Add version validation for LookupMap, also add unittest directly in LookupMap (take 2)

pkg/compiler/lib/src/js_backend/lookup_map_analysis.dart

 // Copyright (c) 2015, 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.
 
 /// Analysis to determine how to generate code for `LookupMap`s.
 library compiler.src.js_backend.lookup_map_analysis;
 
 import '../common/registry.dart' show Registry;
 import '../compiler.dart' show Compiler;
+import '../diagnostics/messages.dart' show MessageKind;
 import '../constants/values.dart' show
      ConstantValue,
      ConstructedConstantValue,
      ListConstantValue,
      NullConstantValue,
      TypeConstantValue;
 import '../dart_types.dart' show DartType;
-import '../elements/elements.dart' show Elements, Element, ClassElement,
-     FieldElement, FunctionElement, FunctionSignature;
+import '../elements/elements.dart' show
+    ClassElement,
+    Element,
+    Elements,
+    FieldElement,
+    FunctionElement,
+    FunctionSignature,
+    LibraryElement,
+    VariableElement;
 import '../enqueue.dart' show Enqueuer;
 import 'js_backend.dart' show JavaScriptBackend;
 import '../dart_types.dart' show DynamicType, InterfaceType;
 
 /// An analysis and optimization to remove unused entries from a `LookupMap`.
 ///
 /// `LookupMaps` are defined in `package:lookup_map/lookup_map.dart`. They are
 /// simple maps that contain constant expressions as keys, and that only support
 /// the lookup operation.
 ///
@@ skipping 27 matching lines @@
 // TODO(sigmund): add support for const expressions, currently this
 // implementation only supports Type literals. To support const expressions we
 // need to change some of the invariants below (e.g. we can no longer use the
 // ClassElement of a type to refer to keys we need to discover).
 // TODO(sigmund): detect uses of mirrors
 class LookupMapAnalysis {
   /// Reference to [JavaScriptBackend] to be able to enqueue work when we
   /// discover that a key in a map is potentially used.
   final JavaScriptBackend backend;
 
+  /// The resolved [VariableElement] associated with the top-level `_version`.
+  VariableElement lookupMapVersionVariable;
+
+  /// The resolved [LibraryElement] associated with
+  /// `package:lookup_map/lookup_map.dart`.
+  LibraryElement lookupMapLibrary;
+
   /// The resolved [ClassElement] associated with `LookupMap`.
   ClassElement typeLookupMapClass;
 
   /// The resolved [FieldElement] for `LookupMap._entries`.
   FieldElement entriesField;
 
   /// The resolved [FieldElement] for `LookupMap._key`.
   FieldElement keyField;
 
   /// The resolved [FieldElement] for `LookupMap._value`.
@@ skipping 18 matching lines @@
   /// we could allow const instances of these types.  However, we internally use
   /// a hash map within lookup-maps today, so we need this restriction.
   final _typesWithEquals = <ClassElement, bool>{};
 
   /// Pending work to do if we discover that a new key is in use. For each key
   /// that we haven't seen, we record the list of lookup-maps that contain an
   /// entry with that key.
   final _pending = <ConstantValue, List<_LookupMapInfo>>{};
 
   /// Whether the backend is currently processing the codegen queue.
-  // TODO(sigmund): is there a better way to do this. Do we need to plumb the
-  // enqueuer on each callback?
-  bool get _inCodegen => backend.compiler.phase == Compiler.PHASE_COMPILING;
+  bool _inCodegen = false;
 
   LookupMapAnalysis(this.backend);
 
   /// Whether this analysis and optimization is enabled.
   bool get _isEnabled {
     // `lookupMap==off` kept here to make it easy to test disabling this feature
     if (const String.fromEnvironment('lookupMap') == 'off') return false;
     return typeLookupMapClass != null;
   }
 
-  /// Initializes this analysis by providing the resolver information of
-  /// `LookupMap`.
-  void initRuntimeClass(ClassElement cls) {
+  /// Initializes this analysis by providing the resolved library. This is
+  /// invoked during resolution when the `lookup_map` library is discovered.
+  void init(LibraryElement library) {
+    lookupMapLibrary = library;
+    // We will enable the lookupMapAnalysis as long as we get a known version of
+    // the lookup_map package. We otherwise produce a warning.
+    lookupMapVersionVariable = library.implementation.findLocal('_version');
+    if (lookupMapVersionVariable == null) {
+      backend.compiler.reportInfo(library,
+          MessageKind.UNRECOGNIZED_VERSION_OF_LOOKUP_MAP);
+    } else {
+      backend.compiler.enqueuer.resolution.addToWorkList(
+          lookupMapVersionVariable);
+    }
+  }
+
+  /// Checks if the version of lookup_map is valid, and if so, enable this
+  /// analysis during codegen.
+  void onCodegenStart() {
+    _inCodegen = true;
+    if (lookupMapVersionVariable == null) return;
+
+    // At this point, the lookupMapVersionVariable should be resolved and it's
+    // constant value should be available.
+    ConstantValue value =
+        backend.constants.getConstantValueForVariable(lookupMapVersionVariable);
+    if (value == null) {
+      backend.compiler.reportInfo(lookupMapVersionVariable,
+          MessageKind.UNRECOGNIZED_VERSION_OF_LOOKUP_MAP);
+      return;
+    }
+
+    // TODO(sigmund): add proper version resolution using the pub_semver package
+    // when we introduce the next version.
+    String version = value.primitiveValue.slowToString();
+    if (version != '0.0.1') {
+      backend.compiler.reportInfo(lookupMapVersionVariable,
+          MessageKind.UNRECOGNIZED_VERSION_OF_LOOKUP_MAP);
+      return;
+    }
+
+    ClassElement cls = lookupMapLibrary.findLocal('LookupMap');
     cls.computeType(backend.compiler);
     entriesField = cls.lookupMember('_entries');
     keyField = cls.lookupMember('_key');
     valueField = cls.lookupMember('_value');
-    // TODO(sigmund): Maybe inline nested maps make the output code smaller?
+    // TODO(sigmund): Maybe inline nested maps to make the output code smaller?
     typeLookupMapClass = cls;
   }
 
   /// Whether [constant] is an instance of a `LookupMap`.
   bool isLookupMap(ConstantValue constant) =>
       _isEnabled &&
       constant is ConstructedConstantValue &&
       constant.type.asRaw().element.isSubclassOf(typeLookupMapClass);
 
   /// Registers an instance of a lookup-map with the analysis.
@@ skipping 235 matching lines @@
       if (keyValuePairs.length == 2) {
         original.fields[analysis.keyField] = keyValuePairs[0];
         original.fields[analysis.valueField] = keyValuePairs[1];
       }
     } else {
       original.fields[analysis.entriesField] =
           new ListConstantValue(listType, keyValuePairs);
     }
   }
 }