refactor(@angular/build): make buildTarget optional in unit-test builder

The `buildTarget` option in the `unit-test` builder is now optional to streamline the user configuration.

If the `buildTarget` option is not provided, the builder now defaults to using the `build` target with the `development` configuration for the current project. This change significantly reduces the boilerplate configuration needed in `angular.json` for most projects, as the builder can now infer the correct build settings by convention.

The builder's schema has been updated to reflect this change by removing `buildTarget` from the required properties and updating its description to document the new default behavior.

Author: clydin

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

@@ -216,7 +216,7 @@ export type NgPackagrBuilderOptions = {
 // @public
 export type UnitTestBuilderOptions = {
     browsers?: string[];
-    buildTarget: string;
+    buildTarget?: string;
     coverage?: boolean;
     coverageAll?: boolean;
     coverageExclude?: string[];

packages/angular/build/src/builders/unit-test/builder.ts

@@ -240,9 +240,22 @@ export async function* execute(
   // Get base build options from the buildTarget
   let buildTargetOptions: ApplicationBuilderInternalOptions;
   try {
+    const builderName = await context.getBuilderNameForTarget(normalizedOptions.buildTarget);
+    if (
+      builderName !== '@angular/build:application' &&
+      // TODO: Add comprehensive support for ng-packagr.
+      builderName !== '@angular/build:ng-packagr'
+    ) {
+      context.logger.warn(
+        `The 'buildTarget' is configured to use '${builderName}', which is not supported. ` +
+          `The 'unit-test' builder is designed to work with '@angular/build:application'. ` +
+          'Unexpected behavior or build failures may occur.',
+      );
+    }
+
     buildTargetOptions = (await context.validateOptions(
       await context.getTargetOptions(normalizedOptions.buildTarget),
-      await context.getBuilderNameForTarget(normalizedOptions.buildTarget),
+      builderName,
     )) as unknown as ApplicationBuilderInternalOptions;
   } catch (e) {
     assertIsError(e);
@@ -297,12 +310,9 @@ export async function* execute(
       ...runnerBuildOptions,
       watch: normalizedOptions.watch,
       progress: normalizedOptions.buildProgress ?? buildTargetOptions.progress,
+      ...(normalizedOptions.tsConfig ? { tsConfig: normalizedOptions.tsConfig } : {}),
     } satisfies ApplicationBuilderInternalOptions;
 
-    if (normalizedOptions.tsConfig) {
-      applicationBuildOptions.tsConfig = normalizedOptions.tsConfig;
-    }
-
     const dumpDirectory = normalizedOptions.dumpVirtualFiles
       ? path.join(normalizedOptions.cacheOptions.path, 'unit-test', 'output-files')
       : undefined;

packages/angular/build/src/builders/unit-test/schema.json

@@ -6,7 +6,7 @@
   "properties": {
     "buildTarget": {
       "type": "string",
-      "description": "Specifies the build target to use for the unit test build in the format `project:target[:configuration]`. You can also pass a comma-separated list of configurations. Example: `project:target:production,staging`.",
+      "description": "Specifies the build target to use for the unit test build in the format `project:target[:configuration]`. This defaults to the `build` target of the current project with the `development` configuration. You can also pass a comma-separated list of configurations. Example: `project:target:production,staging`.",
       "pattern": "^[^:\\s]*:[^:\\s]*(:[^\\s]+)?$"
     },
     "tsConfig": {
@@ -262,5 +262,5 @@
     }
   },
   "additionalProperties": false,
-  "required": ["buildTarget", "runner"]
+  "required": ["runner"]
 }