Searches with regex control characters should not crash (#1579)

Fix #1578

frontend/lib/prepare-examples.js

@@ -1,3 +1,5 @@
+import escapeStringRegexp from 'escape-string-regexp';
+
 export function exampleMatchesRegex(example, regex) {
   const { title, keywords } = example;
   const haystack = [title].concat(keywords).join(' ');
@@ -6,7 +8,8 @@ export function exampleMatchesRegex(example, regex) {
 
 export function predicateFromQuery(query) {
   if (query) {
-    const regex = new RegExp(query, 'i'); // Case-insensitive.
+    const escaped = escapeStringRegexp(query);
+    const regex = new RegExp(escaped, 'i'); // Case-insensitive.
     return example => exampleMatchesRegex(example, regex);
   } else {
     return () => true;

frontend/lib/prepare-examples.spec.js

@@ -0,0 +1,20 @@
+import { test, given, forCases } from 'sazerac';
+import { predicateFromQuery } from './prepare-examples';
+
+describe('Badge example functions', function() {
+  const exampleMatchesQuery =
+    (example, query) => predicateFromQuery(query)(example);
+
+  test(exampleMatchesQuery, () => {
+    forCases([
+      given({ title: 'node version' }, 'npm'),
+    ]).expect(false);
+
+    forCases([
+      given({ title: 'node version', keywords: ['npm'] }, 'node'),
+      given({ title: 'node version', keywords: ['npm'] }, 'npm'),
+      // https://github.com/badges/shields/issues/1578
+      given({ title: 'c++ is the best language' }, 'c++'),
+    ]).expect(true);
+  });
+});

package.json

@@ -25,6 +25,7 @@
     "camp": "~17.2.1",
     "chrome-web-store-item-property": "~1.1.2",
     "dot": "~1.1.2",
+    "escape-string-regexp": "^1.0.5",
     "gm": "^1.23.0",
     "json-autosave": "~1.1.2",
     "jsonpath": "~1.0.0",