feat(@angular-devkit/architect): add implementation for defaultConfiguration

With this change, the architect can be configured to use a default configuration when it's not provided as part of the target.

Consider the below, where `defaultConfiguration` is configured to `production`. Running `ng build` will be invoked with "production" configuration.

```js
"build": {
  "builder": "@angular-devkit/build-angular:browser",
  "defaultConfiguration": "production",
  "options": {
      ...
  },
  "configurations": {
    "production": {
        ...
    }
  }
}
```

Author: alan-agius4

packages/angular_devkit/architect/node/node-modules-architect-host.ts

@@ -30,6 +30,7 @@ export interface WorkspaceHost {
   getMetadata(project: string): Promise<json.JsonObject>;
   getOptions(project: string, target: string, configuration?: string): Promise<json.JsonObject>;
   hasTarget(project: string, target: string): Promise<boolean>;
+  getDefaultConfigurationName(project: string, target: string): Promise<string | undefined>;
 }
 
 function findProjectTarget(
@@ -99,6 +100,9 @@ export class WorkspaceNodeModulesArchitectHost implements ArchitectHost<NodeModu
         async hasTarget(project, target) {
           return !!workspaceOrHost.projects.get(project)?.targets.has(target);
         },
+        async getDefaultConfigurationName(project, target) {
+          return workspaceOrHost.projects.get(project)?.targets.get(target)?.defaultConfiguration;
+        },
       };
     }
   }
@@ -166,9 +170,11 @@ export class WorkspaceNodeModulesArchitectHost implements ArchitectHost<NodeModu
     }
 
     let options = await this.workspaceHost.getOptions(target.project, target.target);
+    const targetConfiguration =
+      target.configuration || await this.workspaceHost.getDefaultConfigurationName(target.project, target.target);
 
-    if (target.configuration) {
-      const configurations = target.configuration.split(',').map((c) => c.trim());
+    if (targetConfiguration) {
+      const configurations = targetConfiguration.split(',').map((c) => c.trim());
       for (const configuration of configurations) {
         options = {
           ...options,

packages/angular_devkit/build_angular/src/testing/builder-harness.ts

@@ -174,6 +174,9 @@ export class BuilderHarness<T> {
 
         return this.targetName === target || this.builderTargets.has(target);
       },
+      getDefaultConfigurationName: async (_project, _target) => {
+        return undefined;
+      },
       validate: async (options, builderName) => {
         let schema;
         if (builderName === this.builderInfo.builderName) {

tests/legacy-cli/e2e/tests/misc/target-default-configuration.ts

@@ -0,0 +1,35 @@
+import { expectFileToExist } from '../../utils/fs';
+import { ng } from '../../utils/process';
+import { updateJsonFile } from '../../utils/project';
+import { expectToFail } from '../../utils/utils';
+
+export default async function () {
+  await updateJsonFile('angular.json', workspace => {
+    const build = workspace.projects['test-project'].architect.build;
+    build.defaultConfiguration = undefined;
+    build.options = {
+      ...build.options,
+      optimization: false,
+      buildOptimizer: false,
+      outputHashing: 'none',
+      sourceMap: true,
+    };
+  });
+
+  await ng('build');
+  await expectFileToExist('dist/test-project/main.js');
+  await expectFileToExist('dist/test-project/main.js.map');
+
+  // Add new configuration and set "defaultConfiguration"
+  await updateJsonFile('angular.json', workspace => {
+    const build = workspace.projects['test-project'].architect.build;
+    build.defaultConfiguration = 'defaultConfiguration';
+    build.configurations.defaultConfiguration = {
+      sourceMap: false,
+    };
+  });
+
+  await ng('build');
+  await expectFileToExist('dist/test-project/main.js');
+  await expectToFail(() => expectFileToExist('dist/test-project/main.js.map'));
+}