fix(@angular-devkit/build-angular): fix countOccurences

And add testing for it.

packages/angular_devkit/build_angular/plugins/webpack/analytics.ts

@@ -42,14 +42,23 @@ export function countOccurrences(source: string, match: string, wordBreak = fals
   // We condition here so branch prediction happens out of the loop, not in it.
   if (wordBreak) {
     const re = /\w/;
-    for (let pos = source.lastIndexOf(match); pos >= 0; pos = source.lastIndexOf(match, pos - 1)) {
-      if (!(re.test(source[pos - 1]) || re.test(source[pos + match.length]))) {
+    for (let pos = source.lastIndexOf(match); pos >= 0; pos = source.lastIndexOf(match, pos)) {
+      if (!(re.test(source[pos - 1] || '') || re.test(source[pos + match.length] || ''))) {
         count++;  // 1 match, AH! AH! AH! 2 matches, AH! AH! AH!
       }
+
+      pos -= match.length;
+      if (pos < 0) {
+        break;
+      }
     }
   } else {
-    for (let pos = source.lastIndexOf(match); pos >= 0; pos = source.lastIndexOf(match, pos - 1)) {
+    for (let pos = source.lastIndexOf(match); pos >= 0; pos = source.lastIndexOf(match, pos)) {
       count++;  // 1 match, AH! AH! AH! 2 matches, AH! AH! AH!
+      pos -= match.length;
+      if (pos < 0) {
+        break;
+      }
     }
   }
 

packages/angular_devkit/build_angular/plugins/webpack/analytics_spec.ts

@@ -0,0 +1,95 @@
+/**
+ * @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 { countOccurrences } from './analytics';
+
+
+function _randomString(len: number) {
+  const charSpace = `0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ`;
+
+  let s = '';
+  for (let i = 0; i < len; i++) {
+    s += charSpace[Math.floor(Math.random() * charSpace.length)];
+  }
+
+  return s;
+}
+
+describe('countOccurrences', () => {
+  // Every use cases is a text, search, word break or not, and expected result.
+  const useCases: [string, string, boolean, number][] = [
+    ['abc1def1ghi1jkl1mno1pqrs1tuvw1xyz', '1', false, 7],  // 0
+    ['abc1def12ghi1jkl1mno12pqrs12tuvw1xyz12', '12', false, 4],  // 1
+    ['abc', 'abc', false, 1],  // 2
+    ['abc', 'abc', true, 1],  // 3
+    ['aaaaa', 'aaa', false, 1],  // 4
+    ['aa aaa', 'aaa', true, 1],  // 5
+    ['aaaaaa', 'aaa', false, 2],  // 6
+    ['aaa aaa', 'aaa', true, 2],  // 7
+    ['a', 'a', false, 1],  // 8
+    ['a', 'a', true, 1],  // 9
+  ];
+
+  useCases.forEach(([text, search, wordBreak, expected], i) => {
+    it(`works (${i})`, () => {
+      expect(countOccurrences(text, search, wordBreak)).toBe(expected);
+    });
+  });
+
+  // Random testing.
+  it('can count (random, wordBreak=false)', () => {
+    // Generate a random string with injected search strings in it.
+    let text = _randomString(10000);
+    const search = _randomString(100).toLowerCase();
+    const nb = Math.floor(Math.random() * 200 + 100);
+
+    // Insert nb search string in.
+    new Array(nb).fill(0)
+      // Map it with a random position.
+      .map(() => Math.floor(Math.random() * text.length))
+      // Sort from highest to lowest.
+      .sort((a, b) => b - a)
+      // Insert the search string for each position created this way.
+      .forEach(pos => {
+        text = text.slice(0, pos) + search + text.slice(pos);
+      });
+
+    expect(countOccurrences(text, search, false)).toBe(nb);
+    expect(countOccurrences(text, search, true)).toBe(0);
+  });
+
+  it('can count (random, wordBreak=true)', () => {
+    // Generate a random string with injected search strings in it.
+    let text = _randomString(10000);
+    const search = _randomString(100).toLowerCase();
+    let nb = Math.floor(Math.random() * 200 + 100);
+
+    // Insert nb search string in.
+    new Array(nb).fill(0)
+    // Map it with a random position.
+      .map(() => Math.floor(Math.random() * text.length))
+      // Sort from highest to lowest.
+      .sort((a, b) => b - a)
+      // Insert the search string for each position created this way.
+      .forEach(pos => {
+        switch (Math.floor(Math.random() * 5)) {
+          case 0:
+            // Do not insert a wordbreak.
+            text = text.slice(0, pos) + search + text.slice(pos);
+            nb--;
+            break;
+
+          case 1: text = text.slice(0, pos) + ' ' + search + ' ' + text.slice(pos); break;
+          case 2: text = text.slice(0, pos) + '(' + search + '$' + text.slice(pos); break;
+          case 3: text = text.slice(0, pos) + '|' + search + ')' + text.slice(pos); break;
+          case 4: text = text.slice(0, pos) + '-' + search + '.' + text.slice(pos); break;
+        }
+      });
+
+    expect(countOccurrences(text, search, true)).toBe(nb);
+  });
+});