Fix hover import prefix

Fixes #32735

Change-Id: I6830b61fe554065f9ec6e87f2ac24dfaffd67f35
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/390960
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>
Auto-Submit: Felipe Morschel <[email protected]>

Author: FMorschel

pkg/analysis_server/lib/src/computer/computer_hover.dart

@@ -57,7 +57,9 @@ class DartUnitHoverComputer {
         node is VariablePattern ||
         node is PatternFieldName ||
         node is DartPattern ||
-        (node is LibraryDirective && node.name2 == null)) {
+        (node is LibraryDirective && node.name2 == null) ||
+        (node is SimpleIdentifier && node.parent is ImportDirective) ||
+        node is ImportPrefixReference) {
       var range = _hoverRange(node, locationEntity);
       var hover = HoverInformation(range.offset, range.length);
       // element
@@ -198,6 +200,7 @@ class DartUnitHoverComputer {
       PatternFieldName() => node.name,
       WildcardPattern() => node.name,
       LibraryDirective() => node.libraryKeyword,
+      ImportPrefixReference() => node.name,
       _ => null,
     };
   }

pkg/analysis_server/lib/src/lsp/handlers/handler_hover.dart

@@ -59,12 +59,6 @@ class HoverHandler
       return null;
     }
 
-    // Import prefix tooltips are not useful currently.
-    // https://github.com/dart-lang/sdk/issues/32735
-    if (hover.elementKind == 'import prefix') {
-      return null;
-    }
-
     var content = StringBuffer();
     const divider = '---';
 

pkg/analysis_server/test/lsp/hover_test.dart

@@ -276,6 +276,99 @@ Type: `String`''';
     );
   }
 
+  Future<void> test_import_alias_dart() async {
+    var content = '''
+import 'dart:core' as [!l^ib!];
+''';
+    var expected = '''
+```dart
+'lib' is an import prefix for 'dart:core'
+```
+*package:test/main.dart*''';
+    await assertStringContents(content, equals(expected));
+  }
+
+  Future<void> test_import_alias_interpolation() async {
+    var content = '''
+// ignore: uri_with_interpolation
+import '\$bug.dart' as [!l^ib!];
+const bug = 'bug';
+''';
+    var expected = '''
+```dart
+'lib' is an import prefix for '<no-relative-uri>'
+```
+*package:test/main.dart*''';
+    await assertStringContents(content, equals(expected));
+  }
+
+  Future<void> test_import_alias_multiple_equal() async {
+    newFile('/home/my_project/lib/lib.dart', '''
+/// This is a string.
+library my.lib;
+''');
+    var content = '''
+import 'dart:math' as lib;
+import 'lib.dart' as [!l^ib!];
+''';
+    var expected = '''
+```dart
+'lib' is an import prefix for:
+- 'dart:math'
+- 'lib.dart'
+```
+*package:test/main.dart*''';
+    await assertStringContents(content, equals(expected));
+  }
+
+  Future<void> test_import_alias_package() async {
+    newFile('/home/my_project/lib/lib.dart', '''
+/// This is a string.
+library my.lib;
+''');
+    var content = '''
+import 'package:test/lib.dart' as [!l^ib!];
+''';
+    var expected = '''
+```dart
+'lib' is an import prefix for 'package:test/lib.dart'
+```
+*package:test/main.dart*''';
+    await assertStringContents(content, equals(expected));
+  }
+
+  Future<void> test_import_alias_project() async {
+    newFile('/home/my_project/lib/lib.dart', '''
+''');
+    var content = '''
+import 'lib.dart' as [!l^ib!];
+''';
+    var expected = '''
+```dart
+'lib' is an import prefix for 'lib.dart'
+```
+*package:test/main.dart*''';
+    await assertStringContents(content, equals(expected));
+  }
+
+  Future<void> test_import_prefix() async {
+    newFile('/home/my_project/lib/lib.dart', '''
+/// This is a string.
+library my.lib;
+class C {}
+''');
+    var content = '''
+import 'lib.dart' as lib;
+[!li^b!].C? c;
+''';
+    var expected = '''
+```dart
+'lib' is an import prefix for 'lib.dart'
+```
+*package:test/main.dart*''';
+    await assertStringContents(content, equals(expected));
+  }
+
   Future<void> test_localVariable_wildcard() async {
     var content = '''
 f() {

pkg/analyzer/lib/src/dart/element/display_string_builder.dart

@@ -252,13 +252,41 @@ class ElementDisplayStringBuilder {
   }
 
   void writePrefixElement(PrefixElementImpl element) {
-    _write('as ');
-    _write(element.displayName);
+    var libraryImports = element.imports;
+    if (libraryImports.isEmpty) {
+      _write('as ');
+      _write(element.displayName);
+      return;
+    }
+    _write("'${element.displayName}'");
+    _write(' is an import prefix for');
+    if (libraryImports case List(length: 1, :var first)) {
+      _write(" '${first.libraryName}'");
+      return;
+    }
+    _write(':');
+    for (var libraryImport in libraryImports) {
+      _write("\n- '${libraryImport.libraryName}'");
+    }
   }
 
   void writePrefixElement2(PrefixElementImpl2 element) {
-    _write('as ');
-    _write(element.displayName);
+    var libraryImports = element.imports;
+    if (element.imports.isEmpty) {
+      _write('as ');
+      _write(element.displayName);
+      return;
+    }
+    _write("'${element.displayName}'");
+    _write(' is an import prefix for');
+    if (libraryImports case List(length: 1, :var first)) {
+      _write(" '${first.libraryName}'");
+      return;
+    }
+    _write(':');
+    for (var libraryImport in libraryImports) {
+      _write("\n- '${libraryImport.libraryName}'");
+    }
   }
 
   void writeRecordType(RecordType type) {
@@ -609,3 +637,12 @@ class ElementDisplayStringBuilder {
 }
 
 enum _WriteFormalParameterKind { requiredPositional, optionalPositional, named }
+
+extension on LibraryImportElement {
+  String get libraryName {
+    if (uri case DirectiveUriWithRelativeUriString uri) {
+      return uri.relativeUriString;
+    }
+    return '<no-relative-uri>';
+  }
+}