Fix user binstubs not on PATH and fix PATH order

buildpacks/ruby/CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Executables from the applications `bin` directory will be placed on the path before dependencies installed via bundler ([#383](https://github.com/heroku/buildpacks-ruby/pull/383))
+- Binaries from user installed gems will be placed on the path before binaries that ship with Ruby ([#383](https://github.com/heroku/buildpacks-ruby/pull/383))
+
 ## [5.0.0] - 2024-12-17
 
 ### Changed

buildpacks/ruby/Cargo.toml

@@ -34,3 +34,4 @@ cache_diff = { version = "1.0.0", features = ["bullet_stream"] }
 
 [dev-dependencies]
 libcnb-test = "=0.26.1"
+pretty_assertions = "1.4.1"

buildpacks/ruby/src/layers/bundle_install_layer.rs

@@ -322,9 +322,9 @@ fn display_name(cmd: &mut Command, env: &Env) -> String {
 
 #[cfg(test)]
 mod test {
-    use bullet_stream::strip_ansi;
-
     use super::*;
+    use bullet_stream::strip_ansi;
+    use pretty_assertions::assert_eq;
     use std::path::PathBuf;
 
     /// `CacheDiff` logic controls cache invalidation

buildpacks/ruby/src/layers/metrics_agent_install.rs

@@ -152,10 +152,10 @@ fn write_execd_script(
     fs_err::write(
         &execd,
         format!(
-            r#"#!/usr/bin/env bash
+            r"#!/usr/bin/env bash
 
                {daemon} --log {log} --loop-path {run_loop} --agentmon {agentmon}
-              "#,
+              ",
             log = log.display(),
             daemon = daemon.display(),
             run_loop = run_loop.display(),

buildpacks/ruby/src/layers/ruby_install_layer.rs

@@ -20,7 +20,7 @@ use bullet_stream::state::SubBullet;
 use bullet_stream::Print;
 use cache_diff::CacheDiff;
 use commons::gemfile_lock::ResolvedRubyVersion;
-use commons::layer::diff_migrate::DiffMigrateLayer;
+use commons::layer::diff_migrate::{DiffMigrateLayer, LayerRename};
 use flate2::read::GzDecoder;
 use libcnb::data::layer_name;
 use libcnb::layer::{EmptyLayerCause, LayerState};
@@ -42,7 +42,14 @@ pub(crate) fn handle(
         build: true,
         launch: true,
     }
-    .cached_layer(layer_name!("ruby"), context, metadata)?;
+    .cached_layer_rename(
+        LayerRename {
+            to: layer_name!("binruby"),
+            from: vec![layer_name!("ruby")],
+        },
+        context,
+        metadata,
+    )?;
     match &layer_ref.state {
         LayerState::Restored { cause } => {
             bullet = bullet.sub_bullet(cause);

buildpacks/ruby/src/main.rs

@@ -11,9 +11,11 @@ use layers::{
 use libcnb::build::{BuildContext, BuildResult, BuildResultBuilder};
 use libcnb::data::build_plan::BuildPlanBuilder;
 use libcnb::data::launch::LaunchBuilder;
+use libcnb::data::layer_name;
 use libcnb::detect::{DetectContext, DetectResult, DetectResultBuilder};
 use libcnb::generic::{GenericMetadata, GenericPlatform};
-use libcnb::layer_env::Scope;
+use libcnb::layer::UncachedLayerDefinition;
+use libcnb::layer_env::{LayerEnv, ModificationBehavior, Scope};
 use libcnb::Platform;
 use libcnb::{buildpack_main, Buildpack};
 use std::io::stdout;
@@ -28,6 +30,8 @@ mod user_errors;
 
 #[cfg(test)]
 use libcnb_test as _;
+#[cfg(test)]
+use pretty_assertions as _;
 
 use clap as _;
 
@@ -218,6 +222,28 @@ impl Buildpack for RubyBuildpack {
             (bullet.done(), layer_env.apply(Scope::Build, &env))
         };
 
+        env = {
+            let user_binstubs = context.uncached_layer(
+                layer_name!("user_binstubs"),
+                UncachedLayerDefinition {
+                    build: true,
+                    launch: true,
+                },
+            )?;
+            user_binstubs.write_env(
+                LayerEnv::new()
+                    .chainable_insert(Scope::All, ModificationBehavior::Delimiter, "PATH", ":")
+                    .chainable_insert(
+                        Scope::All,
+                        ModificationBehavior::Prepend,
+                        "PATH",
+                        context.app_dir.join("bin"),
+                    ),
+            )?;
+
+            user_binstubs.read_env()?.apply(Scope::Build, &env)
+        };
+
         // ## Detect gems
         let (mut build_output, gem_list, default_process) = {
             let bullet = build_output.bullet("Default process detection");

buildpacks/ruby/src/rake_task_detect.rs

@@ -29,10 +29,8 @@ pub(crate) fn call<T: IntoIterator<Item = (K, V)>, K: AsRef<OsStr>, V: AsRef<OsS
     envs: T,
     error_on_failure: bool,
 ) -> Result<(Print<SubBullet<Stdout>>, RakeDetect), CmdError> {
-    let mut cmd = Command::new("bundle");
-    cmd.args(["exec", "rake", "-P", "--trace"])
-        .env_clear()
-        .envs(envs);
+    let mut cmd = Command::new("rake");
+    cmd.args(["-P", "--trace"]).env_clear().envs(envs);
 
     let timer = bullet.start_timer(format!("Running {}", style::command(cmd.name())));
     let output = cmd.named_output().or_else(|error| {

buildpacks/ruby/src/steps/rake_assets_install.rs

@@ -20,7 +20,7 @@ pub(crate) fn rake_assets_install(
     let cases = asset_cases(rake_detect);
     let rake_assets_precompile = style::value("rake assets:precompile");
     let rake_assets_clean = style::value("rake assets:clean");
-    let rake_detect_cmd = style::value("bundle exec rake -P");
+    let rake_detect_cmd = style::value("rake -P");
 
     match cases {
         AssetCases::None => {
@@ -33,8 +33,8 @@ pub(crate) fn rake_assets_install(
                 format!("Compiling assets without cache (Clean task not found via {rake_detect_cmd})"),
             ).sub_bullet(format!("{help} Enable caching by ensuring {rake_assets_clean} is present when running the detect command locally"));
 
-            let mut cmd = Command::new("bundle");
-            cmd.args(["exec", "rake", "assets:precompile", "--trace"])
+            let mut cmd = Command::new("rake");
+            cmd.args(["assets:precompile", "--trace"])
                 .env_clear()
                 .envs(env);
 
@@ -79,16 +79,10 @@ pub(crate) fn rake_assets_install(
                 });
             }
 
-            let mut cmd = Command::new("bundle");
-            cmd.args([
-                "exec",
-                "rake",
-                "assets:precompile",
-                "assets:clean",
-                "--trace",
-            ])
-            .env_clear()
-            .envs(env);
+            let mut cmd = Command::new("rake");
+            cmd.args(["assets:precompile", "assets:clean", "--trace"])
+                .env_clear()
+                .envs(env);
 
             bullet
                 .stream_with(