fixup! fix(@angular/build): re-analyze exports on package.json change in library builder

Author: alan-agius4

packages/angular/build/src/builders/library/builder.ts

@@ -276,9 +276,10 @@ async function* runWatchLoop(
       try {
         const packageJson = await loadPackageJson(packageJsonPath);
         options.packageJson = packageJson;
-        if (packageJson.name) {
-          options.packageName = packageJson.name;
+        if (!packageJson.name) {
+          throw new Error(`The package.json at '${packageJsonPath}' must contain a 'name'.`);
         }
+        options.packageName = packageJson.name;
 
         updateWatchedEntryPoints(
           packageJson,

packages/angular/build/src/builders/library/pipeline/entry-points.ts

@@ -215,7 +215,7 @@ export function haveEntryPointsChanged(
 export function updateWatchedEntryPoints(
   packageJson: { exports?: unknown; name?: string },
   options: {
-    entryPoints: ReadonlyMap<string, NormalizedEntryPoint>;
+    entryPoints: Map<string, NormalizedEntryPoint>;
     projectRoot: string;
     packageName: string;
   },

packages/angular/build/src/builders/library/tests/behavior/watch_spec.ts

@@ -309,6 +309,36 @@ describeLibraryBuilder(executeLibraryBuilder, LIBRARY_BUILDER_INFO, (harness) =>
       ]);
     });
 
+    it('should fail with error when name is removed from package.json in watch mode', async () => {
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+        watch: true,
+      });
+
+      await harness.executeWithCases([
+        async ({ result }) => {
+          expect(result?.success).toBeTrue();
+
+          // Remove name from package.json
+          const pkg = JSON.parse(harness.readFile('projects/lib/package.json'));
+          delete pkg.name;
+          await harness.writeFile('projects/lib/package.json', JSON.stringify(pkg, null, 2));
+        },
+        async ({ result }) => {
+          expect(result?.success).toBeFalse();
+          expect(result?.error).toContain("must contain a 'name'");
+
+          // Restore name in package.json
+          const pkg = JSON.parse(harness.readFile('projects/lib/package.json'));
+          pkg.name = 'lib';
+          await harness.writeFile('projects/lib/package.json', JSON.stringify(pkg, null, 2));
+        },
+        async ({ result }) => {
+          expect(result?.success).toBeTrue();
+        },
+      ]);
+    });
+
     it('should recover from compilation errors in watch mode', async () => {
       await harness.writeFile(
         'projects/lib/src/public-api.ts',