Cache element docs (and add to completions) (#23694).

pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library test.services.completion.contributor.dart.imported_ref;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart'
     hide Element, ElementKind;
 import 'package:analysis_server/src/protocol_server.dart';
 import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
@@ skipping 27 matching lines @@
     addSource('/libA.dart', 'library A; @deprecated enum E { one, two }');
     addTestSource('import "/libA.dart"; main() {^}');
     await computeSuggestions();
     // TODO(danrube) investigate why suggestion/element is not deprecated
     // when AST node has correct @deprecated annotation
     assertSuggestEnum('E', isDeprecated: true);
     assertNotSuggested('one');
     assertNotSuggested('two');
   }
 
+  test_doc_class() async {
+    addSource(
+        '/libA.dart',
+        r'''
+library A;
+/// My class.
+/// Short description.
+///
+/// Longer description.
+class A {}
+''');
+    addTestSource('import "/libA.dart"; main() {^}');
+
+    await computeSuggestions();
+
+    CompletionSuggestion suggestion = assertSuggestClass('A');
+    expect(suggestion.docSummary, 'My class.\nShort description.');
+    expect(suggestion.docComplete,
+        'My class.\nShort description.\n\nLonger description.');
+  }
+
+  test_doc_function() async {
+    resolveSource(
+        '/libA.dart',
+        r'''
+library A;
+/// My function.
+/// Short description.
+///
+/// Longer description.
+int myFunc() {}
+''');
+    addTestSource('import "/libA.dart"; main() {^}');
+
+    await computeSuggestions();
+
+    CompletionSuggestion suggestion = assertSuggestFunction('myFunc', 'int');
+    expect(suggestion.docSummary, 'My function.\nShort description.');
+    expect(suggestion.docComplete,
+        'My function.\nShort description.\n\nLonger description.');
+  }
+
+  test_doc_function_c_style() async {
+    resolveSource(
+        '/libA.dart',
+        r'''
+library A;
+/**
+ * My function.
+ * Short description.
+ *
+ * Longer description.
+ */
+int myFunc() {}
+''');
+    addTestSource('import "/libA.dart"; main() {^}');
+
+    await computeSuggestions();
+
+    CompletionSuggestion suggestion = assertSuggestFunction('myFunc', 'int');
+    expect(suggestion.docSummary, 'My function.\nShort description.');
+    expect(suggestion.docComplete,
+        'My function.\nShort description.\n\nLonger description.');
+  }
+  
   test_enum() async {
     addSource('/libA.dart', 'library A; enum E { one, two }');
     addTestSource('import "/libA.dart"; main() {^}');
     await computeSuggestions();
     assertSuggestEnum('E');
     assertNotSuggested('one');
     assertNotSuggested('two');
   }
 
   test_function_parameters_mixed_required_and_named() async {
@@ skipping 4243 matching lines @@
     assertNotSuggested('foo2');
     assertNotSuggested('bar2');
     assertNotSuggested('_B');
     assertNotSuggested('Y');
     assertNotSuggested('C');
     assertNotSuggested('f');
     assertNotSuggested('x');
     assertNotSuggested('e');
   }
 }