fix(@angular/build): exclude all entrypoints of a library from prebundling

The configuration now ensures that when a package is listed for exclusion, all paths within that package including sub-paths like `@foo/bar/baz`  are marked as external and not prebundled by the development server.

For example, specifying `@foo/bar` in the exclude list will prevent the development server from bundling any files from the `@foo/bar` package, including its sub-paths such as `@foo/bar/baz`.

This aligns with esbuild external option behaviour https://esbuild.github.io/api/#external

Closes angular#29170

Author: alan-agius4

packages/angular/build/src/builders/application/schema.json

@@ -196,7 +196,7 @@
       "additionalProperties": false
     },
     "externalDependencies": {
-      "description": "Exclude the listed external dependencies from being bundled into the bundle. Instead, the created bundle relies on these dependencies to be available during runtime.",
+      "description": "Exclude the listed external dependencies from being bundled into the bundle. Instead, the created bundle relies on these dependencies to be available during runtime. Note: `@foo/bar` marks all paths within the `@foo/bar` package as external, including sub-paths like `@foo/bar/baz`.",
       "type": "array",
       "items": {
         "type": "string"

packages/angular/build/src/builders/dev-server/schema.json

@@ -115,7 +115,7 @@
           "type": "object",
           "properties": {
             "exclude": {
-              "description": "List of package imports that should not be prebundled by the development server. The packages will be bundled into the application code itself.",
+              "description": "List of package imports that should not be prebundled by the development server. The packages will be bundled into the application code itself. Note: specifying `@foo/bar` marks all paths within the `@foo/bar` package as excluded, including sub-paths like `@foo/bar/baz`.",
               "type": "array",
               "items": { "type": "string" }
             }

packages/angular/build/src/builders/dev-server/tests/behavior/build-external-dependencies_spec.ts

@@ -15,7 +15,7 @@ describeServeBuilder(executeDevServer, DEV_SERVER_BUILDER_INFO, (harness, setupT
   describe('Behavior: "browser builder external dependencies"', () => {
     beforeEach(async () => {
       setupTarget(harness, {
-        externalDependencies: ['rxjs', 'rxjs/operators'],
+        externalDependencies: ['rxjs'],
       });
 
       await harness.writeFile(
@@ -48,7 +48,7 @@ describeServeBuilder(executeDevServer, DEV_SERVER_BUILDER_INFO, (harness, setupT
 
     it('respects import specifiers when using baseHref with trailing slash', async () => {
       setupTarget(harness, {
-        externalDependencies: ['rxjs', 'rxjs/operators'],
+        externalDependencies: ['rxjs'],
         baseHref: '/test/',
       });
 
@@ -67,7 +67,7 @@ describeServeBuilder(executeDevServer, DEV_SERVER_BUILDER_INFO, (harness, setupT
 
     it('respects import specifiers when using baseHref without trailing slash', async () => {
       setupTarget(harness, {
-        externalDependencies: ['rxjs', 'rxjs/operators'],
+        externalDependencies: ['rxjs/*'],
         baseHref: '/test',
       });
 

packages/angular/build/src/tools/esbuild/external-packages-plugin.ts

@@ -19,7 +19,9 @@ const EXTERNAL_PACKAGE_RESOLUTION = Symbol('EXTERNAL_PACKAGE_RESOLUTION');
  * @returns An esbuild plugin.
  */
 export function createExternalPackagesPlugin(options?: { exclude?: string[] }): Plugin {
-  const exclusions = options?.exclude?.length ? new Set(options.exclude) : undefined;
+  const exclusions = options?.exclude?.map((e) => (e.endsWith('/*') ? e.slice(0, -2) : e));
+  const seenExclusion: Set<string> = new Set();
+  const seenNonExclusions: Set<string> = new Set();
 
   return {
     name: 'angular-external-packages',
@@ -33,7 +35,7 @@ export function createExternalPackagesPlugin(options?: { exclude?: string[] }):
           .map(([key]) => key);
 
       // Safe to use native packages external option if no loader options or exclusions present
-      if (!exclusions && !loaderOptionKeys?.length) {
+      if (!exclusions?.length && !loaderOptionKeys?.length) {
         build.initialOptions.packages = 'external';
 
         return;
@@ -47,10 +49,23 @@ export function createExternalPackagesPlugin(options?: { exclude?: string[] }):
           return null;
         }
 
-        if (exclusions?.has(args.path)) {
+        if (seenExclusion.has(args.path)) {
           return null;
         }
 
+        if (!seenNonExclusions.has(args.path)) {
+          if (exclusions?.some((e) => e.startsWith(args.path))) {
+            // Similar to esbuild, --external:@foo/bar automatically implies --external:@foo/bar/*,
+            // which matches import paths like @foo/bar/baz.
+            // This means all paths within the @foo/bar package are also marked as external.
+            seenExclusion.add(args.path);
+
+            return null;
+          }
+
+          seenNonExclusions.add(args.path);
+        }
+
         const { importer, kind, resolveDir, namespace, pluginData = {} } = args;
         pluginData[EXTERNAL_PACKAGE_RESOLUTION] = true;