Polyfill string.matchAll to unblock #7770 (#7776)

Manually write a polyfill for string.matchAll to unblock #7770. This should be replaced with core-js in the future.

Author: mattsoulanille

tfjs-layers/src/layers/nlp/match_all_polyfill.ts

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+/**
+ * @license
+ * Copyright 2023 Google LLC.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * =============================================================================
+ */
+
+// TODO(mattSoulanille): Replace this with automatic polyfilling using core-js.
+export function *matchAll(str: string, regexp: RegExp): IterableIterator<RegExpMatchArray> {
+  // Remove the global flag since str.match does not work with it.
+  const flags = new Set(regexp.flags.split(''));
+  flags.delete('g');
+  regexp = new RegExp(regexp, [...flags].join(''));
+
+  let match = str.match(regexp);
+  let offset = 0;
+  let restOfStr = str;
+  while (match != null) {
+    if (match.index == null) {
+      console.error(match);
+      throw new Error(`Matched string '${match[0]}' has no index`);
+    }
+
+    // Remove up to and including the first match from the input string
+    // so the next loop can find the next match.
+    const matchEnd = match.index + match[0].length;
+    restOfStr = restOfStr.slice(matchEnd);
+
+    // Adjust the match to look like a result from matchAll.
+    match.index += offset;
+    match.input = str;
+
+    offset += matchEnd;
+    yield match;
+    match = restOfStr.match(regexp);
+  }
+}

tfjs-layers/src/layers/nlp/match_all_polyfill_test.ts

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+/**
+ * @license
+ * Copyright 2023 Google LLC.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * =============================================================================
+ */
+
+import {matchAll} from './match_all_polyfill';
+
+function format({match, index, input}: {match: string, index: number,
+                                        input: string}) {
+  const res: RegExpMatchArray = [match];
+  res.index = index;
+  res.input = input;
+  return jasmine.objectContaining(res);
+}
+
+describe('matchAll', () => {
+  it('finds all matches of a regexp on a string', () => {
+    const input = 'asdfasdfasdfasdf';
+    expect([...matchAll(input , /asd/g)]).toEqual([
+      {match: 'asd', index: 0, input},
+      {match: 'asd', index: 4, input},
+      {match: 'asd', index: 8, input},
+      {match: 'asd', index: 12, input},
+    ].map(format));
+  });
+
+  it('supports regexp flags', () => {
+    const input = 'asdfASDFasdfASDF';
+    // Case sensitive
+    expect([...matchAll(input, /asd/g)]).toEqual([
+      {match: 'asd', index: 0, input},
+      {match: 'asd', index: 8, input},
+    ].map(format));
+
+    // case insensitive
+    expect([...matchAll('asdfASDFasdfASDF', /asd/gi)]).toEqual([
+      {match: 'asd', index: 0, input},
+      {match: 'ASD', index: 4, input},
+      {match: 'asd', index: 8, input},
+      {match: 'ASD', index: 12, input},
+    ].map(format));
+  });
+});