[CFE] [Language versioning] Issue error on multiple 'dart=' entries

Issue error when the .packages file specifies more than on 'dart=' entry.
Also add another test of the library and part mismatch being an error.

Change-Id: I0a894e6ef86eb9f976b9fbdce67f0c9adb03be9b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/112881
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

pkg/front_end/lib/src/fasta/loader.dart

@@ -126,9 +126,19 @@ abstract class Loader {
       int packageSpecifiedLanguageVersionMinor;
       if (packageFragment != null) {
         List<String> properties = packageFragment.split("&");
+        int foundEntries = 0;
         for (int i = 0; i < properties.length; ++i) {
           String property = properties[i];
           if (property.startsWith("dart=")) {
+            if (++foundEntries > 1) {
+              // Force error to be issued if more than one "dart=" entry.
+              // (The error will be issued in library.setLanguageVersion below
+              // when giving it `null` version numbers.)
+              packageSpecifiedLanguageVersionMajor = null;
+              packageSpecifiedLanguageVersionMinor = null;
+              break;
+            }
+
             hasPackageSpecifiedLanguageVersion = true;
             String langaugeVersionString = property.substring(5);
 
@@ -140,7 +150,6 @@ abstract class Loader {
               packageSpecifiedLanguageVersionMinor =
                   int.tryParse(dotSeparatedParts[1]);
             }
-            break;
           }
         }
       }

pkg/front_end/lib/src/testing/id_testing.dart

@@ -635,6 +635,9 @@ Future runTests(Directory dataDir,
   int testCount = 0;
   for (FileSystemEntity entity in entities) {
     String name = entity.uri.pathSegments.last;
+    if (entity is Directory) {
+      name = entity.uri.pathSegments[entity.uri.pathSegments.length - 2];
+    }
     if (args.isNotEmpty && !args.contains(name) && !continued) continue;
     if (shouldContinue) continued = true;
     testCount++;

pkg/front_end/test/language_versioning/data/package_default_version_is_wrong_3/.packages

@@ -0,0 +1 @@
+foo:lib/#dart=2.5&dart=arglebargle

pkg/front_end/test/language_versioning/data/package_default_version_is_wrong_3/lib/foo.dart

@@ -0,0 +1,13 @@
+/*error: LanguageVersionInvalidInDotPackages*/
+// Copyright (c) 2019, 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: languageVersion=2.8*/
+
+import 'foo2.dart';
+
+foo() {
+  print("Hello from foo!");
+  foo2();
+}

pkg/front_end/test/language_versioning/data/package_default_version_is_wrong_3/lib/foo2.dart

@@ -0,0 +1,12 @@
+/*error: LanguageVersionInvalidInDotPackages*/
+// Copyright (c) 2019, 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.
+
+// @dart = 2.4
+
+/*library: languageVersion=2.4*/
+
+foo2() {
+  print("Hello from foo2!");
+}

pkg/front_end/test/language_versioning/data/package_default_version_is_wrong_3/main.dart

@@ -0,0 +1,16 @@
+// Copyright (c) 2019, 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.
+
+// Set version of this file (not technically in package) explicitly to test as
+// much as possibly separately.
+
+// @dart = 2.4
+
+import 'package:foo/foo.dart';
+
+/*library: languageVersion=2.4*/
+
+main() {
+  foo();
+}

pkg/front_end/test/language_versioning/data/package_default_version_is_wrong_3/pubspec.yaml

@@ -0,0 +1,5 @@
+# Copyright (c) 2019, 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.
+
+# Analyzer workaround, see https://github.com/dart-lang/sdk/issues/37513

pkg/front_end/test/language_versioning/data/parts_disagreeing_has_package_2/.packages

@@ -0,0 +1 @@
+foo:lib/#dart=2.5

pkg/front_end/test/language_versioning/data/parts_disagreeing_has_package_2/lib/foo.dart

@@ -0,0 +1,14 @@
+// Copyright (c) 2019, 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.
+
+// The library and its part is both technically at language version 2.5,
+// but one is explicitly set, the other is not. That's an error.
+
+part /*error: LanguageVersionMismatchInPart*/ 'part.dart';
+
+/*library: languageVersion=2.5*/
+
+foo() {
+  /*error: MethodNotFound*/ bar();
+}

pkg/front_end/test/language_versioning/data/parts_disagreeing_has_package_2/lib/part.dart

@@ -0,0 +1,9 @@
+// Copyright (c) 2019, 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.
+
+// @dart = 2.5
+
+part of 'foo.dart';
+
+bar() {}

pkg/front_end/test/language_versioning/data/parts_disagreeing_has_package_2/main.dart

@@ -0,0 +1,16 @@
+// Copyright (c) 2019, 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.
+
+// Set version of this file (not technically in package) explicitly to test as
+// much as possibly separately.
+
+// @dart = 2.4
+
+import 'package:foo/foo.dart';
+
+/*library: languageVersion=2.4*/
+
+main() {
+  main();
+}

pkg/front_end/test/language_versioning/data/parts_disagreeing_has_package_2/pubspec.yaml

@@ -0,0 +1,5 @@
+# Copyright (c) 2019, 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.
+
+# Analyzer workaround, see https://github.com/dart-lang/sdk/issues/37513