Fix tag service to work with ASCII chars

The regex-ex was not capturing words at the start of a line which had ASCII characters.

This fix first splits the string based on words and searches for any match and then additionally checks the entire string against the query

src/sidebar/services/tags.js

@@ -41,12 +41,15 @@ export class TagsService {
     //   (e.g. tag "pink banana" matches query "ban"), OR
     // * tag has substring query occurring after a non-word character
     //   (e.g. tag "pink!banana" matches query "ban")
-    let regex = new RegExp('(\\W|\\b)' + query, 'i');
     return savedTags.filter(tag => {
-      if (tag.match(regex)) {
-        if (limit === null || resultCount < limit) {
+      const words = tag.split(/\W+/);
+      let regex = new RegExp(`^${query}`, 'i'); // Only match the start of the string
       // limit allows a subset of the results
       // See https://github.com/hypothesis/client/issues/1606
+      if (limit === null || resultCount < limit) {
+        const matches =
+          words.some(word => word.match(regex)) || tag.match(regex);
+        if (matches) {
           ++resultCount;
           return true;
         }

src/sidebar/services/test/tags-test.js

@@ -56,6 +56,12 @@ describe('TagsService', () => {
         count: 1,
         updated: stamp,
       },
+      'žŸ¡¢£¤¥¦§': {
+        // ASCII chars
+        text: 'žŸ¡¢£¤¥¦§',
+        count: 1,
+        updated: stamp,
+      },
     };
     const savedTagsList = Object.keys(savedTagsMap);
 
@@ -83,6 +89,10 @@ describe('TagsService', () => {
       assert.deepEqual(tags.filter('b', 2), ['bar', 'bar argon']);
       assert.deepEqual(tags.filter('b', 3), ['bar', 'bar argon', 'banana']);
     });
+
+    it('returns ASCII tags that start with the query string', () => {
+      assert.deepEqual(tags.filter('žŸ¡'), ['žŸ¡¢£¤¥¦§']);
+    });
   });
 
   describe('#store', () => {
@@ -122,6 +132,7 @@ describe('TagsService', () => {
         'bar argon',
         'future',
         'argon',
+        'žŸ¡¢£¤¥¦§',
       ]);
     });
   });