Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/code_transformers/src/resolvers.dart

+// Copyright (c) 2014, 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 code_transformers.src.resolvers;
+
+import 'dart:async';
+import 'package:barback/barback.dart';
+
+import 'package:analyzer/src/generated/engine.dart' show AnalysisOptions;
+import 'package:analyzer/src/generated/sdk.dart' show DartSdk;
+import 'package:analyzer/src/generated/source.dart' show DartUriResolver;
+
+import 'entry_point.dart';
+import 'resolver.dart';
+import 'resolver_impl.dart';
+import 'dart_sdk.dart' hide dartSdkDirectory;
+
+/// Barback-based code resolvers which maintains up-to-date resolved ASTs for
+/// the specified code entry points.
+///
+/// This can used by transformers dependent on resolved ASTs to handle the
+/// resolution of the AST and cache the results between compilations.
+///
+/// If multiple transformers rely on a resolved AST they should (ideally) share
+/// the same Resolvers object to minimize re-parsing the AST.
+class Resolvers {
+  final Map<AssetId, Resolver> _resolvers = {};
+  final DartSdk dartSdk;
+  final DartUriResolver dartUriResolver;
+  final AnalysisOptions options;
+
+  Resolvers.fromSdk(this.dartSdk, this.dartUriResolver, {this.options});
+
+  factory Resolvers(dartSdkDirectory, {AnalysisOptions options}) {
+    var sdk = new DirectoryBasedDartSdkProxy(dartSdkDirectory);
+    var uriResolver = new DartUriResolverProxy(sdk);
+    return new Resolvers.fromSdk(sdk, uriResolver, options: options);
+  }
+
+  factory Resolvers.fromMock(Map<String, String> sources,
+      {bool reportMissing: false, AnalysisOptions options}) {
+    var sdk = new MockDartSdk(sources, reportMissing: reportMissing);
+    return new Resolvers.fromSdk(sdk, sdk.resolver, options: options);
+  }
+
+  /// Get a resolver for [transform]. If provided, this resolves the code
+  /// starting from each of the assets in [entryPoints]. If not, this resolves
+  /// the code starting from `transform.primaryInput.id` by default.
+  ///
+  /// [Resolver.release] must be called once it's done being used, or
+  /// [ResolverTransformer] should be used to automatically release the
+  /// resolver.
+  Future<Resolver> get(Transform transform, [List<AssetId> entryPoints]) {
+    var id = transform.primaryInput.id;
+    var resolver = _resolvers.putIfAbsent(id,
+        () => new ResolverImpl(dartSdk, dartUriResolver, options: options));
+    return resolver.resolve(transform, entryPoints);
+  }
+}
+
+/// Transformer mixin which automatically gets and releases resolvers.
+///
+/// To use mix this class in, set the resolvers field and override
+/// [applyResolver].
+abstract class ResolverTransformer implements Transformer {
+  /// The cache of resolvers- must be set from subclass.
+  Resolvers resolvers;
+
+  /// By default only process prossible entry point assets.
+  ///
+  /// This is only a preliminary check based on the asset ID.
+  Future<bool> isPrimary(assetOrId) {
+    // assetOrId is to handle the transition from Asset to AssetID between
+    // pub 1.3 and 1.4. Once support for 1.3 is dropped this should only
+    // support AssetId.
+    var id = assetOrId is AssetId ? assetOrId : assetOrId.id;
+    return new Future.value(isPossibleDartEntryId(id));
+  }
+
+  /// Check to see if this should apply with the resolver on the provided asset.
+  ///
+  /// By default this will only apply on possible Dart entry points (see
+  /// [isPossibleDartEntry]).
+  Future<bool> shouldApplyResolver(Asset asset) => isPossibleDartEntry(asset);
+
+
+  /// This provides a default implementation of `Transformer.apply` that will
+  /// get and release resolvers automatically. Internally this:
+  ///   * Gets a resolver associated with the transform primary input.
+  ///   * Does resolution to the code starting from that input.
+  ///   * Calls [applyResolver].
+  ///   * Then releases the resolver.
+  ///
+  /// Use [applyToEntryPoints] instead if you need to override the entry points
+  /// to run the resolver on.
+  Future apply(Transform transform) =>
+      shouldApplyResolver(transform.primaryInput).then((result) {
+        if (result) return applyToEntryPoints(transform);
+      });
+
+
+  /// Helper function to make it easy to write an `Transformer.apply` method
+  /// that automatically gets and releases the resolver. This is typically used
+  /// as follows:
+  ///
+  ///    Future apply(Transform transform) {
+  ///       var entryPoints = ...; // compute entry points
+  ///       return applyToEntryPoints(transform, entryPoints);
+  ///    }
+  Future applyToEntryPoints(Transform transform, [List<AssetId> entryPoints]) {
+    return resolvers.get(transform, entryPoints).then((resolver) {
+      return new Future(() => applyResolver(transform, resolver))
+        .whenComplete(() {
+          resolver.release();
+        });
+    });
+  }
+
+  /// Invoked when the resolver is ready to be processed.
+  ///
+  /// Return a Future to indicate when apply is completed.
+  applyResolver(Transform transform, Resolver resolver);
+}