wip test ordering of popular

lib/model/emoji.dart

@@ -283,7 +283,7 @@ class EmojiStoreImpl with EmojiStore {
   List<EmojiCandidate> _generateAllCandidates() {
     final results = <EmojiCandidate>[];
 
-    // Include the "popular" emoji in their canonical order
+    // Include the "popular" emoji, in their canonical order
     // relative to each other.
     results.addAll(zulipPopularEmojis);
 

test/model/emoji_test.dart

@@ -126,6 +126,40 @@ void main() {
       return store;
     }
 
+    test('popular emoji appear even when no server emoji data', () {
+      final store = prepare(unicodeEmoji: null);
+      check(store.allEmojiCandidates()).deepEquals([
+        ...arePopularCandidates,
+        isZulipCandidate(),
+      ]);
+    });
+
+    test('popular emoji appear in their canonical order', () {
+      // In the server's emoji data, have the popular emoji in a permuted order,
+      // and interspersed with other emoji.
+      final store = prepare(unicodeEmoji: {
+        '1f603': ['smiley'],
+        for (final candidate in zulipPopularEmojis.skip(3))
+          candidate.emojiCode: [candidate.emojiName, ...candidate.aliases],
+        '1f34a': ['orange', 'tangerine', 'mandarin'],
+        for (final candidate in zulipPopularEmojis.take(3))
+          candidate.emojiCode: [candidate.emojiName, ...candidate.aliases],
+        '1f516': ['bookmark'],
+      });
+      // In the allEmojiCandidates result, the popular emoji come first
+      // and are in their canonical order, even though the other Unicode emoji
+      // are in the same order they were given in.
+      check(store.allEmojiCandidates()).deepEquals([
+        for (final candidate in zulipPopularEmojis)
+          isUnicodeCandidate(candidate.emojiCode,
+            [candidate.emojiName, ...candidate.aliases]),
+        isUnicodeCandidate('1f603', ['smiley']),
+        isUnicodeCandidate('1f34a', ['orange', 'tangerine', 'mandarin']),
+        isUnicodeCandidate('1f516', ['bookmark']),
+        isZulipCandidate(),
+      ]);
+    });
+
     test('realm emoji overrides Unicode emoji', () {
       final store = prepare(realmEmoji: {
         '1': eg.realmEmojiItem(emojiCode: '1', emojiName: 'smiley'),
@@ -301,6 +335,45 @@ void main() {
       return view.results;
     }
 
+    test('results preserve order of popular emoji within each rank', () async {
+      // In other words, the sorting by rank is a stable sort.
+
+      // Full results list matches allEmojiCandidates.
+      check(prepare().allEmojiCandidates())
+        .deepEquals([...arePopularCandidates, isZulipCandidate()]);
+      check(await resultsOf(''))
+        .deepEquals([...arePopularResults, isZulipResult()]);
+
+      // Same list written out explicitly, for comparison with the cases below.
+      check(await resultsOf('')).deepEquals([
+        isUnicodeResult(names: ['+1', 'thumbs_up', 'like']),
+        isUnicodeResult(names: ['tada']),
+        isUnicodeResult(names: ['smile']),
+        isUnicodeResult(names: ['heart', 'love', 'love_you']),
+        isUnicodeResult(names: ['working_on_it', 'hammer_and_wrench', 'tools']),
+        isUnicodeResult(names: ['octopus']),
+        isZulipResult(),
+      ]);
+
+      check(await resultsOf('t')).deepEquals([
+        // prefix
+        isUnicodeResult(names: ['+1', 'thumbs_up', 'like']),
+        isUnicodeResult(names: ['tada']),
+        isUnicodeResult(names: ['working_on_it', 'hammer_and_wrench', 'tools']),
+        // other
+        isUnicodeResult(names: ['heart', 'love', 'love_you']),
+        isUnicodeResult(names: ['octopus']),
+      ]);
+
+      check(await resultsOf('h')).deepEquals([
+        // prefix
+        isUnicodeResult(names: ['heart', 'love', 'love_you']),
+        isUnicodeResult(names: ['working_on_it', 'hammer_and_wrench', 'tools']),
+        // other
+        isUnicodeResult(names: ['+1', 'thumbs_up', 'like']),
+      ]);
+    });
+
     test('results end-to-end', () async {
       // (See more detailed rank tests below, on EmojiAutocompleteQuery.)