Do nothing if the changed file is not known to the driver.

pkg/analyzer/test/src/dart/analysis/driver_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.driver;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 344 matching lines @@
     {
       AnalysisResult ar = allResults.firstWhere((r) => r.path == a);
       expect(_getTopLevelVarType(ar.unit, 'A'), 'int');
     }
     allResults.clear();
 
     // Change "b" and notify.
     provider.updateFile(b, 'var B = 1.2;');
     driver.changeFile(b);
 
+    // "b" is not an added file, so it is not scheduled for analysis.
+    expect(driver.test.filesToAnalyze, isEmpty);
+
     // While "b" is not analyzed explicitly, it is analyzed implicitly.
     // The change causes "a" to be reanalyzed.
     await _waitForIdle();
     expect(allResults, hasLength(1));
     {
       AnalysisResult ar = allResults.firstWhere((r) => r.path == a);
       expect(_getTopLevelVarType(ar.unit, 'A'), 'double');
     }
   }
 
+  test_changeFile_notUsed() async {
+    var a = _p('/test/lib/a.dart');
+    var b = _p('/other/b.dart');
+    provider.newFile(a, '');
+    provider.newFile(b, 'class B1 {}');
+
+    driver.addFile(a);
+
+    await _waitForIdle();
+    allResults.clear();
+
+    // Change "b" and notify.
+    // Nothing depends on "b", so nothing is analyzed.
+    provider.updateFile(b, 'class B2 {}');
+    driver.changeFile(b);
+    await _waitForIdle();
+    expect(allResults, isEmpty);
+
+    // This should not add "b" to the file state.
+    expect(driver.fsState.knownFilePaths, isNot(contains(b)));
+  }
+
   test_changeFile_selfConsistent() async {
     var a = _p('/test/lib/a.dart');
     var b = _p('/test/lib/b.dart');
     provider.newFile(
         a,
         r'''
 import 'b.dart';
 var A1 = 1;
 var A2 = B1;
 ''');
@@ skipping 63 matching lines @@
     allResults.clear();
     provider.updateFile(testFile, 'var V = 1.2');
 
     // No new results.
     await pumpEventQueue();
     expect(allResults, isEmpty);
 
     // Notify the driver about the change.
     driver.changeFile(testFile);
 
+    // The file was added, so it is scheduled for analysis.
+    expect(driver.test.filesToAnalyze, contains(testFile));
+
     // We get a new result.
     {
       await _waitForIdle();
       expect(allResults, hasLength(1));
       AnalysisResult result = allResults[0];
       expect(result.path, testFile);
       expect(_getTopLevelVarType(result.unit, 'V'), 'double');
     }
   }
 
@@ skipping 1183 matching lines @@
   String _p(String path) => provider.convertPath(path);
 
   Future<Null> _waitForIdle() async {
     await idleStatusMonitor.signal;
   }
 
   static String _md5(String content) {
     return hex.encode(md5.convert(UTF8.encode(content)).bytes);
   }
 }