Fail the Windows build if provider prune leaves a target

`pruneUnusedProviders` now returns the directories it couldn't remove, and the
Forge hook throws on `win32` when any remain. A leftover provider tree there
resurfaces as the very `PathTooLongException` the prune prevents, so surfacing
the offending paths up front beats a later opaque Squirrel crash. Other
platforms still tolerate a stuck removal — it's only a size optimization there.

Addresses Copilot review on #3735.

---

Generated with the help of Claude Code, https://claude.com/claude-code

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: mokagio

apps/studio/forge.config.ts

@@ -283,7 +283,16 @@ const config: ForgeConfig = {
 			// and @mistralai's ~200-char generated filenames, nested under pi-coding-agent, blow
 			// past Windows' 260-char path limit and crash the Squirrel maker.
 			console.log( 'Removing unused AI provider SDKs from CLI bundle...' );
-			pruneUnusedProviders( cliNodeModules );
+			const unprunedProviders = pruneUnusedProviders( cliNodeModules );
+			if ( platform === 'win32' && unprunedProviders.length > 0 ) {
+				// A leftover provider tree on Windows resurfaces as the PathTooLongException the
+				// prune exists to prevent — fail now with the offending paths instead of letting
+				// the Squirrel maker crash later with no context.
+				throw new Error(
+					`Could not prune ${ unprunedProviders.length } provider director(ies) that exceed ` +
+						`Windows' 260-char path limit: ${ unprunedProviders.join( ', ' ) }`
+				);
+			}
 
 			console.log( `Downloading Node.js binary for ${ platform }-${ arch }...` );
 			await execAsync( [

scripts/remove-unused-ai-providers.test.ts

@@ -1,4 +1,4 @@
-import { existsSync, mkdirSync, mkdtempSync, rmSync, writeFileSync } from 'fs';
+import { chmodSync, existsSync, mkdirSync, mkdtempSync, rmSync, writeFileSync } from 'fs';
 import { tmpdir } from 'os';
 import { join } from 'path';
 import { afterEach, beforeEach, describe, expect, it } from 'vitest';
@@ -32,7 +32,7 @@ describe( 'pruneUnusedProviders', () => {
 		touch( '@smithy', 'node-http-handler', 'package.json' );
 		touch( '@google', 'genai', 'package.json' );
 
-		pruneUnusedProviders( nm );
+		expect( pruneUnusedProviders( nm ) ).toEqual( [] );
 
 		expect( has( '@mistralai' ) ).toBe( false );
 		expect( has( '@aws-sdk' ) ).toBe( false );
@@ -70,6 +70,19 @@ describe( 'pruneUnusedProviders', () => {
 	} );
 
 	it( 'is a no-op when the node_modules directory is absent', () => {
-		expect( () => pruneUnusedProviders( join( root, 'missing' ) ) ).not.toThrow();
+		expect( pruneUnusedProviders( join( root, 'missing' ) ) ).toEqual( [] );
+	} );
+
+	// A failed removal can't be induced portably; deletion permission lives on the parent
+	// directory, which behaves differently on Windows and is ignored when running as root.
+	const canInduceRemovalFailure = process.platform !== 'win32' && process.getuid?.() !== 0;
+	it.runIf( canInduceRemovalFailure )( 'returns targets it could not remove', () => {
+		touch( '@mistralai', 'mistralai', 'package.json' );
+		chmodSync( nm, 0o555 ); // read-only parent → the child can't be unlinked
+		try {
+			expect( pruneUnusedProviders( nm ) ).toEqual( [ join( nm, '@mistralai' ) ] );
+		} finally {
+			chmodSync( nm, 0o755 ); // restore so afterEach can clean up
+		}
 	} );
 } );

scripts/remove-unused-ai-providers.ts

@@ -29,7 +29,10 @@ const UNUSED_PROVIDER_DIRS = [
 	join( '@google', 'genai' ),
 ];
 
-function removeTargets( nodeModulesDir: string ): void {
+// Returns the directories that should have been removed but couldn't, so the caller can decide
+// how to react (the Forge hook fails the Windows build on any leftover — see pruneUnusedProviders).
+function removeTargets( nodeModulesDir: string ): string[] {
+	const failed: string[] = [];
 	for ( const target of UNUSED_PROVIDER_DIRS ) {
 		const dir = join( nodeModulesDir, target );
 		try {
@@ -43,36 +46,40 @@ function removeTargets( nodeModulesDir: string ): void {
 			rmSync( dir, { recursive: true, force: true } );
 			console.log( `Removed ${ target } from ${ nodeModulesDir }` );
 		} catch ( e ) {
-			// Tolerate transient failures (Windows AV locks, permissions). This is a size /
-			// path-length optimization; aborting packaging over a stuck file would be worse.
+			// Don't abort here: on a transient lock (Windows AV, permissions) other targets may
+			// still be removable, and the caller decides whether a leftover is fatal.
 			console.warn(
 				`Could not remove ${ target } from ${ nodeModulesDir }: ${
 					e instanceof Error ? e.message : String( e )
 				}`
 			);
+			failed.push( dir );
 		}
 	}
+	return failed;
 }
 
 /**
  * Walks the dependency tree and prunes the unused providers from every node_modules it finds —
- * the hoisted one and any nested under packages such as pi-coding-agent.
+ * the hoisted one and any nested under packages such as pi-coding-agent. Returns the directories
+ * that were targeted but couldn't be removed; on Windows a non-empty result is fatal, because a
+ * leftover provider tree resurfaces as the very `PathTooLongException` this prune prevents.
  */
-export function pruneUnusedProviders( nodeModulesDir: string ): void {
+export function pruneUnusedProviders( nodeModulesDir: string ): string[] {
 	// Most packages have no nested node_modules; recursion bottoms out here. Check existence
 	// up front so the common case is a cheap stat rather than a thrown-and-caught ENOENT.
 	if ( ! existsSync( nodeModulesDir ) ) {
-		return;
+		return [];
 	}
 
 	let entries;
 	try {
 		entries = readdirSync( nodeModulesDir, { withFileTypes: true } );
 	} catch {
-		return; // unreadable (permissions, races) — skip rather than abort packaging
+		return []; // unreadable (permissions, races) — skip rather than abort packaging
 	}
 
-	removeTargets( nodeModulesDir );
+	const failed = removeTargets( nodeModulesDir );
 
 	for ( const entry of entries ) {
 		if ( ! entry.isDirectory() ) {
@@ -89,11 +96,13 @@ export function pruneUnusedProviders( nodeModulesDir: string ): void {
 			}
 			for ( const scoped of scopedEntries ) {
 				if ( scoped.isDirectory() ) {
-					pruneUnusedProviders( join( packageDir, scoped.name, 'node_modules' ) );
+					failed.push( ...pruneUnusedProviders( join( packageDir, scoped.name, 'node_modules' ) ) );
 				}
 			}
 			continue;
 		}
-		pruneUnusedProviders( join( packageDir, 'node_modules' ) );
+		failed.push( ...pruneUnusedProviders( join( packageDir, 'node_modules' ) ) );
 	}
+
+	return failed;
 }