autocomplete [nfc]: Separate ComposeAutocompleteQuery/Result from Mention-etc.

The two concepts have meant the same set of possible values so far,
because @-mentions are the only type of autocomplete we've had so far
in the compose box's content input.  As a result we've taken some
shortcuts by conflating them.

But as we introduce other types of autocomplete in the content input,
like for emoji and #-mentions, we have some places that will need to
refer to the more general concept while others refer to the more
specific one.  So separate them out.

Author: gnprice

lib/model/autocomplete.dart

@@ -9,7 +9,7 @@ import 'narrow.dart';
 import 'store.dart';
 
 extension ComposeContentAutocomplete on ComposeContentController {
-  AutocompleteIntent<MentionAutocompleteQuery>? autocompleteIntent() {
+  AutocompleteIntent<ComposeAutocompleteQuery>? autocompleteIntent() {
     if (!selection.isValid || !selection.isNormalized) {
       // We don't require [isCollapsed] to be true because we've seen that
       // autocorrect and even backspace involve programmatically expanding the
@@ -208,6 +208,10 @@ abstract class AutocompleteView<QueryT extends AutocompleteQuery, ResultT extend
 
   final PerAccountStore store;
 
+  /// True just if this [AutocompleteView] is of the appropriate type
+  /// to handle the given query.
+  bool acceptsQuery(AutocompleteQuery query) => query is QueryT;
+
   /// The last query this [AutocompleteView] was asked to perform for the user.
   ///
   /// If this view-model is currently performing a search,
@@ -311,7 +315,12 @@ abstract class AutocompleteView<QueryT extends AutocompleteQuery, ResultT extend
   }
 }
 
-/// An [AutocompleteView] for an @-mention autocomplete interaction.
+/// An [AutocompleteView] for an autocomplete interaction
+/// in the compose box's content input.
+typedef ComposeAutocompleteView = AutocompleteView<ComposeAutocompleteQuery, ComposeAutocompleteResult>;
+
+/// An [AutocompleteView] for an @-mention autocomplete interaction,
+/// an example of a [ComposeAutocompleteView].
 class MentionAutocompleteView extends AutocompleteView<MentionAutocompleteQuery, MentionAutocompleteResult> {
   MentionAutocompleteView._({
     required super.store,
@@ -572,13 +581,27 @@ abstract class AutocompleteQuery {
   }
 }
 
+/// Any autocomplete query in the compose box's content input.
+abstract class ComposeAutocompleteQuery extends AutocompleteQuery {
+  ComposeAutocompleteQuery(super.raw);
+
+  /// Construct an [AutocompleteView] initialized with this query
+  /// and ready to handle queries of the same type.
+  ComposeAutocompleteView initViewModel(PerAccountStore store, Narrow narrow);
+}
+
 /// A @-mention autocomplete query, used by [MentionAutocompleteView].
-class MentionAutocompleteQuery extends AutocompleteQuery {
+class MentionAutocompleteQuery extends ComposeAutocompleteQuery {
   MentionAutocompleteQuery(super.raw, {this.silent = false});
 
   /// Whether the user wants a silent mention (@_query, vs. @query).
   final bool silent;
 
+  @override
+  MentionAutocompleteView initViewModel(PerAccountStore store, Narrow narrow) {
+    return MentionAutocompleteView.init(store: store, narrow: narrow, query: this);
+  }
+
   bool testUser(User user, AutocompleteDataCache cache) {
     // TODO(#236) test email too, not just name
 
@@ -636,13 +659,18 @@ class AutocompleteDataCache {
 /// have corresponding subclasses of [AutocompleteResult] they might produce.
 class AutocompleteResult {}
 
+/// A result from some autocomplete interaction in
+/// the compose box's content input, initiated by a [ComposeAutocompleteQuery]
+/// and managed by some [ComposeAutocompleteView].
+sealed class ComposeAutocompleteResult extends AutocompleteResult {}
+
 /// A result from an @-mention autocomplete interaction,
 /// managed by a [MentionAutocompleteView].
 ///
 /// This is abstract because there are several kinds of result
 /// that can all be offered in the same @-mention autocomplete interaction:
 /// a user, a wildcard, or a user group.
-sealed class MentionAutocompleteResult extends AutocompleteResult {}
+sealed class MentionAutocompleteResult extends ComposeAutocompleteResult {}
 
 /// An autocomplete result for an @-mention of an individual user.
 class UserMentionAutocompleteResult extends MentionAutocompleteResult {

lib/widgets/autocomplete.dart

@@ -39,16 +39,23 @@ class _AutocompleteFieldState<QueryT extends AutocompleteQuery, ResultT extends
 
   void _handleControllerChange() {
     final newQuery = widget.autocompleteIntent()?.query;
+    // First, tear down the old view-model if necessary.
+    if (_viewModel != null
+        && (newQuery == null
+            || !_viewModel!.acceptsQuery(newQuery))) {
+      // The autocomplete interaction has ended, or has switched to a
+      // different kind of autocomplete (e.g. @-mention vs. emoji).
+      _viewModel!.dispose(); // removes our listener
+      _viewModel = null;
+      _resultsToDisplay = [];
+    }
+    // Then, update the view-model or build a new one.
     if (newQuery != null) {
       if (_viewModel == null) {
         _initViewModel(newQuery);
-      }
-      _viewModel!.query = newQuery;
-    } else {
-      if (_viewModel != null) {
-        _viewModel!.dispose(); // removes our listener
-        _viewModel = null;
-        _resultsToDisplay = [];
+      } else {
+        assert(_viewModel!.acceptsQuery(newQuery));
+        _viewModel!.query = newQuery;
       }
     }
   }
@@ -144,7 +151,7 @@ class _AutocompleteFieldState<QueryT extends AutocompleteQuery, ResultT extends
   }
 }
 
-class ComposeAutocomplete extends AutocompleteField<MentionAutocompleteQuery, MentionAutocompleteResult> {
+class ComposeAutocomplete extends AutocompleteField<ComposeAutocompleteQuery, ComposeAutocompleteResult> {
   const ComposeAutocomplete({
     super.key,
     required this.narrow,
@@ -159,30 +166,34 @@ class ComposeAutocomplete extends AutocompleteField<MentionAutocompleteQuery, Me
   ComposeContentController get controller => super.controller as ComposeContentController;
 
   @override
-  AutocompleteIntent<MentionAutocompleteQuery>? autocompleteIntent() => controller.autocompleteIntent();
+  AutocompleteIntent<ComposeAutocompleteQuery>? autocompleteIntent() => controller.autocompleteIntent();
 
   @override
-  MentionAutocompleteView initViewModel(BuildContext context, MentionAutocompleteQuery query) {
+  ComposeAutocompleteView initViewModel(BuildContext context, ComposeAutocompleteQuery query) {
     final store = PerAccountStoreWidget.of(context);
-    return MentionAutocompleteView.init(store: store, narrow: narrow, query: query);
+    return query.initViewModel(store, narrow);
   }
 
-  void _onTapOption(BuildContext context, MentionAutocompleteResult option) {
+  void _onTapOption(BuildContext context, ComposeAutocompleteResult option) {
     // Probably the same intent that brought up the option that was tapped.
     // If not, it still shouldn't be off by more than the time it takes
     // to compute the autocomplete results, which we do asynchronously.
     final intent = autocompleteIntent();
     if (intent == null) {
       return; // Shrug.
     }
+    final query = intent.query;
 
     final store = PerAccountStoreWidget.of(context);
     final String replacementString;
     switch (option) {
       case UserMentionAutocompleteResult(:var userId):
+        if (query is! MentionAutocompleteQuery) {
+          return; // Shrug; similar to `intent == null` case above.
+        }
         // TODO(i18n) language-appropriate space character; check active keyboard?
         //   (maybe handle centrally in `controller`)
-        replacementString = '${mention(store.users[userId]!, silent: intent.query.silent, users: store.users)} ';
+        replacementString = '${mention(store.users[userId]!, silent: query.silent, users: store.users)} ';
     }
 
     controller.value = intent.textEditingValue.replaced(
@@ -194,26 +205,40 @@ class ComposeAutocomplete extends AutocompleteField<MentionAutocompleteQuery, Me
   }
 
   @override
-  Widget buildItem(BuildContext context, int index, MentionAutocompleteResult option) {
+  Widget buildItem(BuildContext context, int index, ComposeAutocompleteResult option) {
+    final child = switch (option) {
+      MentionAutocompleteResult() => _MentionAutocompleteItem(option: option),
+    };
+    return InkWell(
+      onTap: () {
+        _onTapOption(context, option);
+      },
+      child: child);
+  }
+}
+
+class _MentionAutocompleteItem extends StatelessWidget {
+  const _MentionAutocompleteItem({required this.option});
+
+  final MentionAutocompleteResult option;
+
+  @override
+  Widget build(BuildContext context) {
     Widget avatar;
     String label;
     switch (option) {
       case UserMentionAutocompleteResult(:var userId):
         avatar = Avatar(userId: userId, size: 32, borderRadius: 3);
         label = PerAccountStoreWidget.of(context).users[userId]!.fullName;
     }
-    return InkWell(
-      onTap: () {
-        _onTapOption(context, option);
-      },
-      child: Padding(
-        padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
-        child: Row(
-          children: [
-            avatar,
-            const SizedBox(width: 8),
-            Text(label),
-          ])));
+
+    return Padding(
+      padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
+      child: Row(children: [
+        avatar,
+        const SizedBox(width: 8),
+        Text(label),
+      ]));
   }
 }
 

test/model/autocomplete_checks.dart

@@ -3,7 +3,7 @@ import 'package:zulip/model/autocomplete.dart';
 import 'package:zulip/widgets/compose_box.dart';
 
 extension ComposeContentControllerChecks on Subject<ComposeContentController> {
-  Subject<AutocompleteIntent<MentionAutocompleteQuery>?> get autocompleteIntent => has((c) => c.autocompleteIntent(), 'autocompleteIntent');
+  Subject<AutocompleteIntent<ComposeAutocompleteQuery>?> get autocompleteIntent => has((c) => c.autocompleteIntent(), 'autocompleteIntent');
 }
 
 extension ComposeTopicControllerChecks on Subject<ComposeTopicController> {