fix(ngcc): support element accesses for export declarations (#44669)

Bundlers like Rollup may use an element access expression for an export
declaration, which causes ngcc to ignore those export declarations possibly
resulting in incomplete processing of packages.

Element access syntax may be used when the declared name is not considered
as valid JS identifier, but bundlers may be conservative in determining whether
an identifier can be used (to emit a property access) and opt for a string
literal in an element access instead.

The element access syntax introduces a problem for ngcc, where it wouldn't
consider such export as class declaration, causing them to be skipped. The
ngtsc compiler is implemented with the assumption that all class declarations
use a `ts.Identifier` as name, whereas the element access is using a string
literal for the declared name. This makes it troublesome for ngcc to support
this syntax form in UMD bundles.

To work around the problem, this function transforms these access expressions
into regular property accesses. The source text is parsed to an AST to allow
finding the element accesses in a robust way, after which the affected text
ranges are replaced with property accesses in the original source text.

Closes #44037

PR Close #44669

packages/compiler-cli/ngcc/src/packages/adjust_cjs_umd_exports.ts

@@ -0,0 +1,82 @@
+/**
+ * @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 ts from 'typescript';
+
+/**
+ * UMD/CJS bundles generated by Rollup may be using an element access expression like
+ * `exports["ɵa"]` for declaring and exporting classes, instead of a property access like
+ * `exports.ɵa`. The element access syntax introduces a problem for ngcc, where it wouldn't consider
+ * such export as class declaration, causing them to be skipped. The ngtsc compiler is implemented
+ * with the assumption that all class declarations use a `ts.Identifier` as name, whereas the
+ * element access is using a string literal for the declared name. This makes it troublesome for
+ * ngcc to support this syntax form in UMD bundles.
+ *
+ * To work around the problem, this function transforms these access expressions into regular
+ * property accesses. The source text is parsed to an AST to allow finding the element accesses in a
+ * robust way, after which the affected text ranges are replaced with property accesses in the
+ * original source text. These replacement operations are faster than applying an AST transform and
+ * going through a `ts.Printer` to print the text back out.
+ */
+export function adjustElementAccessExports(sourceText: string): string {
+  // Do a quick check to avoid a full parse if the source cannot contain an element access
+  // expression. Note that this check results in a false negative if trivia (whitespace/comments) is
+  // present, but this should be good enough for our use-case.
+  if (!/exports\[["']/.test(sourceText)) {
+    return sourceText;
+  }
+
+  const replacements: {start: number; end: number; identifier: string}[] = [];
+
+  const sf = ts.createSourceFile(
+      'input.js', sourceText, ts.ScriptTarget.ES5, /* setParentNodes */ false, ts.ScriptKind.JS);
+  ts.forEachChild(sf, function visitNode(node: ts.Node) {
+    if (ts.isElementAccessExpression(node) && isExportsIdentifier(node.expression) &&
+        ts.isStringLiteral(node.argumentExpression) &&
+        isJsIdentifier(node.argumentExpression.text)) {
+      replacements.push({
+        start: node.getStart(sf),
+        end: node.getEnd(),
+        identifier: node.argumentExpression.text,
+      });
+    }
+    ts.forEachChild(node, visitNode);
+  });
+
+  // Sort the replacements in reverse order, such that applying the replacements does not invalidate
+  // the captured positions of other replacements.
+  replacements.sort((a, b) => a.start - b.start);
+
+  const parts: string[] = [];
+  let currentIndex = 0;
+  for (const replacement of replacements) {
+    parts.push(sourceText.substring(currentIndex, replacement.start));
+    // The whitespace is inserted such that the identifier aligns with the original string literal
+    // text, which means that source maps continue to be accurate.
+    parts.push(`exports. ${replacement.identifier}  `);
+    currentIndex = replacement.end;
+  }
+  parts.push(sourceText.substring(currentIndex));
+  return parts.join('');
+}
+
+function isExportsIdentifier(expr: ts.Expression): boolean {
+  return ts.isIdentifier(expr) && expr.text === 'exports';
+}
+
+/**
+ * An element access using a string literal can only be converted into a property access if the
+ * string is a valid JS identifier, i.e. not a reserved keyword.
+ *
+ * This regex is taken from {@link https://stackoverflow.com/a/9392578/171436}.
+ */
+const identifierPattern =
+    /^(?!(?:do|if|in|for|let|new|try|var|case|else|enum|eval|false|null|this|true|void|with|break|catch|class|const|super|throw|while|yield|delete|export|import|public|return|static|switch|typeof|default|extends|finally|package|private|continue|debugger|function|arguments|interface|protected|implements|instanceof)$)[$A-Z\_a-z\xaa\xb5\xba\xc0-\xd6\xd8-\xf6\xf8-\u02c1\u02c6-\u02d1\u02e0-\u02e4\u02ec\u02ee\u0370-\u0374\u0376\u0377\u037a-\u037d\u0386\u0388-\u038a\u038c\u038e-\u03a1\u03a3-\u03f5\u03f7-\u0481\u048a-\u0527\u0531-\u0556\u0559\u0561-\u0587\u05d0-\u05ea\u05f0-\u05f2\u0620-\u064a\u066e\u066f\u0671-\u06d3\u06d5\u06e5\u06e6\u06ee\u06ef\u06fa-\u06fc\u06ff\u0710\u0712-\u072f\u074d-\u07a5\u07b1\u07ca-\u07ea\u07f4\u07f5\u07fa\u0800-\u0815\u081a\u0824\u0828\u0840-\u0858\u08a0\u08a2-\u08ac\u0904-\u0939\u093d\u0950\u0958-\u0961\u0971-\u0977\u0979-\u097f\u0985-\u098c\u098f\u0990\u0993-\u09a8\u09aa-\u09b0\u09b2\u09b6-\u09b9\u09bd\u09ce\u09dc\u09dd\u09df-\u09e1\u09f0\u09f1\u0a05-\u0a0a\u0a0f\u0a10\u0a13-\u0a28\u0a2a-\u0a30\u0a32\u0a33\u0a35\u0a36\u0a38\u0a39\u0a59-\u0a5c\u0a5e\u0a72-\u0a74\u0a85-\u0a8d\u0a8f-\u0a91\u0a93-\u0aa8\u0aaa-\u0ab0\u0ab2\u0ab3\u0ab5-\u0ab9\u0abd\u0ad0\u0ae0\u0ae1\u0b05-\u0b0c\u0b0f\u0b10\u0b13-\u0b28\u0b2a-\u0b30\u0b32\u0b33\u0b35-\u0b39\u0b3d\u0b5c\u0b5d\u0b5f-\u0b61\u0b71\u0b83\u0b85-\u0b8a\u0b8e-\u0b90\u0b92-\u0b95\u0b99\u0b9a\u0b9c\u0b9e\u0b9f\u0ba3\u0ba4\u0ba8-\u0baa\u0bae-\u0bb9\u0bd0\u0c05-\u0c0c\u0c0e-\u0c10\u0c12-\u0c28\u0c2a-\u0c33\u0c35-\u0c39\u0c3d\u0c58\u0c59\u0c60\u0c61\u0c85-\u0c8c\u0c8e-\u0c90\u0c92-\u0ca8\u0caa-\u0cb3\u0cb5-\u0cb9\u0cbd\u0cde\u0ce0\u0ce1\u0cf1\u0cf2\u0d05-\u0d0c\u0d0e-\u0d10\u0d12-\u0d3a\u0d3d\u0d4e\u0d60\u0d61\u0d7a-\u0d7f\u0d85-\u0d96\u0d9a-\u0db1\u0db3-\u0dbb\u0dbd\u0dc0-\u0dc6\u0e01-\u0e30\u0e32\u0e33\u0e40-\u0e46\u0e81\u0e82\u0e84\u0e87\u0e88\u0e8a\u0e8d\u0e94-\u0e97\u0e99-\u0e9f\u0ea1-\u0ea3\u0ea5\u0ea7\u0eaa\u0eab\u0ead-\u0eb0\u0eb2\u0eb3\u0ebd\u0ec0-\u0ec4\u0ec6\u0edc-\u0edf\u0f00\u0f40-\u0f47\u0f49-\u0f6c\u0f88-\u0f8c\u1000-\u102a\u103f\u1050-\u1055\u105a-\u105d\u1061\u1065\u1066\u106e-\u1070\u1075-\u1081\u108e\u10a0-\u10c5\u10c7\u10cd\u10d0-\u10fa\u10fc-\u1248\u124a-\u124d\u1250-\u1256\u1258\u125a-\u125d\u1260-\u1288\u128a-\u128d\u1290-\u12b0\u12b2-\u12b5\u12b8-\u12be\u12c0\u12c2-\u12c5\u12c8-\u12d6\u12d8-\u1310\u1312-\u1315\u1318-\u135a\u1380-\u138f\u13a0-\u13f4\u1401-\u166c\u166f-\u167f\u1681-\u169a\u16a0-\u16ea\u16ee-\u16f0\u1700-\u170c\u170e-\u1711\u1720-\u1731\u1740-\u1751\u1760-\u176c\u176e-\u1770\u1780-\u17b3\u17d7\u17dc\u1820-\u1877\u1880-\u18a8\u18aa\u18b0-\u18f5\u1900-\u191c\u1950-\u196d\u1970-\u1974\u1980-\u19ab\u19c1-\u19c7\u1a00-\u1a16\u1a20-\u1a54\u1aa7\u1b05-\u1b33\u1b45-\u1b4b\u1b83-\u1ba0\u1bae\u1baf\u1bba-\u1be5\u1c00-\u1c23\u1c4d-\u1c4f\u1c5a-\u1c7d\u1ce9-\u1cec\u1cee-\u1cf1\u1cf5\u1cf6\u1d00-\u1dbf\u1e00-\u1f15\u1f18-\u1f1d\u1f20-\u1f45\u1f48-\u1f4d\u1f50-\u1f57\u1f59\u1f5b\u1f5d\u1f5f-\u1f7d\u1f80-\u1fb4\u1fb6-\u1fbc\u1fbe\u1fc2-\u1fc4\u1fc6-\u1fcc\u1fd0-\u1fd3\u1fd6-\u1fdb\u1fe0-\u1fec\u1ff2-\u1ff4\u1ff6-\u1ffc\u2071\u207f\u2090-\u209c\u2102\u2107\u210a-\u2113\u2115\u2119-\u211d\u2124\u2126\u2128\u212a-\u212d\u212f-\u2139\u213c-\u213f\u2145-\u2149\u214e\u2160-\u2188\u2c00-\u2c2e\u2c30-\u2c5e\u2c60-\u2ce4\u2ceb-\u2cee\u2cf2\u2cf3\u2d00-\u2d25\u2d27\u2d2d\u2d30-\u2d67\u2d6f\u2d80-\u2d96\u2da0-\u2da6\u2da8-\u2dae\u2db0-\u2db6\u2db8-\u2dbe\u2dc0-\u2dc6\u2dc8-\u2dce\u2dd0-\u2dd6\u2dd8-\u2dde\u2e2f\u3005-\u3007\u3021-\u3029\u3031-\u3035\u3038-\u303c\u3041-\u3096\u309d-\u309f\u30a1-\u30fa\u30fc-\u30ff\u3105-\u312d\u3131-\u318e\u31a0-\u31ba\u31f0-\u31ff\u3400-\u4db5\u4e00-\u9fcc\ua000-\ua48c\ua4d0-\ua4fd\ua500-\ua60c\ua610-\ua61f\ua62a\ua62b\ua640-\ua66e\ua67f-\ua697\ua6a0-\ua6ef\ua717-\ua71f\ua722-\ua788\ua78b-\ua78e\ua790-\ua793\ua7a0-\ua7aa\ua7f8-\ua801\ua803-\ua805\ua807-\ua80a\ua80c-\ua822\ua840-\ua873\ua882-\ua8b3\ua8f2-\ua8f7\ua8fb\ua90a-\ua925\ua930-\ua946\ua960-\ua97c\ua984-\ua9b2\ua9cf\uaa00-\uaa28\uaa40-\uaa42\uaa44-\uaa4b\uaa60-\uaa76\uaa7a\uaa80-\uaaaf\uaab1\uaab5\uaab6\uaab9-\uaabd\uaac0\uaac2\uaadb-\uaadd\uaae0-\uaaea\uaaf2-\uaaf4\uab01-\uab06\uab09-\uab0e\uab11-\uab16\uab20-\uab26\uab28-\uab2e\uabc0-\uabe2\uac00-\ud7a3\ud7b0-\ud7c6\ud7cb-\ud7fb\uf900-\ufa6d\ufa70-\ufad9\ufb00-\ufb06\ufb13-\ufb17\ufb1d\ufb1f-\ufb28\ufb2a-\ufb36\ufb38-\ufb3c\ufb3e\ufb40\ufb41\ufb43\ufb44\ufb46-\ufbb1\ufbd3-\ufd3d\ufd50-\ufd8f\ufd92-\ufdc7\ufdf0-\ufdfb\ufe70-\ufe74\ufe76-\ufefc\uff21-\uff3a\uff41-\uff5a\uff66-\uffbe\uffc2-\uffc7\uffca-\uffcf\uffd2-\uffd7\uffda-\uffdc][$A-Z\_a-z\xaa\xb5\xba\xc0-\xd6\xd8-\xf6\xf8-\u02c1\u02c6-\u02d1\u02e0-\u02e4\u02ec\u02ee\u0370-\u0374\u0376\u0377\u037a-\u037d\u0386\u0388-\u038a\u038c\u038e-\u03a1\u03a3-\u03f5\u03f7-\u0481\u048a-\u0527\u0531-\u0556\u0559\u0561-\u0587\u05d0-\u05ea\u05f0-\u05f2\u0620-\u064a\u066e\u066f\u0671-\u06d3\u06d5\u06e5\u06e6\u06ee\u06ef\u06fa-\u06fc\u06ff\u0710\u0712-\u072f\u074d-\u07a5\u07b1\u07ca-\u07ea\u07f4\u07f5\u07fa\u0800-\u0815\u081a\u0824\u0828\u0840-\u0858\u08a0\u08a2-\u08a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+
+function isJsIdentifier(text: string): boolean {
+  return identifierPattern.test(text);
+}

packages/compiler-cli/ngcc/src/packages/entry_point_bundle.ts

@@ -6,9 +6,12 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import ts from 'typescript';
+
 import {AbsoluteFsPath, FileSystem, ReadonlyFileSystem} from '../../../src/ngtsc/file_system';
 import {DtsProcessing} from '../execution/tasks/api';
 import {PathMappings} from '../path_mappings';
+
+import {adjustElementAccessExports} from './adjust_cjs_umd_exports';
 import {BundleProgram, makeBundleProgram} from './bundle_program';
 import {EntryPoint, EntryPointFormat} from './entry_point';
 import {NgccDtsCompilerHost, NgccSourcesCompilerHost} from './ngcc_compiler_host';
@@ -30,6 +33,20 @@ export interface EntryPointBundle {
   enableI18nLegacyMessageIdFormat: boolean;
 }
 
+/**
+ * When processing UMD or CommonJS bundles the source text is preprocessed to transform export
+ * declarations using element access expressions into property access expressions, as otherwise ngcc
+ * would not recognize these export declarations. See `adjustElementAccessExports` for more
+ * information.
+ */
+function createSourceTextProcessor(format: EntryPointFormat): (sourceText: string) => string {
+  if (format === 'umd' || format === 'commonjs') {
+    return adjustElementAccessExports;
+  } else {
+    return sourceText => sourceText;
+  }
+}
+
 /**
  * Get an object that describes a formatted bundle for an entry-point.
  * @param fs The current file-system being used.
@@ -56,7 +73,8 @@ export function makeEntryPointBundle(
   const rootDir = entryPoint.packagePath;
   const options: ts
       .CompilerOptions = {allowJs: true, maxNodeModuleJsDepth: Infinity, rootDir, ...pathMappings};
-  const entryPointCache = new EntryPointFileCache(fs, sharedFileCache);
+  const processSourceText = createSourceTextProcessor(format);
+  const entryPointCache = new EntryPointFileCache(fs, sharedFileCache, processSourceText);
   const dtsHost = new NgccDtsCompilerHost(fs, options, entryPointCache, moduleResolutionCache);
   const srcHost = new NgccSourcesCompilerHost(
       fs, options, entryPointCache, moduleResolutionCache, entryPoint.packagePath);

packages/compiler-cli/ngcc/src/packages/source_file_cache.ts

@@ -6,8 +6,11 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import ts from 'typescript';
+
 import {AbsoluteFsPath, ReadonlyFileSystem} from '../../../src/ngtsc/file_system';
 
+import {adjustElementAccessExports} from './adjust_cjs_umd_exports';
+
 /**
  * A cache that holds on to source files that can be shared for processing all entry-points in a
  * single invocation of ngcc. In particular, the following files are shared across all entry-points
@@ -147,7 +150,9 @@ function isFile(
 export class EntryPointFileCache {
   private readonly sfCache = new Map<AbsoluteFsPath, ts.SourceFile>();
 
-  constructor(private fs: ReadonlyFileSystem, private sharedFileCache: SharedFileCache) {}
+  constructor(
+      private fs: ReadonlyFileSystem, private sharedFileCache: SharedFileCache,
+      private processSourceText: (sourceText: string) => string) {}
 
   /**
    * Returns and caches a parsed `ts.SourceFile` for the provided `fileName`. If the `fileName` is
@@ -172,7 +177,8 @@ export class EntryPointFileCache {
     if (content === undefined) {
       return undefined;
     }
-    const sf = ts.createSourceFile(fileName, content, languageVersion);
+    const processed = this.processSourceText(content);
+    const sf = ts.createSourceFile(fileName, processed, languageVersion);
     this.sfCache.set(absPath, sf);
     return sf;
   }

packages/compiler-cli/ngcc/test/helpers/utils.ts

@@ -73,7 +73,8 @@ export function makeTestBundleProgram(
   const options: ts.CompilerOptions =
       {allowJs: true, maxNodeModuleJsDepth: Infinity, checkJs: false, rootDir, rootDirs: [rootDir]};
   const moduleResolutionCache = createModuleResolutionCache(fs);
-  const entryPointFileCache = new EntryPointFileCache(fs, new SharedFileCache(fs));
+  const entryPointFileCache =
+      new EntryPointFileCache(fs, new SharedFileCache(fs), sourceText => sourceText);
   const host =
       new NgccSourcesCompilerHost(fs, options, entryPointFileCache, moduleResolutionCache, rootDir);
   return makeBundleProgram(