Use declared variables to select the correct configuration for resolution

pkg/analyzer/test/src/task/dart_test.dart

Index: pkg/analyzer/test/src/task/dart_test.dart
diff --git a/pkg/analyzer/test/src/task/dart_test.dart b/pkg/analyzer/test/src/task/dart_test.dart
index 951ee79779aa39a329cbe8480c6ca1ed8d8653bf..a95d933015c97bc3da152204503062e17057a624 100644
--- a/pkg/analyzer/test/src/task/dart_test.dart
+++ b/pkg/analyzer/test/src/task/dart_test.dart
@@ -3238,6 +3238,108 @@ class A {''');
     expect(outputs[UNITS], hasLength(2));
   }
 
+  test_perform_library_configurations_bool1() {
+    context.declaredVariables.define('dart.library.io', 'true');
+    newSource('/foo.dart', '');
+    newSource('/foo_io.dart', '');
+    newSource('/foo_html.dart', '');
+    newSource('/bar.dart', '');
+    newSource('/bar_io.dart', '');
+    newSource('/bar_html.dart', '');
+    _performParseTask(r'''
+import 'foo.dart'
+  if (dart.library.io) 'foo_io.dart'
+  if (dart.library.html) 'foo_html.dart';
+export 'bar.dart'
+  if (dart.library.io) 'bar_io.dart'
+  if (dart.library.html) 'bar_html.dart';
+''');
+    var unit = outputs[PARSED_UNIT] as CompilationUnit;
+
+    var imported = outputs[IMPORTED_LIBRARIES] as List<Source>;
+    _assertContainsOnlyShortName(imported, 'foo_io.dart');
+
+    var import = unit.directives[0] as ImportDirective;
+    expect(import.uriSource.shortName, 'foo.dart');
+    expect(import.selectedSource.shortName, 'foo_io.dart');
+    expect(import.configurations[0].uriSource.shortName, 'foo_io.dart');
+    expect(import.configurations[1].uriSource.shortName, 'foo_html.dart');
+
+    var exported = outputs[EXPORTED_LIBRARIES] as List<Source>;
+    _assertContainsOnlyShortName(exported, 'bar_io.dart');
+
+    var export = unit.directives[1] as ExportDirective;
+    expect(export.uriSource.shortName, 'bar.dart');
+    expect(export.selectedSource.shortName, 'bar_io.dart');
+    expect(export.configurations[0].uriSource.shortName, 'bar_io.dart');
+    expect(export.configurations[1].uriSource.shortName, 'bar_html.dart');
+  }
+
+  test_perform_library_configurations_bool2() {
+    context.declaredVariables.define('dart.library.html', 'true');
+    newSource('/foo.dart', '');
+    newSource('/foo_io.dart', '');
+    newSource('/foo_html.dart', '');
+    _performParseTask(r'''
+import 'foo.dart'
+  if (dart.library.io) 'foo_io.dart'
+  if (dart.library.html) 'foo_html.dart';
+''');
+    var imported = outputs[IMPORTED_LIBRARIES] as List<Source>;
+    _assertContainsOnlyShortName(imported, 'foo_html.dart');
+  }
+
+  test_perform_library_configurations_default() {
+    context.declaredVariables.define('dart.library.io', 'false');
+    newSource('/foo.dart', '');
+    newSource('/foo_io.dart', '');
+    newSource('/foo_html.dart', '');
+    _performParseTask(r'''
+import 'foo.dart'
+  if (dart.library.io) 'foo_io.dart'
+  if (dart.library.html) 'foo_html.dart';
+''');
+    var imported = outputs[IMPORTED_LIBRARIES] as List<Source>;
+    _assertContainsOnlyShortName(imported, 'foo.dart');
+  }
+
+  test_perform_library_configurations_preferFirst() {
+    context.declaredVariables.define('dart.library.io', 'true');
+    context.declaredVariables.define('dart.library.html', 'true');
+    newSource('/foo.dart', '');
+    newSource('/foo_io.dart', '');
+    newSource('/foo_html.dart', '');
+    _performParseTask(r'''
+import 'foo.dart'
+  if (dart.library.io) 'foo_io.dart'
+  if (dart.library.html) 'foo_html.dart';
+''');
+
+    var imported = outputs[IMPORTED_LIBRARIES] as List<Source>;
+    _assertContainsOnlyShortName(imported, 'foo_io.dart');
+
+    var unit = outputs[PARSED_UNIT] as CompilationUnit;
+    var import = unit.directives[0] as ImportDirective;
+    expect(import.uriSource.shortName, 'foo.dart');
+    expect(import.selectedSource.shortName, 'foo_io.dart');
+    expect(import.configurations[0].uriSource.shortName, 'foo_io.dart');
+    expect(import.configurations[1].uriSource.shortName, 'foo_html.dart');
+  }
+
+  test_perform_library_configurations_value() {
+    context.declaredVariables.define('dart.platform', 'Windows');
+    newSource('/foo.dart', '');
+    newSource('/foo_posix.dart', '');
+    newSource('/foo_windows.dart', '');
+    _performParseTask(r'''
+import 'foo.dart'
+  if (dart.platform == 'Posix') 'foo_posix.dart'
+  if (dart.platform == 'Windows') 'foo_windows.dart';
+''');
+    var imported = outputs[IMPORTED_LIBRARIES] as List<Source>;
+    _assertContainsOnlyShortName(imported, 'foo_windows.dart');
+  }
+
   test_perform_library_selfReferenceAsPart() {
     _performParseTask(r'''
 library lib;
@@ -3264,6 +3366,20 @@ class B {}''');
     expect(outputs[UNITS], hasLength(1));
   }
 
+  /**
+   * Assert that [sources] contains either just a source with the given
+   * [expectedShortName], or it and the `dart:core` source.
+   */
+  void _assertContainsOnlyShortName(
+      List<Source> sources, String expectedShortName) {
+    Iterable<String> shortNames = sources.map((s) => s.shortName);
+    if (shortNames.length == 2) {
+      expect(shortNames, unorderedEquals(['core.dart', expectedShortName]));
+    } else {
+      expect(shortNames, unorderedEquals([expectedShortName]));
+    }
+  }
+
   void _performParseTask(String content) {
     if (content == null) {
       source = resourceProvider.getFile('/test.dart').createSource();