[analysis_server] Fix == overrides being truncated in LSP

The LSP completion mapping currently does some manipulation of values to fit better into the different fields LSP supports (to improve formatting and filtering). The code that splits the label on `=>` was also matching `==` in overrides but should not.

This is a simple fix to the regex to solve the issue, although longer-term (or at least if we see other issues as a result of this manipulation) this logic should be pushed up to the source so we have reliable fields and don't need to split things this way.

Fixes #56336

Change-Id: I056489df5aba417cab9162e027eb97579f71756b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/378200
Reviewed-by: Brian Wilkerson <[email protected]>
Reviewed-by: Phil Quitslund <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: DanTup

pkg/analysis_server/lib/src/lsp/mapping.dart

@@ -59,8 +59,8 @@ final sortTextMaxValue = int.parse('9' * maximumRelevance.toString().length);
 
 /// A regex used for splitting the display text in a completion so that
 /// filterText only includes the symbol name and not any additional text (such
-/// as parens, ` => `).
-final _completionFilterTextSplitPattern = RegExp(r'[=\(]');
+/// as parens, ` => `). Match `=>` but not `==` (which may appear in overrides).
+final _completionFilterTextSplitPattern = RegExp(r'=>|[\(]');
 
 /// A regex to extract the type name from the parameter string of a setter
 /// completion item.
@@ -1018,6 +1018,9 @@ lsp.CompletionItem toCompletionItem(
   // Only do this if label doesn't start with the pattern, because if it does
   // (for example for a closure `(a, b) {}`) we'll end up with an empty string
   // but we should instead use the whole label.
+
+  // TODO(dantup): Consider including more of these raw fields in the original
+  //  suggestion to avoid needing to manipulate them in this way here.
   var filterText = !label.startsWith(_completionFilterTextSplitPattern)
       ? label.split(_completionFilterTextSplitPattern).first.trim()
       : label;

pkg/analysis_server/test/lsp/completion_dart_test.dart

@@ -517,7 +517,24 @@ void f() {
         detail: 'String');
   }
 
-  Future<void> test_local_override_annotation() async {
+  Future<void> test_local_override_annotation_equals() async {
+    var content = '''
+class Base {
+}
+
+class Derived extends Base {
+  @over^
+}
+''';
+    await expectLabels(content,
+        label: 'override ==',
+        labelDetail: '(…) → bool',
+        labelDescription: null,
+        filterText: null,
+        detail: '(Object other) → bool');
+  }
+
+  Future<void> test_local_override_annotation_method() async {
     var content = '''
 class Base {
   String aa(String a) => '';
@@ -1901,7 +1918,7 @@ void f() {
   /// the correct narrowed type in the `detail` field.
   ///
   /// https://github.com/Dart-Code/Dart-Code/issues/4499
-  Future<void> test_getter_barrowedBySubclass() async {
+  Future<void> test_getter_narrowedBySubclass() async {
     var content = '''
 void f(MyItem item) {
   item.na^