Remove adding prefixes for auto imports.

Adding import prefixes often has false positives.
At this point I think that this feature does more harm than benefit.

R=brianwilkerson@google.com

Bug: dart-lang/sdk#38326
Change-Id: I99e3400aebc062d9de3c298d7ed58520534d061c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/116746
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analysis_server/lib/src/domain_completion.dart

@@ -19,7 +19,6 @@ import 'package:analysis_server/src/services/completion/dart/completion_manager.
 import 'package:analysis_server/src/services/completion/token_details/token_detail_builder.dart';
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/dart/analysis/session.dart';
-import 'package:analyzer/dart/element/element.dart' as analyzer;
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer_plugin/protocol/protocol.dart' as plugin;
 import 'package:analyzer_plugin/protocol/protocol_common.dart';
@@ -199,46 +198,10 @@ class CompletionDomainHandler extends AbstractRequestHandler {
         var analysisDriver = server.getAnalysisDriver(file);
         var session = analysisDriver.currentSession;
 
-        var fileElement = await session.getUnitElement(file);
-        var libraryPath = fileElement.element.librarySource.fullName;
-
-        var resolvedLibrary = await session.getResolvedLibrary(libraryPath);
-
-        analyzer.LibraryElement requestedLibraryElement;
-        try {
-          requestedLibraryElement = await session.getLibraryByUri(
-            library.uriStr,
-          );
-        } on ArgumentError catch (e) {
-          server.sendResponse(Response.invalidParameter(
-            request,
-            'uri',
-            'Invalid URI: ${library.uriStr}\n$e',
-          ));
-          return;
-        }
-
-        var requestedElement =
-            requestedLibraryElement.exportNamespace.get(requestedName);
-        if (requestedElement == null) {
-          server.sendResponse(Response.invalidParameter(
-            request,
-            'label',
-            'No such element: $requestedName',
-          ));
-          return;
-        }
-
         var completion = params.label;
         var builder = DartChangeBuilder(session);
-        await builder.addFileEdit(libraryPath, (builder) {
-          var result = builder.importLibraryElement(
-            targetLibrary: resolvedLibrary,
-            targetPath: libraryPath,
-            targetOffset: params.offset,
-            requestedLibrary: requestedLibraryElement,
-            requestedElement: requestedElement,
-          );
+        await builder.addFileEdit(file, (builder) {
+          var result = builder.importLibraryElement(library.uri);
           if (result.prefix != null) {
             completion = '${result.prefix}.$completion';
           }

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

@@ -77,11 +77,6 @@ class CompletionResolveHandler
         var analysisDriver = server.getAnalysisDriver(data.file);
         var session = analysisDriver.currentSession;
 
-        var fileElement = await session.getUnitElement(data.file);
-        var libraryPath = fileElement.element.librarySource.fullName;
-
-        var resolvedLibrary = await session.getResolvedLibrary(libraryPath);
-
         if (token.isCancellationRequested) {
           return cancelled();
         }
@@ -115,14 +110,8 @@ class CompletionResolveHandler
 
         var newInsertText = item.insertText ?? item.label;
         final builder = DartChangeBuilder(session);
-        await builder.addFileEdit(libraryPath, (builder) {
-          final result = builder.importLibraryElement(
-            targetLibrary: resolvedLibrary,
-            targetPath: libraryPath,
-            targetOffset: data.offset,
-            requestedLibrary: requestedLibraryElement,
-            requestedElement: requestedElement,
-          );
+        await builder.addFileEdit(data.file, (builder) {
+          final result = builder.importLibraryElement(library.uri);
           if (result.prefix != null) {
             newInsertText = '${result.prefix}.$newInsertText';
           }

pkg/analysis_server/test/src/domains/completion/get_suggestion_details_test.dart

@@ -87,22 +87,6 @@ main() {} // ref
     _assertEmptyChange(result.change);
   }
 
-  test_invalid_label() async {
-    addTestFile(r'''
-import 'dart:math';
-
-main() {} // ref
-''');
-
-    var mathSet = await waitForSetWithUri('dart:math');
-
-    var response = await waitResponse(
-      _buildRequest(id: mathSet.id, label: 'foo', offset: 0),
-    );
-
-    expect(response.error.code, RequestErrorCode.INVALID_PARAMETER);
-  }
-
   test_invalid_library() async {
     addTestFile('');
 

pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart

@@ -18,15 +18,13 @@ import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart'
     hide Element, ElementKind;
 import 'package:analyzer_plugin/src/utilities/change_builder/change_builder_core.dart';
-import 'package:analyzer_plugin/src/utilities/change_builder/dart/import_library_element.dart';
 import 'package:analyzer_plugin/src/utilities/string_utilities.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_builder_dart.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_workspace.dart';
 import 'package:analyzer_plugin/utilities/range_factory.dart';
 import 'package:charcode/ascii.dart';
 import 'package:dart_style/dart_style.dart';
-import 'package:meta/meta.dart';
 
 /**
  * A [ChangeBuilder] used to build changes in Dart files.
@@ -1291,34 +1289,19 @@ class DartFileEditBuilderImpl extends FileEditBuilderImpl
   }
 
   @override
-  ImportLibraryElementResult importLibraryElement({
-    @required ResolvedLibraryResult targetLibrary,
-    @required String targetPath,
-    @required int targetOffset,
-    @required LibraryElement requestedLibrary,
-    @required Element requestedElement,
-  }) {
-    if (librariesToImport.isNotEmpty ||
-        librariesToRelativelyImport.isNotEmpty) {
-      throw StateError('Only one library can be safely imported.');
+  ImportLibraryElementResult importLibraryElement(Uri uri) {
+    if (resolvedUnit.libraryElement.source.uri == uri) {
+      return ImportLibraryElementResultImpl(null);
     }
 
-    var request = importLibraryElementImpl(
-      targetResolvedLibrary: targetLibrary,
-      targetPath: targetPath,
-      targetOffset: targetOffset,
-      requestedLibrary: requestedLibrary,
-      requestedElement: requestedElement,
-    );
-
-    var prefix = request.prefix;
-    if (request.uri != null) {
-      var uriText = _getLibraryUriText(request.uri);
-      (libraryChangeBuilder ?? this).librariesToImport[request.uri] =
-          _LibraryToImport(uriText, prefix);
+    for (var import in resolvedUnit.libraryElement.imports) {
+      if (import.importedLibrary.source.uri == uri) {
+        return ImportLibraryElementResultImpl(import.prefix?.name);
+      }
     }
 
-    return ImportLibraryElementResultImpl(prefix);
+    importLibrary(uri);
+    return ImportLibraryElementResultImpl(null);
   }
 
   String importLibraryWithRelativeUri(String uriText, [String prefix = null]) {