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/utils/line_mappings.ts

@@ -0,0 +1,63 @@
+/**
+ * @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
+ */
+
+const LF_CHAR = 10;
+const CR_CHAR = 13;
+const LINE_SEP_CHAR = 8232;
+const PARAGRAPH_CHAR = 8233;
+
+/** Gets the line and character for the given position from the line starts map. */
+export function getLineAndCharacterFromPosition(lineStartsMap: number[], position: number) {
+  const lineIndex = findClosestLineStartPosition(lineStartsMap, position);
+  return {character: position - lineStartsMap[lineIndex], line: lineIndex};
+}
+
+/**
+ * Computes the line start map of the given text. This can be used in order to
+ * retrieve the line and character of a given text position index.
+ */
+export function computeLineStartsMap(text: string): number[] {
+  const result: number[] = [0];
+  let pos = 0;
+  while (pos < text.length) {
+    const char = text.charCodeAt(pos++);
+    // Handles the "CRLF" line break. In that case we peek the character
+    // after the "CR" and check if it is a line feed.
+    if (char === CR_CHAR) {
+      if (text.charCodeAt(pos) === LF_CHAR) {
+        pos++;
+      }
+      result.push(pos);
+    } else if (char === LF_CHAR || char === LINE_SEP_CHAR || char === PARAGRAPH_CHAR) {
+      result.push(pos);
+    }
+  }
+  result.push(pos);
+  return result;
+}
+
+/** Finds the closest line start for the given position. */
+function findClosestLineStartPosition<T>(
+    linesMap: T[], position: T, low = 0, high = linesMap.length - 1) {
+  while (low <= high) {
+    const pivotIdx = Math.floor((low + high) / 2);
+    const pivotEl = linesMap[pivotIdx];
+
+    if (pivotEl === position) {
+      return pivotIdx;
+    } else if (position > pivotEl) {
+      low = pivotIdx + 1;
+    } else {
+      high = pivotIdx - 1;
+    }
+  }
+
+  // In case there was no exact match, return the closest "lower" line index. We also
+  // subtract the index by one because want the index of the previous line start.
+  return low - 1;
+}

packages/core/schematics/utils/ng_decorators.ts

@@ -11,7 +11,7 @@ import {getCallDecoratorImport} from './typescript/decorators';
 
 export type CallExpressionDecorator = ts.Decorator & {
   expression: ts.CallExpression;
-}
+};
 
 export interface NgDecorator {
   name: string;

packages/core/schematics/utils/tslint/BUILD.bazel

@@ -0,0 +1,8 @@
+load("//tools:defaults.bzl", "ts_library")
+
+ts_library(
+    name = "tslint",
+    srcs = glob(["**/*.ts"]),
+    tsconfig = "//packages/core/schematics:tsconfig.json",
+    visibility = ["//packages/core/schematics/migrations/template-var-assignment/google3:__pkg__"],
+)

packages/core/schematics/utils/tslint/tslint_html_source_file.ts

@@ -0,0 +1,37 @@
+/**
+ * @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 * as ts from 'typescript';
+
+/**
+ * Creates a fake TypeScript source file that can contain content of templates or stylesheets.
+ * The fake TypeScript source file then can be passed to TSLint in combination with a rule failure.
+ */
+export function createHtmlSourceFile(filePath: string, content: string): ts.SourceFile {
+  const sourceFile = ts.createSourceFile(filePath, `\`${content}\``, ts.ScriptTarget.ES5);
+
+  // Subtract two characters because the string literal quotes are only needed for parsing
+  // and are not part of the actual source file.
+  sourceFile.end = sourceFile.end - 2;
+
+  // Note: This does not affect the way TSLint applies replacements for external resource files.
+  // At the time of writing, TSLint loads files manually if the actual rule source file is not
+  // equal to the source file of the replacement. This means that the replacements need proper
+  // offsets without the string literal quote symbols.
+  sourceFile.getFullText = function() {
+    return sourceFile.text.substring(1, sourceFile.text.length - 1);
+  };
+
+  sourceFile.getText = sourceFile.getFullText;
+
+  // Update the "text" property to be set to the template content without quotes. This is
+  // necessary so that the TypeScript line starts map is properly computed.
+  sourceFile.text = sourceFile.getFullText();
+
+  return sourceFile;
+}