do not suggest completions for cascade on library prefix - fixes #25215

pkg/analysis_server/lib/src/services/completion/dart/library_member_contributor.dart

Index: pkg/analysis_server/lib/src/services/completion/dart/library_member_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/library_member_contributor.dart b/pkg/analysis_server/lib/src/services/completion/dart/library_member_contributor.dart
index bfbbc0b96152876dbe1362272b4c2ca49307c409..d0653c901ab8ec8e6be33ee1f65881d7cda414fe 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/library_member_contributor.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/library_member_contributor.dart
@@ -7,7 +7,6 @@ library services.completion.contributor.dart.library_member;
 import 'dart:async';
 
 import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
-import 'package:analysis_server/src/provisional/completion/dart/completion_target.dart';
 import 'package:analysis_server/src/services/completion/dart/suggestion_builder.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ -23,92 +22,69 @@ class LibraryMemberContributor extends DartCompletionContributor {
   @override
   Future<List<CompletionSuggestion>> computeSuggestions(
       DartCompletionRequest request) async {
-    // Determine if the target looks like a prefixed identifier,
-    // a method invocation, or a property access
-    SimpleIdentifier targetId = _getTargetId(request.target);
-    if (targetId == null) {
+    // Determine if the target looks like a library prefix
+    if (request.dotTarget is! SimpleIdentifier) {
       return EMPTY_LIST;
     }
 
     // Resolve the expression and the containing library
-    await request.resolveExpression(targetId);
-    LibraryElement containingLibrary = await request.libraryElement;
-    List<Directive> directives = await request.resolveDirectives();
-    // Gracefully degrade if the library or directives could not be determined
-    // e.g. detached part file or source change
-    if (containingLibrary == null || directives == null) {
-      return EMPTY_LIST;
-    }
+    await request.resolveExpression(request.dotTarget);
 
     // Recompute the target since resolution may have changed it
-    targetId = _getTargetId(request.target);
-    if (targetId == null) {
-      return EMPTY_LIST;
+    Expression targetId = request.dotTarget;
+    if (targetId is SimpleIdentifier && !request.target.isCascade) {
+      Element elem = targetId.bestElement;
+      if (elem is PrefixElement) {
+        LibraryElement containingLibrary = await request.libraryElement;
+        List<Directive> directives = await request.resolveDirectives();
+        // Gracefully degrade if the library or directives
+        // could not be determined (e.g. detached part file or source change)
+        if (containingLibrary != null && directives != null) {
+          return _buildSuggestions(
+              request, elem, containingLibrary, directives);
+        }
+      }
     }
+    return EMPTY_LIST;
+  }
 
-    // Build the suggestions
-    Element elem = targetId.bestElement;
-    if (elem is PrefixElement) {
-      List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];
+  List<CompletionSuggestion> _buildSuggestions(
+      DartCompletionRequest request,
+      PrefixElement elem,
+      LibraryElement containingLibrary,
+      List<Directive> directives) {
+    List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];
+    for (Directive directive in directives) {
+      if (directive is ImportDirective) {
+        if (directive.prefix != null) {
+          if (directive.prefix.name == elem.name) {
+            LibraryElement library = directive.uriElement;
 
-      // Find the import directive with the given prefix
-      for (Directive directive in directives) {
-        if (directive is ImportDirective) {
-          if (directive.prefix != null) {
-            if (directive.prefix.name == elem.name) {
-              LibraryElement library = directive.uriElement;
-              if (library != null) {
-                // Suggest elements from the imported library
-                AstNode parent = request.target.containingNode.parent;
-                bool isConstructor = parent.parent is ConstructorName;
-                bool typesOnly = parent is TypeName;
-                bool instCreation = typesOnly && isConstructor;
-                LibraryElementSuggestionBuilder builder =
-                    new LibraryElementSuggestionBuilder(
-                        containingLibrary,
-                        CompletionSuggestionKind.INVOCATION,
-                        typesOnly,
-                        instCreation);
-                library.visitChildren(builder);
-                suggestions.addAll(builder.suggestions);
+            // Suggest elements from the imported library
+            if (library != null) {
+              AstNode parent = request.target.containingNode.parent;
+              bool isConstructor = parent.parent is ConstructorName;
+              bool typesOnly = parent is TypeName;
+              bool instCreation = typesOnly && isConstructor;
+              LibraryElementSuggestionBuilder builder =
+                  new LibraryElementSuggestionBuilder(
+                      containingLibrary,
+                      CompletionSuggestionKind.INVOCATION,
+                      typesOnly,
+                      instCreation);
+              library.visitChildren(builder);
+              suggestions.addAll(builder.suggestions);
 
-                // If the import is 'deferred' then suggest 'loadLibrary'
-                if (directive.deferredKeyword != null) {
-                  FunctionElement loadLibFunct = library.loadLibraryFunction;
-                  suggestions.add(createSuggestion(loadLibFunct));
-                }
+              // If the import is 'deferred' then suggest 'loadLibrary'
+              if (directive.deferredKeyword != null) {
+                FunctionElement loadLibFunct = library.loadLibraryFunction;
+                suggestions.add(createSuggestion(loadLibFunct));
               }
             }
           }
         }
       }
-      return suggestions;
-    }
-    return EMPTY_LIST;
-  }
-
-  /**
-   * Return the identifier to the left of the 'dot' or `null` if none.
-   */
-  SimpleIdentifier _getTargetId(CompletionTarget target) {
-    AstNode node = target.containingNode;
-    if (node is MethodInvocation) {
-      if (identical(node.methodName, target.entity)) {
-        Expression target = node.realTarget;
-        if (target is SimpleIdentifier) {
-          return target;
-        }
-      } else {
-        return null;
-      }
-    }
-    if (node is PrefixedIdentifier) {
-      if (identical(node.identifier, target.entity)) {
-        return node.prefix;
-      } else {
-        return null;
-      }
     }
-    return null;
+    return suggestions;
   }
 }