feat(core): template-var-assignment update schematic (#29608)

Introduces a new update schematic called "template-var-assignment"
that is responsible for analyzing template files in order to warn
developers if template variables are assigned to values.

The schematic also comes with a driver for `tslint` so that the
check can be used wtihin Google.

PR Close #29608

packages/core/schematics/test/google3/no_template_variable_assignment_rule_spec.ts

@@ -0,0 +1,110 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {writeFileSync} from 'fs';
+import {dirname, join} from 'path';
+import * as shx from 'shelljs';
+import {Configuration, Linter} from 'tslint';
+
+describe('Google3 noTemplateVariableAssignment TSLint rule', () => {
+  const rulesDirectory = dirname(require.resolve(
+      '../../migrations/template-var-assignment/google3/noTemplateVariableAssignmentRule'));
+
+  let tmpDir: string;
+
+  beforeEach(() => {
+    tmpDir = join(process.env['TEST_TMPDIR'] !, 'google3-test');
+    shx.mkdir('-p', tmpDir);
+
+    writeFile('tsconfig.json', JSON.stringify({compilerOptions: {module: 'es2015'}}));
+  });
+
+  afterEach(() => shx.rm('-r', tmpDir));
+
+  /** Runs TSLint with the no-template-variable TSLint rule.*/
+  function runTSLint() {
+    const program = Linter.createProgram(join(tmpDir, 'tsconfig.json'));
+    const linter = new Linter({fix: false, rulesDirectory: [rulesDirectory]}, program);
+    const config = Configuration.parseConfigFile(
+        {rules: {'no-template-variable-assignment': true}, linterOptions: {typeCheck: true}});
+
+    program.getRootFileNames().forEach(fileName => {
+      linter.lint(fileName, program.getSourceFile(fileName) !.getFullText(), config);
+    });
+
+    return linter;
+  }
+
+  /** Writes a file to the current temporary directory. */
+  function writeFile(fileName: string, content: string) {
+    writeFileSync(join(tmpDir, fileName), content);
+  }
+
+  it('should create failure for detected two-way data binding assignment', () => {
+    writeFile('index.ts', `
+      import {Component} from '@angular/core';
+      
+      @Component({template: '<span *ngFor="let i of options" [(a)]="i"></span>'})
+      export class MyComp {}
+    `);
+
+    const linter = runTSLint();
+    const failures = linter.getResult().failures;
+
+    expect(failures.length).toBe(1);
+    expect(failures[0].getFileName()).toContain('index.ts');
+    expect(failures[0].getStartPosition().getLineAndCharacter()).toEqual({line: 3, character: 68});
+    expect(failures[0].getEndPosition().getLineAndCharacter()).toEqual({line: 3, character: 69});
+    expect(failures[0].getFailure()).toMatch(/^Found assignment to template variable./);
+  });
+
+  it('should create failure with correct offsets for external templates', () => {
+    writeFile('index.ts', `
+      import {Component} from '@angular/core';
+      
+      @Component({templateUrl: './my-tmpl.html'})
+      export class MyComp {}
+    `);
+
+    writeFile(`my-tmpl.html`, `
+      <span *ngFor="let option of options" [(a)]="option"></span>
+    `);
+
+    const linter = runTSLint();
+    const failures = linter.getResult().failures;
+
+    expect(failures.length).toBe(1);
+    expect(failures[0].getFileName()).toContain('my-tmpl.html');
+    expect(failures[0].getStartPosition().getLineAndCharacter()).toEqual({line: 1, character: 50});
+    expect(failures[0].getEndPosition().getLineAndCharacter()).toEqual({line: 1, character: 56});
+    expect(failures[0].getFailure()).toMatch(/^Found assignment to template variable./);
+  });
+
+  it('should create failure for template variable assignment within output', () => {
+    writeFile('index.ts', `
+      import {Component} from '@angular/core';
+      
+      @Component({templateUrl: './my-tmpl.html'})
+      export class MyComp {}
+    `);
+
+    writeFile(`my-tmpl.html`, `
+      <!-- Comment -->
+      <span *ngFor="let option of options" (click)="option = true"></span>
+    `);
+
+    const linter = runTSLint();
+    const failures = linter.getResult().failures;
+
+    expect(failures.length).toBe(1);
+    expect(failures[0].getFileName()).toContain('my-tmpl.html');
+    expect(failures[0].getStartPosition().getLineAndCharacter()).toEqual({line: 2, character: 52});
+    expect(failures[0].getEndPosition().getLineAndCharacter()).toEqual({line: 2, character: 65});
+    expect(failures[0].getFailure()).toMatch(/^Found assignment to template variable./);
+  });
+});