move extractDefinedVariables from analyzer cli to analyzer

pkg/analyzer/test/src/command_line/arguments_test.dart

 // Copyright (c) 2016, 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.
 
 library analyzer.test.src.context.context_builder_test;
 
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/command_line/arguments.dart';
 import 'package:analyzer/src/context/builder.dart';
 import 'package:analyzer/src/dart/sdk/sdk.dart';
@@ skipping 124 matching lines @@
     expect(manager.defaultSdkDirectory, 'y');
     expect(manager.canUseSummaries, true);
   }
 
   void test_defineAnalysisArguments() {
     ArgParser parser = new ArgParser();
     defineAnalysisArguments(parser);
     expect(parser.options, hasLength(12));
   }
 
+  void test_extractDefinedVariables() {
+    List<String> args = ['--a', '-Dbaz', 'go', 'back=blue', '-Dx'];
+    Map<String, String> definedVariables = {'one': 'two'};
+    args = extractDefinedVariables(args, definedVariables);
+    expect(args, orderedEquals(['--a', 'back=blue', '-Dx']));
+    expect(definedVariables['one'], 'two');
+    expect(definedVariables['two'], isNull);
+    expect(definedVariables['baz'], 'go');
+    expect(definedVariables['go'], isNull);
+    expect(definedVariables, hasLength(2));
+  }
+
   void test_filterUnknownArguments() {
     List<String> args = ['--a', '--b', '--c', 'foo', 'bar'];
     ArgParser parser = new ArgParser();
     parser.addFlag('a');
     parser.addFlag('c');
     List<String> result = filterUnknownArguments(args, parser);
     expect(result, orderedEquals(['--a', '--c', 'foo', 'bar']));
   }
 
   void test_parse_noReplacement_noIgnored() {
@@ skipping 48 matching lines @@
   }
 
   void test_preprocessArgs_replacement_notLast() {
     MemoryResourceProvider provider = new MemoryResourceProvider();
     String filePath = provider.convertPath('/args.txt');
     List<String> args = ['a', '@$filePath', 'b'];
     List<String> result = preprocessArgs(provider, args);
     expect(result, orderedEquals(args));
   }
 }