemFetchers } from "./createSystemFetchers.js";
 import { createSystemRunner } from "./createSystemRunner.js";
-import { createWritingFileSystem } from "./createWritingFileSystem.js";
 
 export interface SystemContextSettings extends Partial<NativeSystem> {
 	auth?: string;
diff --git a/packages/create/src/system/createWritingFileSystem.ts b/packages/create/src/system/createWritingFileSystem.ts
deleted file mode 100644
index 4480eb46..00000000
--- a/packages/create/src/system/createWritingFileSystem.ts
+++ /dev/null
@@ -1,13 +0,0 @@
-import * as nodeFS from "node:fs/promises";
-
-export function createWritingFileSystem() {
-	return {
-		readFile: async (filePath: string) =>
-			(await nodeFS.readFile(filePath)).toString(),
-		writeDirectory: async (directoryPath: string) =>
-			void (await nodeFS.mkdir(directoryPath, { recursive: true })),
-		writeFile: async (filePath: string, contents: string) => {
-			await nodeFS.writeFile(filePath, contents);
-		},
-	};
-}
diff --git a/packages/create/src/types/creations.ts b/packages/create/src/types/creations.ts
index a6c30488..c796bc34 100644
--- a/packages/create/src/types/creations.ts
+++ b/packages/create/src/types/creations.ts
@@ -1,5 +1,4 @@
-// eslint-disable-next-line @eslint-community/eslint-comments/disable-enable-pair
-/* eslint-disable @typescript-eslint/consistent-indexed-object-style */
+import { CreatedDirectory } from "create-fs";
 
 import { BlockWithAddons } from "./blocks.js";
 import { SystemFetchers } from "./system.js";
@@ -12,25 +11,6 @@ export interface CreatedBlockAddons<
 	block: BlockWithAddons<Addons, Options>;
 }
 
-export type CreatedFileEntry =
-	| [string, CreatedFileOptions]
-	| [string]
-	| CreatedFiles
-	| false
-	| string;
-
-export interface CreatedFileOptions {
-	/**
-	 * File mode (permission and sticky bits) per chmod().
-	 * @example 0o777 for an executable file.
-	 */
-	mode?: number;
-}
-
-export interface CreatedFiles {
-	[i: string]: CreatedFileEntry | undefined;
-}
-
 export interface CreatedRequest {
 	id: string;
 	send: CreatedRequestSender;
@@ -49,7 +29,7 @@ export type Creation<Options extends object> = DirectCreation &
 	IndirectCreation<Options>;
 
 export interface DirectCreation {
-	files: CreatedFiles;
+	files: CreatedDirectory;
 	requests: CreatedRequest[];
 	scripts: CreatedScript[];
 }
diff --git a/packages/create/src/types/inputs.ts b/packages/create/src/types/inputs.ts
index 8254e0bb..b57866c8 100644
--- a/packages/create/src/types/inputs.ts
+++ b/packages/create/src/types/inputs.ts
@@ -1,8 +1,8 @@
+import { ReadingFileSystem } from "create-fs";
+
 import { TakeContext } from "./context.js";
 import { SystemFetchers, SystemRunner } from "./system.js";
 
-export type FileSystemReadFile = (filePath: string) => Promise<string>;
-
 export type Input<
 	Result,
 	Args extends object | undefined = undefined,
@@ -15,7 +15,7 @@ export type InputArgsFor<TypeofInput> =
 
 export interface InputContext extends TakeContext {
 	fetchers: SystemFetchers;
-	fs: InputFileSystem;
+	fs: ReadingFileSystem;
 	runner: SystemRunner;
 }
 
@@ -36,10 +36,6 @@ export interface InputContextWithArgs<Args extends object>
 	args: Args;
 }
 
-export interface InputFileSystem {
-	readFile: FileSystemReadFile;
-}
-
 export type InputWithArgs<Result, Args extends object> = (
 	context: InputContextWithArgs<Args>,
 ) => Result;
diff --git a/packages/create/src/types/system.ts b/packages/create/src/types/system.ts
index 4b7496b4..44fc833f 100644
--- a/packages/create/src/types/system.ts
+++ b/packages/create/src/types/system.ts
@@ -1,20 +1,8 @@
+import { WritingFileSystem } from "create-fs";
 import { ExecaError, Result } from "execa";
 import { Octokit } from "octokit";
 
 import { TakeContext } from "./context.js";
-import { InputFileSystem } from "./inputs.js";
-
-export type FileSystemWriteDirectory = (directoryPath: string) => Promise<void>;
-
-export type FileSystemWriteFile = (
-	filePath: string,
-	contents: string,
-	options?: FileSystemWriteFileOptions,
-) => Promise<void>;
-
-export interface FileSystemWriteFileOptions {
-	mode?: number;
-}
 
 export interface NativeSystem {
 	fetchers: SystemFetchers;
@@ -44,8 +32,3 @@ export interface SystemFetchers {
 }
 
 export type SystemRunner = (command: string) => Promise<ExecaError | Result>;
-
-export interface WritingFileSystem extends InputFileSystem {
-	writeDirectory: FileSystemWriteDirectory;
-	writeFile: FileSystemWriteFile;
-}
diff --git a/packages/site/astro.config.ts b/packages/site/astro.config.ts
index 45bddff4..effa898a 100644
--- a/packages/site/astro.config.ts
+++ b/packages/site/astro.config.ts
@@ -48,10 +48,19 @@ export default defineConfig({
 								{ label: "Creators", link: "engine/apis/creators" },
 								{ label: "Producers", link: "engine/apis/producers" },
 								{ label: "Runners", link: "engine/apis/runners" },
-								{ label: "Testers", link: "engine/apis/testers" },
 							],
 							label: "APIs",
 						},
+						{
+							items: [
+								{ label: "create-fs", link: "engine/packages/create-fs" },
+								{
+									label: "create-testers",
+									link: "engine/packages/create-testers",
+								},
+							],
+							label: "Packages",
+						},
 					],
 					label: "Templating Engine",
 				},
diff --git a/packages/site/src/content/docs/engine/packages/create-fs.mdx b/packages/site/src/content/docs/engine/packages/create-fs.mdx
new file mode 100644
index 00000000..57eb0ec5
--- /dev/null
+++ b/packages/site/src/content/docs/engine/packages/create-fs.mdx
@@ -0,0 +1,40 @@
+---
+title: create-fs
+---
+
+import { PackageManagers } from "starlight-package-managers";
+
+The file system used by <a href="https://create.bingo"><code>create</code></a>. 🗄️
+
+<PackageManagers type="add" pkg="create-fs" />
+
+The separate `create-fs` package includes types and utility functions for the file system used in [Runtime > Creations > `files`](https://www.create.bingo/engine/runtime/creations#files).
+
+This file system is a simplified abstraction over the lower-level APIs in Node.js and other platforms.
+APIs and data are optimized for simplicity and ease of use, rather than completeness.
+
+For example, given a structure like:
+
+```plaintext
+/
+└── README.md
+└── src
+    └── index.ts
+```
+
+`create-fs` would represent that structure with an object like:
+
+```json
+{
+	"README.md": "...",
+	"src": {
+		"index.ts": "..."
+	}
+}
+```
+
+## APIs
+
+### `intakeFromDirectory`
+
+Reads in the
diff --git a/packages/site/src/content/docs/engine/apis/testers.mdx b/packages/site/src/content/docs/engine/packages/create-testers.mdx
similarity index 98%
rename from packages/site/src/content/docs/engine/apis/testers.mdx
rename to packages/site/src/content/docs/engine/packages/create-testers.mdx
index d6cd6696..28dc3c4e 100644
--- a/packages/site/src/content/docs/engine/apis/testers.mdx
+++ b/packages/site/src/content/docs/engine/packages/create-testers.mdx
@@ -1,14 +1,16 @@
 ---
-title: Tester APIs
+title: create-testers
 ---
 
+import { PackageManagers } from "starlight-package-managers";
+
+Test utilities for composable, testable, type-safe templates. ⚗️
+
+<PackageManagers type="add" pkg="create-testers" dev />
+
 The separate `create-testers` package includes testing utilities that run [Producers](./producers) in fully virtualized environments.
 This is intended for use in unit tests that should mock out all [System Context](../runtime/contexts#system-contexts).
 
-```shell
-npm i create-testers -D
-```
-
 :::tip
 `create-testers` is test-framework-agnostic.
 You can use it with any typical testing framework, including [Jest](https://jestjs.io) and [Vitest](https://vitest.dev).
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index f2199078..0dd38316 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -116,6 +116,9 @@ importers:
       chalk:
         specifier: ^5.4.0
         version: 5.4.1
+      create-fs:
+        specifier: workspace:^
+        version: link:../create-fs
       execa:
         specifier: ^9.5.2
         version: 9.5.2
@@ -150,16 +153,47 @@ importers:
       '@types/hosted-git-info':
         specifier: 3.0.5
         version: 3.0.5
+      '@types/node':
+        specifier: ^22.10.5
+        version: 22.10.5
+
+  packages/create-fs:
+    dependencies:
+      create:
+        specifier: workspace:^
+        version: link:../create
+      octokit:
+        specifier: ^4.0.2
+        version: 4.0.2
+    devDependencies:
+      '@types/node':
+        specifier: ^22.10.5
+        version: 22.10.5
+      zod:
+        specifier: 3.24.1
+        version: 3.24.1
 
   packages/create-testers:
     dependencies:
       create:
         specifier: workspace:^
         version: link:../create
+      create-fs:
+        specifier: workspace:^
+        version: link:../create-fs
+      diff:
+        specifier: ^7.0.0
+        version: 7.0.0
       octokit:
         specifier: ^4.0.2
         version: 4.0.2
+      without-undefined-properties:
+        specifier: ^0.1.1
+        version: 0.1.1
     devDependencies:
+      '@types/diff':
+        specifier: ^7.0.0
+        version: 7.0.0
       zod:
         specifier: 3.24.1
         version: 3.24.1
@@ -1475,6 +1509,9 @@ packages:
   '@types/debug@4.1.12':
     resolution: {integrity: sha512-vIChWdVG3LG1SMxEvI/AK+FWJthlrqlTu7fbrlywTkkaONwk/UAGaULXRlf8vkzFBLVm0zkMdCquhL5aOjhXPQ==}
 
+  '@types/diff@7.0.0':
+    resolution: {integrity: sha512-sVpkpbnTJL9CYoDf4U+tHaQLe5HiTaHWY7m9FuYA7oMCHwC9ie0Vh9eIGapyzYrU3+pILlSY2fAc4elfw5m4dg==}
+
   '@types/eslint-plugin-markdown@2.0.2':
     resolution: {integrity: sha512-ImmEw5xBVb9vCaFfQ+5kUcVatUO4XPpTvryAmhpKzalUKhDb3EZmeuHvIUO6E1/WDOTw+/b9qlWsZhxULhZdfQ==}
 
@@ -1529,6 +1566,9 @@ packages:
   '@types/node@22.10.3':
     resolution: {integrity: sha512-DifAyw4BkrufCILvD3ucnuN8eydUfc/C1GlyrnI+LK6543w5/L3VeVgf05o3B4fqSXP1dKYLOZsKfutpxPzZrw==}
 
+  '@types/node@22.10.5':
+    resolution: {integrity: sha512-F8Q+SeGimwOo86fiovQh8qiXfFEh2/ocYv7tU5pJ3EXMSSxk1Joj5wefpFK2fHTf/N6HKGSxIDBT9f3gCxXPkQ==}
+
   '@types/normalize-package-data@2.4.4':
     resolution: {integrity: sha512-37i+OaWTh9qeK4LSHPsyRC7NahnGotNuZvjLSgcPzblpHB3rrCJxAOgI5gCdKm7coonsaX1Of0ILiTcnZjbfxA==}
 
@@ -2286,6 +2326,10 @@ packages:
     resolution: {integrity: sha512-uIFDxqpRZGZ6ThOk84hEfqWoHx2devRFvpTZcTHur85vImfaxUbTW9Ryh4CpCuDnToOP1CEtXKIgytHBPVff5A==}
     engines: {node: '>=0.3.1'}
 
+  diff@7.0.0:
+    resolution: {integrity: sha512-PJWHUb1RFevKCwaFA9RlG5tCd+FO5iRh9A8HEtkmBH2Li03iJriB6m6JIN4rGz3K3JLawI7/veA1xzRKP6ISBw==}
+    engines: {node: '>=0.3.1'}
+
   direction@2.0.1:
     resolution: {integrity: sha512-9S6m9Sukh1cZNknO1CWAr2QAWsbKLafQiyM5gZ7VgXHeuaoUwffKN4q6NC4A/Mf9iiPlOXQEKW/Mv/mh9/3YFA==}
     hasBin: true
@@ -6311,6 +6355,8 @@ snapshots:
     dependencies:
       '@types/ms': 0.7.34
 
+  '@types/diff@7.0.0': {}
+
   '@types/eslint-plugin-markdown@2.0.2':
     dependencies:
       '@types/eslint': 9.6.0
@@ -6369,11 +6415,15 @@ snapshots:
     dependencies:
       undici-types: 6.20.0
 
+  '@types/node@22.10.5':
+    dependencies:
+      undici-types: 6.20.0
+
   '@types/normalize-package-data@2.4.4': {}
 
   '@types/sax@1.2.7':
     dependencies:
-      '@types/node': 22.10.3
+      '@types/node': 22.10.5
 
   '@types/semver@7.5.8': {}
 
@@ -7281,6 +7331,8 @@ snapshots:
 
   diff@5.2.0: {}
 
+  diff@7.0.0: {}
+
   direction@2.0.1: {}
 
   dlv@1.1.3: {}
diff --git a/tsconfig.build.json b/tsconfig.build.json
index 90c8ebcc..72ded47f 100644
--- a/tsconfig.build.json
+++ b/tsconfig.build.json
@@ -7,6 +7,7 @@
 	"files": [],
 	"references": [
 		{ "path": "./packages/create" },
+		{ "path": "./packages/create-fs" },
 		{ "path": "./packages/create-testers" },
 		{ "path": "./packages/input-from-file" },
 		{ "path": "./packages/input-from-file-json" },

From dc69b141f7d217d3a2f8c7c68fb2ea4616d8e7ca Mon Sep 17 00:00:00 2001
From: Josh Goldberg <git@joshuakgoldberg.com>
Date: Tue, 14 Jan 2025 11:59:56 -0500
Subject: [PATCH 2/5] tests

---
 .../src/intake/intakeFromDirectory.test.ts    |  93 ++++++++++++++
 .../src/intake/intakeFromDirectory.ts         |   6 +-
 .../src/diffCreatedDirectory.test.ts          | 121 ++++++++++++++++++
 .../src/diffCreatedDirectory.ts               |  27 ++--
 4 files changed, 233 insertions(+), 14 deletions(-)
 create mode 100644 packages/create-fs/src/intake/intakeFromDirectory.test.ts
 create mode 100644 packages/create-testers/src/diffCreatedDirectory.test.ts

diff --git a/packages/create-fs/src/intake/intakeFromDirectory.test.ts b/packages/create-fs/src/intake/intakeFromDirectory.test.ts
new file mode 100644
index 00000000..0a5d4004
--- /dev/null
+++ b/packages/create-fs/src/intake/intakeFromDirectory.test.ts
@@ -0,0 +1,93 @@
+import { describe, expect, it, vi } from "vitest";
+
+import { intakeFromDirectory } from "./intakeFromDirectory.js";
+
+const mockReaddir = vi.fn();
+const mockReadFile = vi.fn();
+const mockStat = vi.fn();
+
+vi.mock("node:fs/promises", () => ({
+	get readdir() {
+		return mockReaddir;
+	},
+	get readFile() {
+		return mockReadFile;
+	},
+	get stat() {
+		return mockStat;
+	},
+}));
+
+describe("intakeFromDirectory", () => {
+	it("returns an empty object when the directory has no files", async () => {
+		mockReaddir.mockResolvedValueOnce([]);
+
+		const directory = await intakeFromDirectory("from", {
+			exclude: /excluded/,
+		});
+
+		expect(directory).toEqual({});
+		expect(mockReaddir.mock.calls).toEqual([["from"]]);
+		expect(mockStat).not.toHaveBeenCalled();
+	});
+
+	it("returns non-excluded files when the directory contains files", async () => {
+		mockReaddir.mockResolvedValueOnce(["excluded", "included-a", "included-b"]);
+		mockReadFile
+			.mockResolvedValueOnce("contents-a")
+			.mockResolvedValueOnce("contents-b");
+		mockStat
+			.mockResolvedValueOnce({
+				isDirectory: () => false,
+				mode: 123,
+			})
+			.mockResolvedValueOnce({
+				isDirectory: () => false,
+				mode: 456,
+			});
+
+		const directory = await intakeFromDirectory("from", {
+			exclude: /excluded/,
+		});
+
+		expect(directory).toEqual({
+			"included-a": ["contents-a", { mode: 123 }],
+			"included-b": ["contents-b", { mode: 456 }],
+		});
+		expect(mockReaddir.mock.calls).toEqual([["from"]]);
+		expect(mockStat.mock.calls).toEqual([
+			["from/included-a"],
+			["from/included-b"],
+		]);
+	});
+
+	it("returns a nested file when the directory contains a nested directory", async () => {
+		mockReaddir
+			.mockResolvedValueOnce(["middle"])
+			.mockResolvedValueOnce(["excluded", "included"]);
+		mockReadFile.mockResolvedValueOnce("contents");
+		mockStat
+			.mockResolvedValueOnce({
+				isDirectory: () => true,
+			})
+			.mockResolvedValueOnce({
+				isDirectory: () => false,
+				mode: 123,
+			});
+
+		const directory = await intakeFromDirectory("from", {
+			exclude: /excluded/,
+		});
+
+		expect(directory).toEqual({
+			middle: {
+				included: ["contents", { mode: 123 }],
+			},
+		});
+		expect(mockReaddir.mock.calls).toEqual([["from"], ["from/middle"]]);
+		expect(mockStat.mock.calls).toEqual([
+			["from/middle"],
+			["from/middle/included"],
+		]);
+	});
+});
diff --git a/packages/create-fs/src/intake/intakeFromDirectory.ts b/packages/create-fs/src/intake/intakeFromDirectory.ts
index 724dfe53..90198af4 100644
--- a/packages/create-fs/src/intake/intakeFromDirectory.ts
+++ b/packages/create-fs/src/intake/intakeFromDirectory.ts
@@ -11,7 +11,7 @@ export async function intakeFromDirectory(
 	directoryPath: string,
 	settings: IntakeFromDirectorySettings,
 ) {
-	const files: CreatedDirectory = {};
+	const directory: CreatedDirectory = {};
 	const children = await fs.readdir(directoryPath);
 
 	for (const child of children) {
@@ -22,10 +22,10 @@ export async function intakeFromDirectory(
 		const childPath = path.join(directoryPath, child);
 		const stat = await fs.stat(childPath);
 
-		files[child] = stat.isDirectory()
+		directory[child] = stat.isDirectory()
 			? await intakeFromDirectory(childPath, settings)
 			: [(await fs.readFile(childPath)).toString(), { mode: stat.mode }];
 	}
 
-	return files;
+	return directory;
 }
diff --git a/packages/create-testers/src/diffCreatedDirectory.test.ts b/packages/create-testers/src/diffCreatedDirectory.test.ts
new file mode 100644
index 00000000..45b73977
--- /dev/null
+++ b/packages/create-testers/src/diffCreatedDirectory.test.ts
@@ -0,0 +1,121 @@
+import { describe, expect, it, test, vi } from "vitest";
+
+import { diffCreatedDirectory } from "./diffCreatedDirectory.js";
+
+describe("diffCreatedDirectory", () => {
+	test.each([
+		[{}, {}, undefined],
+		[{}, { a: "" }, { a: "" }],
+		[{}, { a: { b: "" } }, { a: { b: "" } }],
+		[{ a: "" }, { a: "" }, undefined],
+		[
+			{ a: "" },
+			{ a: "b\n" },
+			{
+				a: `@@ -0,0 +1,1 @@
++b
+`,
+			},
+		],
+		[{ a: "b\n" }, { a: "b\n" }, undefined],
+		[{ a: "b\n" }, {}, undefined],
+		[{ a: "" }, { a: [""] }, undefined],
+		[{ a: "" }, { a: ["", { mode: undefined }] }, undefined],
+		[{ a: "" }, { a: ["", { mode: 123 }] }, undefined],
+		[{ a: [""] }, { a: ["", { mode: 123 }] }, undefined],
+		[
+			{ a: ["", { mode: undefined }] },
+			{ a: ["", { mode: undefined }] },
+			undefined,
+		],
+		[{ a: ["", { mode: undefined }] }, { a: ["", { mode: 123 }] }, undefined],
+		[{ a: ["", { mode: 123 }] }, { a: ["", { mode: 123 }] }, undefined],
+		[{ a: ["", { mode: 123 }] }, { a: [""] }, undefined],
+		[{ a: ["", { mode: 123 }] }, { a: ["", {}] }, undefined],
+		[{ a: ["", { mode: 123 }] }, { a: ["", { mode: undefined }] }, undefined],
+		[
+			{ a: ["", { mode: 123 }] },
+			{ a: ["", { mode: 456 }] },
+			{
+				a: [
+					undefined,
+					{
+						mode: `@@ -1,1 +1,1 @@
+-7b
+\\ No newline at end of file
++1c8
+\\ No newline at end of file
+`,
+					},
+				],
+			},
+		],
+		[
+			{ a: "" },
+			{ a: { b: {} } },
+			{ a: "Mismatched a: actual is string; created is object." },
+		],
+		[
+			{ a: [""] },
+			{ a: { b: {} } },
+			{ a: "Mismatched a: actual is created file; created is object." },
+		],
+		[{ a: [""] }, { a: "" }, undefined],
+		[
+			{ a: ["b\n"] },
+			{ a: "" },
+			{
+				a: `@@ -1,1 +0,0 @@
+-b
+`,
+			},
+		],
+		[
+			{ a: { b: {} } },
+			{ a: "" },
+			{ a: "Mismatched a: actual is object; created is string." },
+		],
+		[
+			{ a: { b: {} } },
+			{ a: [""] },
+			{ a: "Mismatched a: actual is object; created is created file." },
+		],
+		[{ a: "" }, { a: [""] }, undefined],
+		[{ a: { b: "c\n" } }, {}, undefined],
+		[{ a: { b: "c\n" } }, { b: {} }, undefined],
+		[{ a: { b: "c\n" } }, { a: { b: "c\n" } }, undefined],
+		[
+			{ a: { b: "c\n" } },
+			{ a: { b: "d\n" } },
+			{
+				a: {
+					b: `@@ -1,1 +1,1 @@
+-c
++d
+`,
+				},
+			},
+		],
+		[{ a: { b: "c\n" } }, { a: { d: "e\n" } }, { a: { d: "e\n" } }],
+		[
+			{ a: { b: { c: undefined } } },
+			{ a: { b: { c: { d: "e\n" } } } },
+			{ a: { b: { c: { d: "e\n" } } } },
+		],
+		[
+			{ a: { b: { c: { d: "e\n" } } } },
+			{ a: { b: { c: undefined } } },
+			undefined,
+		],
+		[{ a: { b: "c\n" } }, { a: { d: "e\n" } }, { a: { d: "e\n" } }],
+		[
+			{ a: { b: { c: { d: "e\n" } } } },
+			{ a: { b: { f: "g\n" } } },
+			{ a: { b: { f: "g\n" } } },
+		],
+	])("%j and %j", (actual, created, expected) => {
+		expect(diffCreatedDirectory(actual, created, (text) => text)).toEqual(
+			expected,
+		);
+	});
+});
diff --git a/packages/create-testers/src/diffCreatedDirectory.ts b/packages/create-testers/src/diffCreatedDirectory.ts
index e8e0f13b..5ce2bce7 100644
--- a/packages/create-testers/src/diffCreatedDirectory.ts
+++ b/packages/create-testers/src/diffCreatedDirectory.ts
@@ -12,8 +12,8 @@ export interface DiffedCreatedDirectory {
 }
 
 export type DiffedCreatedFileEntry =
-	| [string, DiffedCreatedFileOptions]
 	| [string]
+	| [string | undefined, DiffedCreatedFileOptions?]
 	| CreatedFileEntry
 	| DiffedCreatedDirectory
 	| string;
@@ -44,7 +44,7 @@ export function diffCreatedDirectoryWorker(
 
 	for (const [childName, childCreated] of Object.entries(created)) {
 		if (!(childName in actual)) {
-			result[childName] = childCreated;
+			result[childName] = undefinedIfEmpty(childCreated);
 			continue;
 		}
 
@@ -63,9 +63,7 @@ export function diffCreatedDirectoryWorker(
 		}
 	}
 
-	const trimmed = withoutUndefinedProperties(result);
-
-	return Object.keys(trimmed).length === 0 ? undefined : result;
+	return undefinedIfEmpty(withoutUndefinedProperties(result));
 }
 
 function diffCreatedDirectoryChild(
@@ -106,9 +104,8 @@ function diffCreatedDirectoryChild(
 				childCreated[1],
 				pathToChild,
 			);
-			return fileDiff || optionsDiff
-				? [fileDiff ?? "", optionsDiff ?? {}]
-				: undefined;
+
+			return (fileDiff ?? optionsDiff) ? [fileDiff, optionsDiff] : undefined;
 		}
 
 		if (typeof childCreated === "string") {
@@ -120,7 +117,7 @@ function diffCreatedDirectoryChild(
 			);
 		}
 
-		return `Mismatched ${pathToChild}: actual is a created file; created is ${typeof childCreated}.`;
+		return `Mismatched ${pathToChild}: actual is created file; created is ${typeof childCreated}.`;
 	}
 
 	if (Array.isArray(childCreated)) {
@@ -133,7 +130,7 @@ function diffCreatedDirectoryChild(
 			);
 		}
 
-		return `Mismatched ${pathToChild}: actual is ${typeof childActual}; created is a created file.`;
+		return `Mismatched ${pathToChild}: actual is ${typeof childActual}; created is created file.`;
 	}
 
 	if (typeof childActual === "object") {
@@ -164,8 +161,8 @@ function diffCreatedFileText(
 		: createTwoFilesPatch(
 				pathToFile,
 				pathToFile,
-				actualProcessed,
 				createdProcessed,
+				actualProcessed,
 			).replace(/^Index: .+\n=+\n-{3} .+\n\+{3} .+\n/gmu, "");
 }
 
@@ -196,3 +193,11 @@ function diffCreatedFileOptions(
 		),
 	};
 }
+function undefinedIfEmpty<T>(value: T) {
+	return !!value &&
+		typeof value === "object" &&
+		!Array.isArray(value) &&
+		Object.keys(value).length === 0
+		? undefined
+		: value;
+}

From 1c7e815e75d36c0d180203ace23f615f4f29c5c5 Mon Sep 17 00:00:00 2001
From: Josh Goldberg <git@joshuakgoldberg.com>
Date: Tue, 14 Jan 2025 12:19:56 -0500
Subject: [PATCH 3/5] docs

---
 .../src/intake/intakeFromDirectory.test.ts    | 34 ++++++++++++--
 .../src/intake/intakeFromDirectory.ts         |  6 +--
 .../src/diffCreatedDirectory.test.ts          | 12 ++++-
 .../docs/engine/packages/create-fs.mdx        | 30 +++++++++++-
 .../docs/engine/packages/create-testers.mdx   | 47 +++++++++++++++++++
 5 files changed, 120 insertions(+), 9 deletions(-)

diff --git a/packages/create-fs/src/intake/intakeFromDirectory.test.ts b/packages/create-fs/src/intake/intakeFromDirectory.test.ts
index 0a5d4004..6626f0c5 100644
--- a/packages/create-fs/src/intake/intakeFromDirectory.test.ts
+++ b/packages/create-fs/src/intake/intakeFromDirectory.test.ts
@@ -22,16 +22,42 @@ describe("intakeFromDirectory", () => {
 	it("returns an empty object when the directory has no files", async () => {
 		mockReaddir.mockResolvedValueOnce([]);
 
-		const directory = await intakeFromDirectory("from", {
-			exclude: /excluded/,
-		});
+		const directory = await intakeFromDirectory("from");
 
 		expect(directory).toEqual({});
 		expect(mockReaddir.mock.calls).toEqual([["from"]]);
 		expect(mockStat).not.toHaveBeenCalled();
 	});
 
-	it("returns non-excluded files when the directory contains files", async () => {
+	it("returns files when the directory contains files", async () => {
+		mockReaddir.mockResolvedValueOnce(["included-a", "included-b"]);
+		mockReadFile
+			.mockResolvedValueOnce("contents-a")
+			.mockResolvedValueOnce("contents-b");
+		mockStat
+			.mockResolvedValueOnce({
+				isDirectory: () => false,
+				mode: 123,
+			})
+			.mockResolvedValueOnce({
+				isDirectory: () => false,
+				mode: 456,
+			});
+
+		const directory = await intakeFromDirectory("from");
+
+		expect(directory).toEqual({
+			"included-a": ["contents-a", { mode: 123 }],
+			"included-b": ["contents-b", { mode: 456 }],
+		});
+		expect(mockReaddir.mock.calls).toEqual([["from"]]);
+		expect(mockStat.mock.calls).toEqual([
+			["from/included-a"],
+			["from/included-b"],
+		]);
+	});
+
+	it("returns non-excluded files when the directory contains files and excludes is provided", async () => {
 		mockReaddir.mockResolvedValueOnce(["excluded", "included-a", "included-b"]);
 		mockReadFile
 			.mockResolvedValueOnce("contents-a")
diff --git a/packages/create-fs/src/intake/intakeFromDirectory.ts b/packages/create-fs/src/intake/intakeFromDirectory.ts
index 90198af4..4c8cc829 100644
--- a/packages/create-fs/src/intake/intakeFromDirectory.ts
+++ b/packages/create-fs/src/intake/intakeFromDirectory.ts
@@ -4,18 +4,18 @@ import path from "node:path";
 import { CreatedDirectory } from "../types/files.js";
 
 export interface IntakeFromDirectorySettings {
-	exclude: RegExp;
+	exclude?: RegExp;
 }
 
 export async function intakeFromDirectory(
 	directoryPath: string,
-	settings: IntakeFromDirectorySettings,
+	settings: IntakeFromDirectorySettings = {},
 ) {
 	const directory: CreatedDirectory = {};
 	const children = await fs.readdir(directoryPath);
 
 	for (const child of children) {
-		if (settings.exclude.test(child)) {
+		if (settings.exclude?.test(child)) {
 			continue;
 		}
 
diff --git a/packages/create-testers/src/diffCreatedDirectory.test.ts b/packages/create-testers/src/diffCreatedDirectory.test.ts
index 45b73977..9a09f055 100644
--- a/packages/create-testers/src/diffCreatedDirectory.test.ts
+++ b/packages/create-testers/src/diffCreatedDirectory.test.ts
@@ -1,4 +1,4 @@
-import { describe, expect, it, test, vi } from "vitest";
+import { describe, expect, test } from "vitest";
 
 import { diffCreatedDirectory } from "./diffCreatedDirectory.js";
 
@@ -18,6 +18,16 @@ describe("diffCreatedDirectory", () => {
 			},
 		],
 		[{ a: "b\n" }, { a: "b\n" }, undefined],
+		[
+			{ a: "abc\n" },
+			{ a: "bbc\n" },
+			{
+				a: `@@ -1,1 +1,1 @@
+-abc
++bbc
+`,
+			},
+		],
 		[{ a: "b\n" }, {}, undefined],
 		[{ a: "" }, { a: [""] }, undefined],
 		[{ a: "" }, { a: ["", { mode: undefined }] }, undefined],
diff --git a/packages/site/src/content/docs/engine/packages/create-fs.mdx b/packages/site/src/content/docs/engine/packages/create-fs.mdx
index 57eb0ec5..213f51b4 100644
--- a/packages/site/src/content/docs/engine/packages/create-fs.mdx
+++ b/packages/site/src/content/docs/engine/packages/create-fs.mdx
@@ -37,4 +37,32 @@ For example, given a structure like:
 
 ### `intakeFromDirectory`
 
-Reads in the
+Given a directory path, reads in the directory as to the `create-fs` directory structure.
+
+```ts
+import { intakeFromDirectory } from "create-fs";
+
+// Result: { "index.ts": "..." }
+await intakeFromDirectory("src");
+```
+
+Parameters:
+
+1. `directoryPath: string` _(required)_
+2. `settings: IntakeFromDirectorySettings` _(optional)_:
+   - [`exclude: RegExp`](#intakefromdirectory-exclude)
+
+#### `exclude` {#intakefromdirectory-exclude}
+
+An optional regular expression to filter out directory children.
+
+For example, you may want to avoid `.git` and `node_modules` directories:
+
+```ts
+import { intakeFromDirectory } from "create-fs";
+
+// Result: { README.md: "...", src: { "index.ts": "..." }}
+await intakeFromDirectory(".", {
+	exclude: /node_modules|^\.git$/,
+});
+```
diff --git a/packages/site/src/content/docs/engine/packages/create-testers.mdx b/packages/site/src/content/docs/engine/packages/create-testers.mdx
index 28dc3c4e..a0fdf61d 100644
--- a/packages/site/src/content/docs/engine/packages/create-testers.mdx
+++ b/packages/site/src/content/docs/engine/packages/create-testers.mdx
@@ -16,6 +16,53 @@ This is intended for use in unit tests that should mock out all [System Context]
 You can use it with any typical testing framework, including [Jest](https://jestjs.io) and [Vitest](https://vitest.dev).
 :::
 
+## `diffCreatedDirectory`
+
+Produces a nested object diff comparing the [`files`](../runtime/creations#files) between an actual directory and produced results from a Creation.
+
+This is most commonly useful in conjunction with the [`create-fs` `intakeFromDirectory` API](./create-fs#intakefromdirectory).
+
+For example, this test snippet runs an integration test for a template repository, making sure its files on disk match its own `everything` Preset:
+
+```ts
+import { producePreset } from "create";
+import { intakeFromDirectory } from "create-fs";
+import { diffCreatedDirectory } from "create-testers";
+
+import { presetEverything } from "./presetEverything.js";
+
+const actual = await intakeFromDirectory(".", {
+	exclude: /node_modules|^\.git$/,
+});
+
+const created = await producePreset(presetEverything);
+
+expect(diffCreatedDirectory(actual, created)).toBeUndefined();
+```
+
+### DiffedCreatedDirectory
+
+`diffCreatedDirectory` will return an object matching a `DiffedCreatedDirectory` type.
+Any files that are different in the `created` argument compared to the `actual` argument will be included in that object.
+
+Differences are computed as:
+
+- If a file exists in `created` but not in `actual`, it will be included as-is
+- If a file exists in both but has different text content and/or `mode`, it will be included as a diff using [`diff`](https://www.npmjs.com/package/diff)'s `createTwoFilesPatch`, omitting headers before the `@@`
+
+For example, if a `src/index.ts` has content `abc` in `actual` but content `bbc` in `created`, the diff would look like:
+
+```js
+{
+	"src": {
+		"index.ts": `@@ -1,1 +1,1 @@
+-abc
++bbc
+`
+	}
+}
+```
+
 ## `testBase`
 
 For [Bases](../concepts/bases), a `testBase` function is exported that is analogous to [`produceBase`](./producers#producebase).

From 5c71675b9e8ea6c31f44bebbabde0b90ff45b8ba Mon Sep 17 00:00:00 2001
From: Josh Goldberg <git@joshuakgoldberg.com>
Date: Tue, 14 Jan 2025 12:22:26 -0500
Subject: [PATCH 4/5] lint and package touchups

---
 packages/create-fs/package.json               |  9 +--
 .../src/diffCreatedDirectory.ts               | 64 +++++++++----------
 pnpm-lock.yaml                                | 59 ++++++-----------
 3 files changed, 54 insertions(+), 78 deletions(-)

diff --git a/packages/create-fs/package.json b/packages/create-fs/package.json
index 2f35edf9..a7d4d1a1 100644
--- a/packages/create-fs/package.json
+++ b/packages/create-fs/package.json
@@ -23,15 +23,8 @@
 	"scripts": {
 		"build": "tsc"
 	},
-	"dependencies": {
-		"octokit": "^4.0.2"
-	},
 	"devDependencies": {
-		"@types/node": "^22.10.5",
-		"zod": "3.24.1"
-	},
-	"peerDependencies": {
-		"create": "workspace:^"
+		"@types/node": "^22.10.5"
 	},
 	"engines": {
 		"node": ">=18"
diff --git a/packages/create-testers/src/diffCreatedDirectory.ts b/packages/create-testers/src/diffCreatedDirectory.ts
index 5ce2bce7..172f3b77 100644
--- a/packages/create-testers/src/diffCreatedDirectory.ts
+++ b/packages/create-testers/src/diffCreatedDirectory.ts
@@ -34,38 +34,6 @@ export function diffCreatedDirectory(
 	return result && withoutUndefinedProperties(result);
 }
 
-export function diffCreatedDirectoryWorker(
-	actual: CreatedDirectory,
-	created: CreatedDirectory,
-	pathTo: string,
-	processText: ProcessText,
-): DiffedCreatedDirectory | undefined {
-	const result: DiffedCreatedDirectory = {};
-
-	for (const [childName, childCreated] of Object.entries(created)) {
-		if (!(childName in actual)) {
-			result[childName] = undefinedIfEmpty(childCreated);
-			continue;
-		}
-
-		const childActual = actual[childName];
-		const pathToChild = path.join(pathTo, childName);
-
-		const childDiffed = diffCreatedDirectoryChild(
-			childActual,
-			childCreated,
-			pathToChild,
-			processText,
-		);
-
-		if (childDiffed !== undefined) {
-			result[childName] = childDiffed;
-		}
-	}
-
-	return undefinedIfEmpty(withoutUndefinedProperties(result));
-}
-
 function diffCreatedDirectoryChild(
 	childActual: CreatedFileEntry | undefined,
 	childCreated: CreatedFileEntry | undefined,
@@ -147,6 +115,38 @@ function diffCreatedDirectoryChild(
 	return `Mismatched ${pathToChild}: actual is ${typeof childActual}; created is ${typeof childCreated}.`;
 }
 
+function diffCreatedDirectoryWorker(
+	actual: CreatedDirectory,
+	created: CreatedDirectory,
+	pathTo: string,
+	processText: ProcessText,
+): DiffedCreatedDirectory | undefined {
+	const result: DiffedCreatedDirectory = {};
+
+	for (const [childName, childCreated] of Object.entries(created)) {
+		if (!(childName in actual)) {
+			result[childName] = undefinedIfEmpty(childCreated);
+			continue;
+		}
+
+		const childActual = actual[childName];
+		const pathToChild = path.join(pathTo, childName);
+
+		const childDiffed = diffCreatedDirectoryChild(
+			childActual,
+			childCreated,
+			pathToChild,
+			processText,
+		);
+
+		if (childDiffed !== undefined) {
+			result[childName] = childDiffed;
+		}
+	}
+
+	return undefinedIfEmpty(withoutUndefinedProperties(result));
+}
+
 function diffCreatedFileText(
 	actual: string,
 	created: string,
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 0dd38316..597e0667 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -158,20 +158,10 @@ importers:
         version: 22.10.5
 
   packages/create-fs:
-    dependencies:
-      create:
-        specifier: workspace:^
-        version: link:../create
-      octokit:
-        specifier: ^4.0.2
-        version: 4.0.2
     devDependencies:
       '@types/node':
         specifier: ^22.10.5
         version: 22.10.5
-      zod:
-        specifier: 3.24.1
-        version: 3.24.1
 
   packages/create-testers:
     dependencies:
@@ -247,19 +237,19 @@ importers:
         version: 0.9.4(prettier-plugin-astro@0.14.1)(prettier@3.4.2)(typescript@5.7.2)
       '@astrojs/starlight':
         specifier: ^0.30.3
-        version: 0.30.3(astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))
+        version: 0.30.3(astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))
       '@types/node':
         specifier: ^22.10.3
-        version: 22.10.3
+        version: 22.10.5
       astro:
         specifier: ^5.1.1
-        version: 5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)
+        version: 5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)
       remark-custom-heading-id:
         specifier: ^2.0.0
         version: 2.0.0
       starlight-package-managers:
         specifier: ^0.8.1
-        version: 0.8.1(@astrojs/starlight@0.30.3(astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)))
+        version: 0.8.1(@astrojs/starlight@0.30.3(astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)))
       typescript:
         specifier: ^5.7.2
         version: 5.7.2
@@ -1563,9 +1553,6 @@ packages:
   '@types/node@22.10.2':
     resolution: {integrity: sha512-Xxr6BBRCAOQixvonOye19wnzyDiUtTeqldOOmj3CkeblonbccA12PFwlufvRdrpjXxqnmUaeiU5EOA+7s5diUQ==}
 
-  '@types/node@22.10.3':
-    resolution: {integrity: sha512-DifAyw4BkrufCILvD3ucnuN8eydUfc/C1GlyrnI+LK6543w5/L3VeVgf05o3B4fqSXP1dKYLOZsKfutpxPzZrw==}
-
   '@types/node@22.10.5':
     resolution: {integrity: sha512-F8Q+SeGimwOo86fiovQh8qiXfFEh2/ocYv7tU5pJ3EXMSSxk1Joj5wefpFK2fHTf/N6HKGSxIDBT9f3gCxXPkQ==}
 
@@ -5223,12 +5210,12 @@ snapshots:
     transitivePeerDependencies:
       - supports-color
 
-  '@astrojs/mdx@4.0.2(astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))':
+  '@astrojs/mdx@4.0.2(astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))':
     dependencies:
       '@astrojs/markdown-remark': 6.0.1
       '@mdx-js/mdx': 3.1.0(acorn@8.14.0)
       acorn: 8.14.0
-      astro: 5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)
+      astro: 5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)
       es-module-lexer: 1.5.4
       estree-util-visit: 2.0.0
       hast-util-to-html: 9.0.4
@@ -5252,16 +5239,16 @@ snapshots:
       stream-replace-string: 2.0.0
       zod: 3.24.1
 
-  '@astrojs/starlight@0.30.3(astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))':
+  '@astrojs/starlight@0.30.3(astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))':
     dependencies:
-      '@astrojs/mdx': 4.0.2(astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))
+      '@astrojs/mdx': 4.0.2(astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))
       '@astrojs/sitemap': 3.1.6
       '@pagefind/default-ui': 1.1.0
       '@types/hast': 3.0.4
       '@types/js-yaml': 4.0.9
       '@types/mdast': 4.0.4
-      astro: 5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)
-      astro-expressive-code: 0.38.3(astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))
+      astro: 5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)
+      astro-expressive-code: 0.38.3(astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))
       bcp-47: 2.1.0
       hast-util-from-html: 2.0.3
       hast-util-select: 6.0.2
@@ -6411,10 +6398,6 @@ snapshots:
     dependencies:
       undici-types: 6.20.0
 
-  '@types/node@22.10.3':
-    dependencies:
-      undici-types: 6.20.0
-
   '@types/node@22.10.5':
     dependencies:
       undici-types: 6.20.0
@@ -6708,12 +6691,12 @@ snapshots:
 
   astring@1.8.6: {}
 
-  astro-expressive-code@0.38.3(astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)):
+  astro-expressive-code@0.38.3(astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)):
     dependencies:
-      astro: 5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)
+      astro: 5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1)
       rehype-expressive-code: 0.38.3
 
-  astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1):
+  astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1):
     dependencies:
       '@astrojs/compiler': 2.10.3
       '@astrojs/internal-helpers': 0.4.2
@@ -6765,8 +6748,8 @@ snapshots:
       unist-util-visit: 5.0.0
       unstorage: 1.14.2
       vfile: 6.0.3
-      vite: 6.0.6(@types/node@22.10.3)(jiti@2.4.1)(yaml@2.6.1)
-      vitefu: 1.0.4(vite@6.0.6(@types/node@22.10.3)(jiti@2.4.1)(yaml@2.6.1))
+      vite: 6.0.6(@types/node@22.10.5)(jiti@2.4.1)(yaml@2.6.1)
+      vitefu: 1.0.4(vite@6.0.6(@types/node@22.10.5)(jiti@2.4.1)(yaml@2.6.1))
       which-pm: 3.0.0
       xxhash-wasm: 1.1.0
       yargs-parser: 21.1.1
@@ -10174,9 +10157,9 @@ snapshots:
 
   stackback@0.0.2: {}
 
-  starlight-package-managers@0.8.1(@astrojs/starlight@0.30.3(astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))):
+  starlight-package-managers@0.8.1(@astrojs/starlight@0.30.3(astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))):
     dependencies:
-      '@astrojs/starlight': 0.30.3(astro@5.1.1(@types/node@22.10.3)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))
+      '@astrojs/starlight': 0.30.3(astro@5.1.1(@types/node@22.10.5)(jiti@2.4.1)(rollup@4.29.1)(typescript@5.7.2)(yaml@2.6.1))
 
   std-env@3.8.0: {}
 
@@ -10519,20 +10502,20 @@ snapshots:
       '@types/node': 22.10.2
       fsevents: 2.3.3
 
-  vite@6.0.6(@types/node@22.10.3)(jiti@2.4.1)(yaml@2.6.1):
+  vite@6.0.6(@types/node@22.10.5)(jiti@2.4.1)(yaml@2.6.1):
     dependencies:
       esbuild: 0.24.2
       postcss: 8.4.49
       rollup: 4.29.1
     optionalDependencies:
-      '@types/node': 22.10.3
+      '@types/node': 22.10.5
       fsevents: 2.3.3
       jiti: 2.4.1
       yaml: 2.6.1
 
-  vitefu@1.0.4(vite@6.0.6(@types/node@22.10.3)(jiti@2.4.1)(yaml@2.6.1)):
+  vitefu@1.0.4(vite@6.0.6(@types/node@22.10.5)(jiti@2.4.1)(yaml@2.6.1)):
     optionalDependencies:
-      vite: 6.0.6(@types/node@22.10.3)(jiti@2.4.1)(yaml@2.6.1)
+      vite: 6.0.6(@types/node@22.10.5)(jiti@2.4.1)(yaml@2.6.1)
 
   vitest@2.1.8(@types/node@22.10.2):
     dependencies:

From b8385fb9c76c40b19fa400c406c3083f63e2ec46 Mon Sep 17 00:00:00 2001
From: Josh Goldberg <git@joshuakgoldberg.com>
Date: Tue, 14 Jan 2025 13:07:25 -0500
Subject: [PATCH 5/5] Exclude file system creators from coverage

---
 vitest.config.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/vitest.config.ts b/vitest.config.ts
index 8a48530f..faec7445 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -10,6 +10,7 @@ export default defineConfig({
 				"**/*.astro",
 				"**/vitest.*.ts",
 				"packages/*/src/index.ts",
+				"packages/create-fs/src/create*FileSystem.ts",
 				"packages/site/astro.config.ts",
 				"packages/site/src/content",
 			],