emoji: Recognize word-aligned matches in ranking

Fixes #1068.

Author: gnprice

lib/model/emoji.dart

@@ -337,7 +337,15 @@ enum EmojiMatchQuality {
   /// The query matches a prefix of the emoji name, but not the whole name.
   prefix,
 
-  /// The query matches somewhere in the emoji name, but not at the start.
+  /// The query matches starting at the start of a word in the emoji name,
+  /// but not the start of the whole name.
+  ///
+  /// For example a name "ab_cd_ef" would match queries "c" or "cd_e"
+  /// at this level, but not a query "b_cd_ef".
+  wordAligned,
+
+  /// The query matches somewhere in the emoji name,
+  /// but not at the start of any word.
   other;
 
   /// The best possible quality of match.
@@ -448,25 +456,17 @@ class EmojiAutocompleteQuery extends ComposeAutocompleteQuery {
     // See also commentary in [_rankResult].
 
     // TODO(#1067) this assumes emojiName is already lower-case (and no diacritics)
-    if (emojiName == _adjusted)          return EmojiMatchQuality.exact;
-    if (emojiName.startsWith(_adjusted)) return EmojiMatchQuality.prefix;
-    if (_nameMatches(emojiName))         return EmojiMatchQuality.other;
-    return null;
-  }
-
-  bool _nameMatches(String emojiName) {
+    if (emojiName == _adjusted)           return EmojiMatchQuality.exact;
+    if (emojiName.startsWith(_adjusted))  return EmojiMatchQuality.prefix;
+    if (emojiName.contains(_sepAdjusted)) return EmojiMatchQuality.wordAligned;
     if (!_adjusted.contains(_separator)) {
       // If the query is a single token (doesn't contain a separator),
-      // the match can be anywhere in the string.
-      return emojiName.contains(_adjusted);
+      // allow a match anywhere in the string, too.
+      if (emojiName.contains(_adjusted))  return EmojiMatchQuality.other;
+    } else {
+      // Otherwise, require at least a word-aligned match.
     }
-
-    // If there is a separator in the query, then we
-    // require the match to start at the start of a token.
-    // (E.g. for 'ab_cd_ef', query could be 'ab_c' or 'cd_ef',
-    // but not 'b_cd_ef'.)
-    assert(!emojiName.startsWith(_adjusted)); // checked before calling this method
-    return emojiName.contains(_sepAdjusted);
+    return null;
   }
 
   /// A measure of the result's quality in the context of the query,
@@ -475,11 +475,9 @@ class EmojiAutocompleteQuery extends ComposeAutocompleteQuery {
     // Compare sort_emojis in Zulip web:
     //   https://github.com/zulip/zulip/blob/83a121c7e/web/shared/src/typeahead.ts#L322-L382
     //
-    // Behavior differences we should or might copy, TODO(#1068):
-    //  * Web ranks matches starting at a word boundary ahead of
-    //    other non-prefix matches; we don't yet.
-    //  * Relatedly, web favors popular emoji only upon a word-aligned match.
+    // Behavior differences we might copy, TODO:
     //  * Web ranks each name of a Unicode emoji separately.
+    //  * Web recognizes a word-aligned match starting after [ /-] as well as [_].
     //
     // Behavior differences that web should probably fix, TODO(web):
     //  * Among popular emoji with non-exact matches,
@@ -508,15 +506,15 @@ class EmojiAutocompleteQuery extends ComposeAutocompleteQuery {
       ReactionType.unicodeEmoji => false,
     };
     return switch (matchQuality) {
-      EmojiMatchQuality.exact  => 0,
-      EmojiMatchQuality.prefix => isPopular ? 1 : isCustomEmoji ? 3 : 4,
-      // TODO word-boundary vs. not
-      EmojiMatchQuality.other  => isPopular ? 2 : isCustomEmoji ? 5 : 6,
+      EmojiMatchQuality.exact       => 0,
+      EmojiMatchQuality.prefix      => isPopular ? 1 : isCustomEmoji ? 3 : 5,
+      EmojiMatchQuality.wordAligned => isPopular ? 2 : isCustomEmoji ? 4 : 6,
+      EmojiMatchQuality.other       =>                 isCustomEmoji ? 7 : 8,
     };
   }
 
   /// The number of possible values returned by [_rankResult].
-  static const _numResultRanks = 7;
+  static const _numResultRanks = 9;
 
   @override
   String toString() {

test/model/emoji_test.dart

@@ -347,7 +347,7 @@ void main() {
       check(matchOfName('o', 'open_book')).prefix;
       check(matchOfName('open', 'open_book')).prefix;
       check(matchOfName('pe', 'open_book')).other;
-      check(matchOfName('boo', 'open_book')).other;
+      check(matchOfName('boo', 'open_book')).wordAligned;
       check(matchOfName('ok', 'open_book')).other;
     });
 
@@ -359,7 +359,7 @@ void main() {
       check(matchOfName('pen_', 'open_book')).none;
       check(matchOfName('n_b', 'open_book')).none;
 
-      check(matchOfName('blue_dia', 'large_blue_diamond')).other;
+      check(matchOfName('blue_dia', 'large_blue_diamond')).wordAligned;
     });
 
     test('spaces in query behave as underscores', () {
@@ -370,7 +370,7 @@ void main() {
       check(matchOfName('pen ', 'open_book')).none;
       check(matchOfName('n b', 'open_book')).none;
 
-      check(matchOfName('blue dia', 'large_blue_diamond')).other;
+      check(matchOfName('blue dia', 'large_blue_diamond')).wordAligned;
     });
 
     test('query is lower-cased', () {
@@ -389,13 +389,17 @@ void main() {
       check(matchOfNames('open b', ['x', 'open_book'])).prefix;
       check(matchOfNames('pen_', ['x', 'open_book'])).none;
 
+      check(matchOfNames('blue_dia', ['x', 'large_blue_diamond'])).wordAligned;
+
       check(matchOfNames('Smi', ['x', 'smile'])).prefix;
     });
 
     test('best match among name and aliases prevails', () {
-      check(matchOfNames('a', ['ab', 'a', 'ba', 'x'])).exact;
-      check(matchOfNames('a', ['ba', 'ab', 'x'])).prefix;
-      check(matchOfNames('a', ['ba', 'ab'])).prefix;
+      check(matchOfNames('a', ['ab', 'a', 'b_a', 'ba', 'x'])).exact;
+      check(matchOfNames('a', ['ba', 'ab', 'b_a', 'x'])).prefix;
+      check(matchOfNames('a', ['ba', 'ab', 'b_a'])).prefix;
+      check(matchOfNames('a', ['ba', 'b_a', 'x'])).wordAligned;
+      check(matchOfNames('a', ['b_a', 'ba'])).wordAligned;
       check(matchOfNames('a', ['ba', 'x'])).other;
       check(matchOfNames('a', ['x', 'y', 'z'])).none;
     });
@@ -441,7 +445,7 @@ void main() {
       check(matchOf('eqeq', realmCandidate('eqeq'))).exact;
       check(matchOf('open_', realmCandidate('open_book'))).prefix;
       check(matchOf('n_b', realmCandidate('open_book'))).none;
-      check(matchOf('blue dia', realmCandidate('large_blue_diamond'))).other;
+      check(matchOf('blue dia', realmCandidate('large_blue_diamond'))).wordAligned;
       check(matchOf('Smi', realmCandidate('smile'))).prefix;
     });
 
@@ -476,10 +480,12 @@ void main() {
 
     final octopus = unicode(['octopus'], emojiCode: '1f419');
     final workingOnIt = unicode(['working_on_it'], emojiCode: '1f6e0');
+    final love = unicode(['love'], emojiCode: '2764'); // aka :heart:
 
-    test('ranks exact before prefix before other match', () {
+    test('ranks match quality exact/prefix/word-aligned/other', () {
       checkPrecedes('o', unicode(['o']), unicode(['onion']));
-      checkPrecedes('o', unicode(['onion']), unicode(['book']));
+      checkPrecedes('o', unicode(['onion']), unicode(['squared_ok']));
+      checkPrecedes('o', unicode(['squared_ok']), unicode(['book']));
     });
 
     test('ranks popular before realm before other Unicode', () {
@@ -498,28 +504,51 @@ void main() {
       checkPrecedes('o', octopus, realmCandidate('open_book'));
     });
 
-    test('ranks popular-vs-not more significant than prefix/other', () {
-      // Popular other beats realm prefix.
+    test('ranks popular-vs-not more significant than prefix/word-aligned', () {
+      // Popular word-aligned beats realm prefix.
       checkPrecedes('o', workingOnIt, realmCandidate('open_book'));
     });
 
-    test('ranks prefix/other more significant than custom/other', () {
-      // Generic Unicode prefix beats realm other.
-      checkPrecedes('o', unicode(['ok']), realmCandidate('yo'));
+    test('ranks popular as if generic when non-word-aligned', () {
+      // Generic word-aligned beats popular other.
+      checkPrecedes('o', unicode(['squared_ok']), love);
+      // Popular other ranks below even custom other…
+      checkPrecedes('o', realmCandidate('yo'), love);
+      // … and same as generic Unicode other.
+      checkSameRank('o', love, unicode(['book']));
+
+      // And that emoji really does count as popular,
+      // beating custom emoji when both have a prefix match.
+      checkPrecedes('l', love, realmCandidate('logs'));
+    });
+
+    test('ranks custom/other more significant than prefix/word-aligned', () {
+      // Custom word-aligned beats generic prefix.
+      checkPrecedes('o', realmCandidate('laughing_blue_octopus'),
+                         unicode(['ok']));
+    });
+
+    test('ranks word-aligned/other more significant than custom/other', () {
+      // Generic Unicode word-aligned beats realm other.
+      checkPrecedes('o', unicode(['squared_ok']), realmCandidate('yo'));
     });
 
     test('full list of ranks', () {
       check([
         rankOf('o', unicode(['o'])),              // exact (generic)
         rankOf('o', octopus),                     // prefix popular
-        rankOf('o', workingOnIt),                 // other popular
+        rankOf('o', workingOnIt),                 // word-aligned popular
         rankOf('o', realmCandidate('open_book')), // prefix realm
         rankOf('z', zulipCandidate()),            //  == prefix :zulip:
+        rankOf('y', realmCandidate('thank_you')), // word-aligned realm
+            // (word-aligned :zulip: is impossible because the name is one word)
         rankOf('o', unicode(['ok'])),             // prefix generic
+        rankOf('o', unicode(['squared_ok'])),     // word-aligned generic
         rankOf('o', realmCandidate('yo')),        // other realm
         rankOf('p', zulipCandidate()),            //  == other :zulip:
         rankOf('o', unicode(['book'])),           // other generic
-      ]).deepEquals([0, 1, 2, 3, 3, 4, 5, 5, 6]);
+        rankOf('o', love),                        //  == other popular
+      ]).deepEquals([0, 1, 2, 3, 3, 4, 5, 6, 7, 7, 8, 8]);
     });
   });
 }
@@ -548,6 +577,7 @@ extension EmojiCandidateChecks on Subject<EmojiCandidate> {
 extension EmojiMatchQualityChecks on Subject<EmojiMatchQuality?> {
   void get exact => equals(EmojiMatchQuality.exact);
   void get prefix => equals(EmojiMatchQuality.prefix);
+  void get wordAligned => equals(EmojiMatchQuality.wordAligned);
   void get other => equals(EmojiMatchQuality.other);
   void get none => isNull();
 }