fix(bazel): do not modify tsconfig.json (#30877)

Before this change, user's tsconfig.json is cloned and some options
controlled by Bazel are removed otherwise Bazel would complain about:

```
WARNING: your tsconfig.json file specifies options which are overridden by Bazel:
 - compilerOptions.target and compilerOptions.module are controlled by downstream dependencies, such as ts_devserver
 - compilerOptions.typeRoots is always set to the @types subdirectory of the node_modules attribute
 - compilerOptions.rootDir and compilerOptions.baseUrl are always the workspace root directory
```

Since the warning has been removed in rules_typescript/8d8d398, there's no
need to clone and backup tsconfig.json

PR Close #30877

aio/content/guide/bazel.md

@@ -45,7 +45,6 @@ Outputs from Bazel appear in the `dist/bin` folder.
 If you need to opt-out from using Bazel, you can restore the backup files:
 
 - `/angular.json.bak` replaces `/angular.json`
-- `/tsconfig.json.bak` replaces `/tsconfig.json`
 
 ## Advanced configuration
 

integration/bazel-schematics/test.sh

@@ -41,7 +41,6 @@ function testBazel() {
 function testNonBazel() {
   # Replace angular.json that uses Bazel builder with the default generated by CLI
   mv ./angular.json.bak ./angular.json
-  mv ./tsconfig.json.bak ./tsconfig.json
   rm -rf dist src/main.dev.ts src/main.prod.ts
   yarn webdriver-manager update --gecko=false --standalone=false ${CI_CHROMEDRIVER_VERSION_ARG:---versions.chrome 2.45}
   ng build --progress=false

packages/bazel/src/schematics/ng-add/index.ts

@@ -222,65 +222,6 @@ function backupAngularJson(): Rule {
   };
 }
 
-/**
- * Create a backup for the original tsconfig.json file in case user wants to
- * eject Bazel and revert to the original workflow.
- */
-function backupTsconfigJson(): Rule {
-  return (host: Tree, context: SchematicContext) => {
-    const tsconfigPath = 'tsconfig.json';
-    if (!host.exists(tsconfigPath)) {
-      return;
-    }
-    host.create(
-        `${tsconfigPath}.bak`, '// This is a backup file of the original tsconfig.json. ' +
-            'This file is needed in case you want to revert to the workflow without Bazel.\n\n' +
-            host.read(tsconfigPath));
-  };
-}
-
-/**
- * Bazel controls the compilation options of tsc, so many options in
- * tsconfig.json generated by the default CLI schematics are not applicable.
- * This function updates the tsconfig.json to remove Bazel-controlled
- * parameters. This prevents Bazel from printing out warnings about overriden
- * settings.
- */
-function updateTsconfigJson(): Rule {
-  return (host: Tree, context: SchematicContext) => {
-    const tsconfigPath = 'tsconfig.json';
-    if (!host.exists(tsconfigPath)) {
-      return host;
-    }
-    const contentRaw = host.read(tsconfigPath) !.toString();
-    if (!contentRaw) {
-      return host;
-    }
-    const content = contentRaw.toString();
-    const ast = parseJsonAst(content);
-    if (!isJsonAstObject(ast)) {
-      return host;
-    }
-    const compilerOptions = findPropertyInAstObject(ast, 'compilerOptions');
-    if (!isJsonAstObject(compilerOptions)) {
-      return host;
-    }
-    const recorder = host.beginUpdate(tsconfigPath);
-    // target and module are controlled by downstream dependencies, such as
-    // ts_devserver
-    removeKeyValueInAstObject(recorder, content, compilerOptions, 'target');
-    removeKeyValueInAstObject(recorder, content, compilerOptions, 'module');
-    // typeRoots is always set to the @types subdirectory of the node_modules
-    // attribute
-    removeKeyValueInAstObject(recorder, content, compilerOptions, 'typeRoots');
-    // rootDir and baseUrl are always the workspace root directory
-    removeKeyValueInAstObject(recorder, content, compilerOptions, 'rootDir');
-    removeKeyValueInAstObject(recorder, content, compilerOptions, 'baseUrl');
-    host.commitUpdate(recorder);
-    return host;
-  };
-}
-
 /**
  * @angular/bazel requires minimum version of rxjs to be 6.4.0. This function
  * upgrades the version of rxjs in package.json if necessary.
@@ -388,10 +329,8 @@ export default function(options: Schema): Rule {
       addDevDependenciesToPackageJson(options),
       addPostinstallToGenerateNgSummaries(),
       backupAngularJson(),
-      backupTsconfigJson(),
       updateAngularJsonToUseBazelBuilder(options),
       updateGitignore(),
-      updateTsconfigJson(),
       upgradeRxjs(),
       installNodeModules(options),
     ]);

packages/bazel/src/schematics/ng-add/index_spec.ts

@@ -228,29 +228,6 @@ describe('ng-add schematic', () => {
     expect(builder).toBe('@angular/bazel:build');
   });
 
-  it('should create a backup for original tsconfig.json', async() => {
-    expect(host.files).toContain('/tsconfig.json');
-    const original = host.readContent('/tsconfig.json');
-    host = await schematicRunner.runSchematicAsync('ng-add', defaultOptions, host).toPromise();
-    expect(host.files).toContain('/tsconfig.json.bak');
-    const content = host.readContent('/tsconfig.json.bak');
-    expect(content.startsWith('// This is a backup file')).toBe(true);
-    expect(content).toMatch(original);
-  });
-
-  it('should remove Bazel-controlled options from tsconfig.json', async() => {
-    host = await schematicRunner.runSchematicAsync('ng-add', defaultOptions, host).toPromise();
-    expect(host.files).toContain('/tsconfig.json');
-    const content = host.readContent('/tsconfig.json');
-    expect(() => JSON.parse(content)).not.toThrow();
-    expect(JSON.parse(content)).toEqual({
-      compileOnSave: false,
-      compilerOptions: {
-        outDir: './dist/out-tsc',
-      }
-    });
-  });
-
   describe('rxjs', () => {
     const cases = [
       // version|upgrade