refactor(@angular/build): provide a default for the ng-packagr project option

goldens/public-api/angular/build/index.api.md

@@ -166,7 +166,7 @@ export type ExtractI18nBuilderOptions = {
 // @public
 export type NgPackagrBuilderOptions = {
     poll?: number;
-    project: string;
+    project?: string;
     tsConfig?: string;
     watch?: boolean;
 };

packages/angular/build/src/builders/ng-packagr/builder.ts

@@ -30,7 +30,7 @@ export async function* execute(
   // Purge old build disk cache.
   await purgeStaleBuildCache(context);
 
-  const root = context.workspaceRoot;
+  const workspaceRoot = context.workspaceRoot;
   let packager;
   try {
     packager = (await import('ng-packagr')).ngPackagr();
@@ -47,18 +47,22 @@ export async function* execute(
     throw error;
   }
 
-  packager.forProject(resolve(root, options.project));
-
-  if (options.tsConfig) {
-    packager.withTsConfig(resolve(root, options.tsConfig));
-  }
-
   const projectName = context.target?.project;
   if (!projectName) {
     throw new Error('The builder requires a target.');
   }
 
   const metadata = await context.getProjectMetadata(projectName);
+  const ngPackagrConfig = options.project
+    ? join(workspaceRoot, options.project)
+    : join(workspaceRoot, (metadata.root as string | undefined) ?? '', 'ng-package.json');
+
+  packager.forProject(ngPackagrConfig);
+
+  if (options.tsConfig) {
+    packager.withTsConfig(resolve(workspaceRoot, options.tsConfig));
+  }
+
   const { enabled: cacheEnabled, path: cacheDirectory } = normalizeCacheOptions(
     metadata,
     context.workspaceRoot,

packages/angular/build/src/builders/ng-packagr/schema.json

@@ -22,6 +22,5 @@
       "description": "Enable and define the file watching poll time period in milliseconds."
     }
   },
-  "additionalProperties": false,
-  "required": ["project"]
+  "additionalProperties": false
 }

packages/schematics/angular/library/index.ts

@@ -93,9 +93,6 @@ function addLibToWorkspaceFile(
         build: {
           builder: Builders.BuildNgPackagr,
           defaultConfiguration: 'production',
-          options: {
-            project: `${projectRoot}/ng-package.json`,
-          },
           configurations: {
             production: {
               tsConfig: `${projectRoot}/tsconfig.lib.prod.json`,

packages/schematics/angular/library/index_spec.ts

@@ -361,7 +361,6 @@ describe('Library Schematic', () => {
     const project = config.projects.foo;
     expect(project.root).toEqual('foo');
     const { options, configurations } = project.architect.build;
-    expect(options.project).toEqual('foo/ng-package.json');
     expect(configurations.production.tsConfig).toEqual('foo/tsconfig.lib.prod.json');
 
     const libTsConfig = getJsonFileContent(tree, '/foo/tsconfig.lib.json');