Support for extracting methods with parameters.

R=brianwilkerson@google.com

Bug: https://github.com/flutter/flutter-intellij/issues/1250
Change-Id: I906e14feba246a7704fbbcdaa358730be5916a47
Reviewed-on: https://dart-review.googlesource.com/47945
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analysis_server/lib/src/services/refactoring/extract_widget.dart

@@ -205,11 +205,11 @@ class ExtractWidgetRefactoringImpl extends RefactoringImpl
 
     // We added fields, now add the method parameters.
     if (_method != null) {
-      // TODO(scheglov) test for method parameters
       for (var parameter in _method.parameters.parameters) {
         if (parameter is NormalFormalParameter) {
           _parameters.add(new _Parameter(
-              parameter.identifier.name, parameter.element.type));
+              parameter.identifier.name, parameter.element.type,
+              isMethodParameter: true));
         }
       }
     }
@@ -231,10 +231,29 @@ class ExtractWidgetRefactoringImpl extends RefactoringImpl
     var collector = new _MethodInvocationsCollector(_method.element);
     _enclosingClassNode.accept(collector);
     for (var invocation in collector.invocations) {
-      builder.addReplacement(range.node(invocation), (builder) {
-        // TODO(scheglov) use arguments
-        _writeWidgetInstantiation(builder);
-      });
+      builder.addReplacement(
+        range.startEnd(invocation, invocation.argumentList.leftParenthesis),
+        (builder) {
+          builder.write('new $name(');
+
+          // Insert field references.
+          for (var parameter in _parameters) {
+            if (parameter.isMethodParameter) {
+              break;
+            }
+            if (parameter != _parameters.first) {
+              builder.write(', ');
+            }
+            builder.write(parameter.name);
+          }
+
+          // Separate references to fields and method arguments.
+          if (_parameters.isNotEmpty &&
+              invocation.argumentList.arguments.isNotEmpty) {
+            builder.write(', ');
+          }
+        },
+      );
     }
   }
 
@@ -336,7 +355,10 @@ class _Parameter {
   final String name;
   final DartType type;
 
-  _Parameter(this.name, this.type);
+  /// Whether the parameter is a parameter of the method being extracted.
+  final bool isMethodParameter;
+
+  _Parameter(this.name, this.type, {this.isMethodParameter = false});
 }
 
 class _ParametersCollector extends RecursiveAstVisitor<void> {

pkg/analysis_server/test/services/refactoring/extract_widget_test.dart

@@ -357,6 +357,73 @@ class Test extends StatelessWidget {
 ''');
   }
 
+  test_method_parameters() async {
+    addFlutterPackage();
+    await indexTestUnit(r'''
+import 'package:flutter/material.dart';
+
+class MyWidget extends StatelessWidget {
+  String foo;
+
+  @override
+  Widget build(BuildContext context) {
+    int bar = 1;
+    return new Row(
+      children: <Widget>[
+        createColumn('aaa', bar),
+        createColumn('bbb', 2),
+      ],
+    );
+  }
+  
+  Widget createColumn(String p1, int p2) {
+    var a = new Text('$foo $p1');
+    var b = new Text('$p2');
+    return new Column(
+      children: <Widget>[a, b],
+    );
+  }
+}
+''');
+    _createRefactoringForStringOffset('createColumn(String');
+
+    await _assertSuccessfulRefactoring(r'''
+import 'package:flutter/material.dart';
+
+class MyWidget extends StatelessWidget {
+  String foo;
+
+  @override
+  Widget build(BuildContext context) {
+    int bar = 1;
+    return new Row(
+      children: <Widget>[
+        new Test(foo, 'aaa', bar),
+        new Test(foo, 'bbb', 2),
+      ],
+    );
+  }
+}
+
+class Test extends StatelessWidget {
+  final String foo;
+  final String p1;
+  final int p2;
+
+  Test(this.foo, this.p1, this.p2);
+
+  @override
+  Widget build(BuildContext context) {
+    var a = new Text('$foo $p1');
+    var b = new Text('$p2');
+    return new Column(
+      children: <Widget>[a, b],
+    );
+  }
+}
+''');
+  }
+
   test_parameters_field_read_enclosingClass() async {
     addFlutterPackage();
     await indexTestUnit(r'''