Add completion support for plugins

pkg/analyzer_plugin/lib/src/utilities/completion.dart

Index: pkg/analyzer_plugin/lib/src/utilities/completion.dart
diff --git a/pkg/analyzer_plugin/lib/src/utilities/completion.dart b/pkg/analyzer_plugin/lib/src/utilities/completion.dart
new file mode 100644
index 0000000000000000000000000000000000000000..341b289cd43ee32e298b08dbceb0154c71f3517b
--- /dev/null
+++ b/pkg/analyzer_plugin/lib/src/utilities/completion.dart
@@ -0,0 +1,72 @@
+// Copyright (c) 2017, 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.
+
+import 'package:analyzer/dart/analysis/results.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart';
+import 'package:analyzer_plugin/utilities/completion.dart';
+
+/**
+ * An object that can collect completion suggestions.
+ */
+class CompletionCollectorImpl implements CompletionCollector {
+  @override
+  int length;
+
+  @override
+  int offset;
+
+  /**
+   * A list of the completion suggestions that have been collected.
+   */
+  List<CompletionSuggestion> suggestions;
+
+  /**
+   * Initialize a newly created completion collector.
+   */
+  CompletionCollectorImpl();
+
+  @override
+  void addSuggestion(CompletionSuggestion suggestion) {
+    suggestions.add(suggestion);
+  }
+}
+
+/**
+ * Information about the completion request that was made.
+ */
+class CompletionRequestImpl implements CompletionRequest {
+  @override
+  final int offset;
+
+  @override
+  final ResourceProvider resourceProvider;
+
+  @override
+  final ResolveResult result;

[mfairhurst, 2017/05/31 21:49:34]

I mentioned this elsewhere in an email, this `result` field isn't useful to us
if its of type `ResolveResult`.

[Brian Wilkerson, 2017/05/31 22:51:47]

Actually, you need this field because it's needed by the other contributors
you're using. The question, I think, is how to allow you to pass along the data
you also need in your contributor.

[mfairhurst, 2017/05/31 23:17:36]

Strictly speaking, I don't think either use this field. It seems to me like in
an ideal world, I should be able to provide an AST node, or a ClassElement, to
an instance of the right class in order to get the references, and not have to
pass in something as heavy duty as a ResolveResult. We've had similar issues
before, where we needed to autocomplete a AST snippet with no CompilationUnit,
and therefore couldn't use the API even though the contributor never used the
CompilationUnit.

+
+  /**
+   * A flag indicating whether completion has been aborted.
+   */
+  bool _aborted = false;
+
+  /**
+   * Initialize a newly created request.
+   */
+  CompletionRequestImpl(this.resourceProvider, this.result, this.offset);
+
+  /**
+   * Abort the current completion request.
+   */
+  void abort() {
+    _aborted = true;
+  }
+
+  @override
+  void checkAborted() {
+    if (_aborted) {
+      throw new AbortCompletion();
+    }
+  }
+}