angular-cli/packages/schematics/angular/migrations/update-12/update-lazy-module-paths.ts

/**
 * @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 { DirEntry, Rule, UpdateRecorder } from '@angular-devkit/schematics';
import * as ts from '../../third_party/github.com/Microsoft/TypeScript/lib/typescript';

function* visit(directory: DirEntry): IterableIterator<ts.SourceFile> {
  for (const path of directory.subfiles) {
    if (path.endsWith('.ts') && !path.endsWith('.d.ts')) {
      const entry = directory.file(path);
      if (entry) {
        const content = entry.content;
        if (content.includes('loadChildren')) {
          const source = ts.createSourceFile(
            entry.path,
            content.toString().replace(/^\uFEFF/, ''),
            ts.ScriptTarget.Latest,
            true,
          );

          yield source;
        }
      }
    }
  }

  for (const path of directory.subdirs) {
    if (path === 'node_modules' || path.startsWith('.')) {
      continue;
    }

    yield* visit(directory.dir(path));
  }
}

export default function (): Rule {
  return (tree) => {
    for (const sourceFile of visit(tree.root)) {
      let recorder: UpdateRecorder | undefined;

      ts.forEachChild(sourceFile, function analyze(node) {
        if (
          ts.isPropertyAssignment(node) &&
          (ts.isIdentifier(node.name) || ts.isStringLiteral(node.name)) &&
          node.name.text === 'loadChildren' &&
          ts.isStringLiteral(node.initializer)
        ) {
          const valueNode = node.initializer;
          const parts = valueNode.text.split('#');
          const path = parts[0];
          const moduleName = parts[1] || 'default';

          const fix = `() => import('${path}').then(m => m.${moduleName})`;

          if (!recorder) {
            recorder = tree.beginUpdate(sourceFile.fileName);
          }

          const index = valueNode.getStart();
          const length = valueNode.getWidth();
          recorder.remove(index, length).insertLeft(index, fix);
        }

        ts.forEachChild(node, analyze);
      });

      if (recorder) {
        tree.commitUpdate(recorder);
      }
    }
  };
}