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/file_system/physical_file_system.dart';
import 'package:analyzer/src/generated/engine.dart' show AnalysisOptions;
import 'package:analyzer/src/generated/sdk.dart' show DartSdk;
import 'package:analyzer/src/generated/engine.dart';
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 Resolver _resolver;

  Resolvers.fromSdk(DartSdk dartSdk, DartUriResolver dartUriResolver,
      {AnalysisOptions options})
      : _resolver =
            new ResolverImpl(dartSdk, dartUriResolver, options: options);

  factory Resolvers(String dartSdkDirectory, {AnalysisOptions options}) {
    _initAnalysisEngine();
    var sdk = new FolderBasedDartSdkProxy(
        PhysicalResourceProvider.INSTANCE, 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}) {
    _initAnalysisEngine();
    var sdk = new MockDartSdk(sources, options, 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.
  ///
  /// See [Resolver#resolve] for more info on the `resolveAllLibraries` option.
  Future<Resolver> get(Transform transform,
          [List<AssetId> entryPoints, bool resolveAllLibraries]) =>
      _resolver.resolve(transform, entryPoints, resolveAllLibraries);
}

/// 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;

  /// See [Resolver#resolve] for more info - can be overridden by a subclass.
  bool get resolveAllLibraries => true;

  /// By default only process possible 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 as Asset).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, resolveAllLibraries)
        .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);
}

bool _analysisEngineInitialized = false;
_initAnalysisEngine() {
  if (_analysisEngineInitialized) return;
  _analysisEngineInitialized = true;
  AnalysisEngine.instance.processRequiredPlugins();
}