feat(material/schematics): tree operation helper functions (#24539)

* feat(material/schematics): tree operation helper functions

* created tree-traversal.ts for storing tree operation helper fns
* moved visitElements to the new file
* created helper fns for parseTemplate, and tag name changes
* added unit tests which don't need to call the whole schematic

Author: wagnermaciel

src/material/schematics/ng-generate/mdc-migration/BUILD.bazel

@@ -57,6 +57,7 @@ ts_library(
         "//src/cdk/schematics/testing",
         "@npm//@angular-devkit/core",
         "@npm//@angular-devkit/schematics",
+        "@npm//@angular/compiler",
         "@npm//@bazel/runfiles",
         "@npm//@types/jasmine",
         "@npm//@types/node",

src/material/schematics/ng-generate/mdc-migration/rules/template-migration.ts

@@ -9,43 +9,13 @@
 import {Migration, ResolvedResource} from '@angular/cdk/schematics';
 import {SchematicContext} from '@angular-devkit/schematics';
 import {StyleMigrator} from './style-migrator';
-import * as compiler from '@angular/compiler';
-
-/**
- * Traverses the given tree of nodes and runs the given callbacks for each Element node encountered.
- *
- * Note that updates to the start tags of html element should be done in the postorder callback,
- * and updates to the end tags of html elements should be done in the preorder callback to avoid
- * issues with line collisions.
- *
- * @param nodes The nodes of the ast from a parsed template.
- * @param preorderCallback A function that gets run for each Element node in a preorder traversal.
- * @param postorderCallback A function that gets run for each Element node in a postorder traversal.
- */
-function visitElements(
-  nodes: compiler.TmplAstNode[],
-  preorderCallback: (node: compiler.TmplAstElement) => void = () => {},
-  postorderCallback: (node: compiler.TmplAstElement) => void = () => {},
-): void {
-  for (let i = 0; i < nodes.length; i++) {
-    const node = nodes[i];
-    if (node instanceof compiler.TmplAstElement) {
-      preorderCallback(node);
-      visitElements(node.children, preorderCallback, postorderCallback);
-      postorderCallback(node);
-    }
-  }
-}
+import {visitElements, parseTemplate} from './tree-traversal';
 
 export class TemplateMigration extends Migration<StyleMigrator[], SchematicContext> {
   enabled = true;
 
   override visitTemplate(template: ResolvedResource) {
-    const ast = compiler.parseTemplate(template.content, template.filePath, {
-      preserveWhitespaces: true,
-      preserveLineEndings: true,
-      leadingTriviaChars: [],
-    });
+    const ast = parseTemplate(template.content, template.filePath);
 
     visitElements(ast.nodes, node => {
       // TODO(wagnermaciel): implement the migration updates.

src/material/schematics/ng-generate/mdc-migration/rules/tree-traversal.spec.ts

@@ -0,0 +1,79 @@
+import {visitElements, parseTemplate, replaceStartTag, replaceEndTag} from './tree-traversal';
+
+function runTagNameDuplicationTest(html: string, result: string): void {
+  visitElements(
+    parseTemplate(html).nodes,
+    node => {
+      html = replaceEndTag(html, node, node.name.repeat(2));
+    },
+    node => {
+      html = replaceStartTag(html, node, node.name.repeat(2));
+    },
+  );
+  expect(html).toBe(result);
+}
+
+describe('#visitElements', () => {
+  describe('tag name replacements', () => {
+    it('should handle basic cases', async () => {
+      runTagNameDuplicationTest('<a></a>', '<aa></aa>');
+    });
+
+    it('should handle multiple same line', async () => {
+      runTagNameDuplicationTest('<a></a><b></b>', '<aa></aa><bb></bb>');
+    });
+
+    it('should handle multiple same line nested', async () => {
+      runTagNameDuplicationTest('<a><b></b></a>', '<aa><bb></bb></aa>');
+    });
+
+    it('should handle multiple same line nested and unnested', async () => {
+      runTagNameDuplicationTest('<a><b></b><c></c></a>', '<aa><bb></bb><cc></cc></aa>');
+    });
+
+    it('should handle multiple multi-line', async () => {
+      runTagNameDuplicationTest(
+        `
+          <a></a>
+          <b></b>
+        `,
+        `
+          <aa></aa>
+          <bb></bb>
+        `,
+      );
+    });
+
+    it('should handle multiple multi-line nested', async () => {
+      runTagNameDuplicationTest(
+        `
+          <a>
+            <b></b>
+          </a>
+        `,
+        `
+          <aa>
+            <bb></bb>
+          </aa>
+        `,
+      );
+    });
+
+    it('should handle multiple multi-line nested and unnested', async () => {
+      runTagNameDuplicationTest(
+        `
+          <a>
+            <b></b>
+            <c></c>
+          </a>
+        `,
+        `
+          <aa>
+            <bb></bb>
+            <cc></cc>
+          </aa>
+        `,
+      );
+    });
+  });
+});

src/material/schematics/ng-generate/mdc-migration/rules/tree-traversal.ts

@@ -0,0 +1,97 @@
+/**
+ * @license
+ * Copyright Google LLC 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 compiler from '@angular/compiler';
+
+/**
+ * Traverses the given tree of nodes and runs the given callbacks for each Element node encountered.
+ *
+ * Note that updates to the start tags of html element should be done in the postorder callback,
+ * and updates to the end tags of html elements should be done in the preorder callback to avoid
+ * issues with line collisions.
+ *
+ * @param nodes The nodes of the ast from a parsed template.
+ * @param preorderCallback A function that gets run for each Element node in a preorder traversal.
+ * @param postorderCallback A function that gets run for each Element node in a postorder traversal.
+ */
+export function visitElements(
+  nodes: compiler.TmplAstNode[],
+  preorderCallback: (node: compiler.TmplAstElement) => void = () => {},
+  postorderCallback: (node: compiler.TmplAstElement) => void = () => {},
+): void {
+  nodes.reverse();
+  for (let i = 0; i < nodes.length; i++) {
+    const node = nodes[i];
+    if (node instanceof compiler.TmplAstElement) {
+      preorderCallback(node);
+      visitElements(node.children, preorderCallback, postorderCallback);
+      postorderCallback(node);
+    }
+  }
+}
+
+/**
+ * A wrapper for the Angular compilers parseTemplate, which passes the correct options to ensure
+ * the parsed template is accurate.
+ *
+ * For more details, see https://github.com/angular/angular/blob/4332897baa2226ef246ee054fdd5254e3c129109/packages/compiler-cli/src/ngtsc/annotations/component/src/resources.ts#L230.
+ *
+ * @param html text of the template to parse
+ * @param filePath URL to use for source mapping of the parsed template
+ * @returns the updated template html.
+ */
+export function parseTemplate(template: string, templateUrl: string = ''): compiler.ParsedTemplate {
+  return compiler.parseTemplate(template, templateUrl, {
+    preserveWhitespaces: true,
+    preserveLineEndings: true,
+    leadingTriviaChars: [],
+  });
+}
+
+/**
+ * Replaces the start tag of the given Element node inside of the html document with a new tag name.
+ *
+ * @param html The full html document.
+ * @param node The Element node to be updated.
+ * @param tag A new tag name.
+ * @returns an updated html document.
+ */
+export function replaceStartTag(html: string, node: compiler.TmplAstElement, tag: string): string {
+  return replaceAt(html, node.startSourceSpan.start.offset + 1, node.name, tag);
+}
+
+/**
+ * Replaces the end tag of the given Element node inside of the html document with a new tag name.
+ *
+ * @param html The full html document.
+ * @param node The Element node to be updated.
+ * @param tag A new tag name.
+ * @returns an updated html document.
+ */
+export function replaceEndTag(html: string, node: compiler.TmplAstElement, tag: string): string {
+  if (!node.endSourceSpan) {
+    return html;
+  }
+  return replaceAt(html, node.endSourceSpan.start.offset + 2, node.name, tag);
+}
+
+/**
+ * Replaces a substring of a given string starting at some offset index.
+ *
+ * @param str A string to be updated.
+ * @param offset An offset index to start at.
+ * @param oldSubstr The old substring to be replaced.
+ * @param newSubstr A new substring.
+ * @returns the updated string.
+ */
+function replaceAt(str: string, offset: number, oldSubstr: string, newSubstr: string): string {
+  const index = offset;
+  const prefix = str.slice(0, index);
+  const suffix = str.slice(index + oldSubstr.length);
+  return prefix + newSubstr + suffix;
+}