[types] [doc] [fix] Make sure product_id is given preference + Update…

… readme file formatting + Mark some interfaces as internal.

README.md

@@ -296,15 +296,15 @@ export default function App() {
 
 ## Testing with the Sandbox
 
-This sample code uses PHP to generate the token and timestamp but you can 
-use the same approach in any server-side environment which will protect 
-the secret key.
+This sample code uses PHP to generate the token and timestamp but you can use
+the same approach in any server-side environment which will protect the secret
+key.
 
 1. Go to the Developer Dashboard.
 2. Under Plans click on the "Get Checkout Code" button.
 3. Go to the Sandbox tab.
-4. Copy the code to generate the `sandbox_token` and `timestamp` values and 
-output them for the Javascript to use.
+4. Copy the code to generate the `sandbox_token` and `timestamp` values and
+   output them for the Javascript to use.
 
 Example:
 
@@ -324,13 +324,12 @@ $sandbox_token = md5(
 );
 ```
 
-
 ```js
 const config = {
     // ...
     sandbox: {
         token: '<?php echo $sandbox_token; ?>',
-        ctx: '<?php echo $timestamp; ?>'
+        ctx: '<?php echo $timestamp; ?>',
     },
 };
 ```

src/lib/checkout.spec.ts

@@ -223,4 +223,24 @@ describe('CheckoutPopup', () => {
 
         expect(new URL(iFrame.src).searchParams.get('plugin_id')).toBe('1');
     });
+
+    test('prefers product_id over plugin_id', () => {
+        const checkout = new Checkout({
+            plugin_id: 1,
+            product_id: 2,
+            public_key: 'pk_123456',
+            license_key: 'sk_R-5E2+%20BD:.kp*(Oq2aodhzZ1Jw',
+        } as any);
+        checkout.open();
+
+        const guid = checkout.getGuid();
+
+        const iFrame = screen.queryByTestId(
+            `fs-checkout-page-${guid}`
+        ) as HTMLIFrameElement;
+
+        expect(iFrame).toBeInTheDocument();
+
+        expect(new URL(iFrame.src).searchParams.get('plugin_id')).toBe('2');
+    });
 });

src/lib/checkout.ts

@@ -53,7 +53,7 @@ export class Checkout {
         this.options = {
             ...popupOptions,
             public_key,
-            plugin_id: plugin_id ?? product_id,
+            plugin_id: product_id ?? plugin_id,
         };
 
         this.guid = generateGuid();

src/lib/contracts/CheckoutPopupOptions.ts

@@ -417,13 +417,17 @@ export interface CheckoutPopupEvents {
 
 /**
  * All options (parameters and events) required and supported by the Freemius Checkout.
+ *
+ * @internal
  */
 export interface CheckoutPopupOptions
     extends CheckoutPopupParams,
         CheckoutPopupEvents {}
 
 /**
  * Accept any arbitrary key-value pair to be passed to the checkout.
+ *
+ * @internal
  */
 export interface CheckoutPopupArbitraryParams {
     [key: Exclude<string, keyof CheckoutPopupOptions>]: any;