Extension point for WorkManagerFactory(s).

I'm not quite happy that internal classes get into the extension point declaration.
But I guess that because of the nature of the work WorkManager(s) are doing, we have to have significant exposure to internals.

Also, onAnalysisOptionsChanged() and onSourceFactoryChanged()... these probably are better to implement as streams in InternalAnalysisContext.
Thoughts?

R=brianwilkerson@google.com, paulberry@google.com
BUG=

Review URL: https://codereview.chromium.org//1311773005 .

pkg/analyzer/lib/plugin/task.dart

@@ -8,6 +8,7 @@
  */
 library analyzer.plugin.task;
 
+import 'package:analyzer/src/generated/engine.dart' hide WorkManager;
 import 'package:analyzer/src/plugin/engine_plugin.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:plugin/plugin.dart';
@@ -19,3 +20,17 @@ import 'package:plugin/plugin.dart';
  */
 final String TASK_EXTENSION_POINT_ID = Plugin.join(
     EnginePlugin.UNIQUE_IDENTIFIER, EnginePlugin.TASK_EXTENSION_POINT);
+
+/**
+ * The identifier of the extension point that allows plugins to register new
+ * work managers with the analysis engine. The object used as an extension must
+ * be a [WorkManagerFactory].
+ */
+final String WORK_MANAGER_EXTENSION_POINT_ID = Plugin.join(
+    EnginePlugin.UNIQUE_IDENTIFIER,
+    EnginePlugin.WORK_MANAGER_FACTORY_EXTENSION_POINT);
+
+/**
+ * A function that will create a new [WorkManager] for the given [context].
+ */
+typedef WorkManager WorkManagerFactory(InternalAnalysisContext context);

pkg/analyzer/lib/src/context/cache.dart

@@ -12,7 +12,6 @@ import 'package:analyzer/src/generated/engine.dart'
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/utilities_collection.dart';
-import 'package:analyzer/src/generated/utilities_general.dart';
 import 'package:analyzer/src/task/model.dart';
 import 'package:analyzer/task/model.dart';
 
@@ -1116,46 +1115,6 @@ class SdkCachePartition extends CachePartition {
   }
 }
 
-/**
- * A specification of a specific result computed for a specific target.
- */
-class TargetedResult {
-  /**
-   * An empty list of results.
-   */
-  static final List<TargetedResult> EMPTY_LIST = const <TargetedResult>[];
-
-  /**
-   * The target with which the result is associated.
-   */
-  final AnalysisTarget target;
-
-  /**
-   * The result associated with the target.
-   */
-  final ResultDescriptor result;
-
-  /**
-   * Initialize a new targeted result.
-   */
-  TargetedResult(this.target, this.result);
-
-  @override
-  int get hashCode {
-    return JenkinsSmiHash.combine(target.hashCode, result.hashCode);
-  }
-
-  @override
-  bool operator ==(other) {
-    return other is TargetedResult &&
-        other.target == target &&
-        other.result == result;
-  }
-
-  @override
-  String toString() => '$result for $target';
-}
-
 /**
  * A cache partition that contains all targets not contained in other partitions.
  */

pkg/analyzer/lib/src/context/context.dart

@@ -8,6 +8,7 @@ import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/instrumentation/instrumentation.dart';
+import 'package:analyzer/plugin/task.dart';
 import 'package:analyzer/src/cancelable_future.dart';
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/ast.dart';
@@ -33,8 +34,6 @@ import 'package:analyzer/src/generated/utilities_collection.dart';
 import 'package:analyzer/src/task/dart.dart';
 import 'package:analyzer/src/task/dart_work_manager.dart';
 import 'package:analyzer/src/task/driver.dart';
-import 'package:analyzer/src/task/html.dart';
-import 'package:analyzer/src/task/html_work_manager.dart';
 import 'package:analyzer/src/task/incremental_element_builder.dart';
 import 'package:analyzer/src/task/manager.dart';
 import 'package:analyzer/task/dart.dart';
@@ -121,16 +120,16 @@ class AnalysisContextImpl implements InternalAnalysisContext {
    */
   TaskManager _taskManager;
 
+  /**
+   * A list of all [WorkManager]s used by this context.
+   */
+  final List<WorkManager> workManagers = <WorkManager>[];
+
   /**
    * The [DartWorkManager] instance that performs Dart specific scheduling.
    */
   DartWorkManager dartWorkManager;
 
-  /**
-   * The work manager that performs HTML specific scheduling.
-   */
-  HtmlWorkManager htmlWorkManager;
-
   /**
    * The analysis driver used to perform analysis.
    */
@@ -219,11 +218,17 @@ class AnalysisContextImpl implements InternalAnalysisContext {
     _privatePartition = new UniversalCachePartition(this);
     _cache = createCacheFromSourceFactory(null);
     _taskManager = AnalysisEngine.instance.taskManager;
-    // TODO(scheglov) Get WorkManager(Factory)(s) from plugins.
-    dartWorkManager = new DartWorkManager(this);
-    htmlWorkManager = new HtmlWorkManager(this);
-    driver = new AnalysisDriver(
-        _taskManager, <WorkManager>[dartWorkManager, htmlWorkManager], this);
+    for (WorkManagerFactory factory
+        in AnalysisEngine.instance.enginePlugin.workManagerFactories) {
+      WorkManager workManager = factory(this);
+      if (workManager != null) {
+        workManagers.add(workManager);
+        if (workManager is DartWorkManager) {
+          dartWorkManager = workManager;
+        }
+      }
+    }
+    driver = new AnalysisDriver(_taskManager, workManagers, this);
     _onSourcesChangedController =
         new StreamController<SourcesChangedEvent>.broadcast();
     _implicitAnalysisEventsController =
@@ -268,8 +273,9 @@ class AnalysisContextImpl implements InternalAnalysisContext {
     this._options.lint = options.lint;
     this._options.preserveComments = options.preserveComments;
     if (needsRecompute) {
-      dartWorkManager.onAnalysisOptionsChanged();
-      htmlWorkManager.onAnalysisOptionsChanged();
+      for (WorkManager workManager in workManagers) {
+        workManager.onAnalysisOptionsChanged();
+      }
     }
   }
 
@@ -287,8 +293,9 @@ class AnalysisContextImpl implements InternalAnalysisContext {
         _priorityOrder = sources;
       }
     }
-    dartWorkManager.applyPriorityTargets(_priorityOrder);
-    htmlWorkManager.applyPriorityTargets(_priorityOrder);
+    for (WorkManager workManager in workManagers) {
+      workManager.applyPriorityTargets(_priorityOrder);
+    }
   }
 
   @override
@@ -360,7 +367,8 @@ class AnalysisContextImpl implements InternalAnalysisContext {
   /**
    * Make _pendingFutureSources available to unit tests.
    */
-  HashMap<AnalysisTarget, List<PendingFuture>> get pendingFutureSources_forTesting =>
+  HashMap<AnalysisTarget,
+      List<PendingFuture>> get pendingFutureSources_forTesting =>
       _pendingFutureTargets;
 
   @override
@@ -389,8 +397,9 @@ class AnalysisContextImpl implements InternalAnalysisContext {
     factory.context = this;
     _sourceFactory = factory;
     _cache = createCacheFromSourceFactory(factory);
-    dartWorkManager.onSourceFactoryChanged();
-    htmlWorkManager.onSourceFactoryChanged();
+    for (WorkManager workManager in workManagers) {
+      workManager.onSourceFactoryChanged();
+    }
   }
 
   @override
@@ -531,10 +540,10 @@ class AnalysisContextImpl implements InternalAnalysisContext {
     for (Source source in removedSources) {
       _sourceRemoved(source);
     }
-    dartWorkManager.applyChange(
-        changeSet.addedSources, changeSet.changedSources, removedSources);
-    htmlWorkManager.applyChange(
-        changeSet.addedSources, changeSet.changedSources, removedSources);
+    for (WorkManager workManager in workManagers) {
+      workManager.applyChange(
+          changeSet.addedSources, changeSet.changedSources, removedSources);
+    }
     _onSourcesChangedController.add(new SourcesChangedEvent(changeSet));
   }
 
@@ -635,8 +644,8 @@ class AnalysisContextImpl implements InternalAnalysisContext {
       return new CancelableFuture.error(new AnalysisNotScheduledError());
     }
     var unitTarget = new LibrarySpecificUnit(librarySource, unitSource);
-    return new _AnalysisFutureHelper<CompilationUnit>(this).computeAsync(
-        unitTarget, (CacheEntry entry) {
+    return new _AnalysisFutureHelper<CompilationUnit>(this)
+        .computeAsync(unitTarget, (CacheEntry entry) {
       CacheState state = entry.getState(RESOLVED_UNIT);
       if (state == CacheState.ERROR) {
         throw entry.exception;
@@ -801,13 +810,13 @@ class AnalysisContextImpl implements InternalAnalysisContext {
 
   @override
   AnalysisErrorInfo getErrors(Source source) {
-    String name = source.shortName;
-    if (AnalysisEngine.isDartFileName(name) || source is DartScript) {
-      return dartWorkManager.getErrors(source);
-    } else if (AnalysisEngine.isHtmlFileName(name)) {
-      return htmlWorkManager.getErrors(source);
+    List<AnalysisError> allErrors = <AnalysisError>[];
+    for (WorkManager workManager in workManagers) {
+      List<AnalysisError> errors = workManager.getErrors(source);
+      allErrors.addAll(errors);
     }
-    return new AnalysisErrorInfoImpl(AnalysisError.NO_ERRORS, null);
+    LineInfo lineInfo = getLineInfo(source);
+    return new AnalysisErrorInfoImpl(allErrors, lineInfo);
   }
 
   @override
@@ -1530,8 +1539,12 @@ class AnalysisContextImpl implements InternalAnalysisContext {
    * related to it. If so, add the source to the set of sources that need to be
    * processed. This method is intended to be used for testing purposes only.
    */
-  void _getSourcesNeedingProcessing(Source source, CacheEntry entry,
-      bool isPriority, bool hintsEnabled, bool lintsEnabled,
+  void _getSourcesNeedingProcessing(
+      Source source,
+      CacheEntry entry,
+      bool isPriority,
+      bool hintsEnabled,
+      bool lintsEnabled,
       HashSet<Source> sources) {
     CacheState state = entry.getState(CONTENT);
     if (state == CacheState.INVALID ||
@@ -1763,10 +1776,10 @@ class AnalysisContextImpl implements InternalAnalysisContext {
       }
       entry.setState(CONTENT, CacheState.INVALID);
     }
-    dartWorkManager.applyChange(
-        Source.EMPTY_LIST, <Source>[source], Source.EMPTY_LIST);
-    htmlWorkManager.applyChange(
-        Source.EMPTY_LIST, <Source>[source], Source.EMPTY_LIST);
+    for (WorkManager workManager in workManagers) {
+      workManager.applyChange(
+          Source.EMPTY_LIST, <Source>[source], Source.EMPTY_LIST);
+    }
   }
 
   /**
@@ -1846,11 +1859,18 @@ class AnalysisContextImpl implements InternalAnalysisContext {
       // do resolution
       Stopwatch perfCounter = new Stopwatch()..start();
       PoorMansIncrementalResolver resolver = new PoorMansIncrementalResolver(
-          typeProvider, unitSource, null, sourceEntry, unitEntry, oldUnit,
-          analysisOptions.incrementalApi, analysisOptions);
+          typeProvider,
+          unitSource,
+          null,
+          sourceEntry,
+          unitEntry,
+          oldUnit,
+          analysisOptions.incrementalApi,
+          analysisOptions);
       bool success = resolver.resolve(newCode);
       AnalysisEngine.instance.instrumentationService.logPerformance(
-          AnalysisPerformanceKind.INCREMENTAL, perfCounter,
+          AnalysisPerformanceKind.INCREMENTAL,
+          perfCounter,
           'success=$success,context_id=$_id,code_length=${newCode.length}');
       if (!success) {
         return false;

pkg/analyzer/lib/src/generated/incremental_resolver.dart

@@ -24,7 +24,7 @@ import 'package:analyzer/src/task/dart.dart'
 import 'package:analyzer/task/dart.dart'
     show DART_ERRORS, LibrarySpecificUnit, PARSED_UNIT, TOKEN_STREAM;
 import 'package:analyzer/task/general.dart' show CONTENT, LINE_INFO;
-import 'package:analyzer/task/model.dart' show ResultDescriptor;
+import 'package:analyzer/task/model.dart' show ResultDescriptor, TargetedResult;
 
 import 'ast.dart';
 import 'element.dart';

pkg/analyzer/lib/src/plugin/engine_plugin.dart

@@ -5,9 +5,13 @@
 library analyzer.src.plugin.engine_plugin;
 
 import 'package:analyzer/plugin/task.dart';
+import 'package:analyzer/src/generated/engine.dart'
+    show InternalAnalysisContext;
 import 'package:analyzer/src/task/dart.dart';
+import 'package:analyzer/src/task/dart_work_manager.dart';
 import 'package:analyzer/src/task/general.dart';
 import 'package:analyzer/src/task/html.dart';
+import 'package:analyzer/src/task/html_work_manager.dart';
 import 'package:analyzer/task/model.dart';
 import 'package:plugin/plugin.dart';
 
@@ -22,6 +26,13 @@ class EnginePlugin implements Plugin {
    */
   static const String TASK_EXTENSION_POINT = 'task';
 
+  /**
+   * The simple identifier of the extension point that allows plugins to
+   * register new work manager factories with the analysis engine.
+   */
+  static const String WORK_MANAGER_FACTORY_EXTENSION_POINT =
+      'workManagerFactory';
+
   /**
    * The unique identifier of this plugin.
    */
@@ -33,6 +44,12 @@ class EnginePlugin implements Plugin {
    */
   ExtensionPoint taskExtensionPoint;
 
+  /**
+   * The extension point that allows plugins to register new work manager
+   * factories with the analysis engine.
+   */
+  ExtensionPoint workManagerFactoryExtensionPoint;
+
   /**
    * Initialize a newly created plugin.
    */
@@ -46,14 +63,29 @@ class EnginePlugin implements Plugin {
   @override
   String get uniqueIdentifier => UNIQUE_IDENTIFIER;
 
+  /**
+   * Return a list containing all of the work manager factories that were
+   * contributed.
+   */
+  List<WorkManagerFactory> get workManagerFactories =>
+      workManagerFactoryExtensionPoint.extensions;
+
   @override
   void registerExtensionPoints(RegisterExtensionPoint registerExtensionPoint) {
     taskExtensionPoint =
         registerExtensionPoint(TASK_EXTENSION_POINT, _validateTaskExtension);
+    workManagerFactoryExtensionPoint = registerExtensionPoint(
+        WORK_MANAGER_FACTORY_EXTENSION_POINT,
+        _validateWorkManagerFactoryExtension);
   }
 
   @override
   void registerExtensions(RegisterExtension registerExtension) {
+    _registerTaskExtensions(registerExtension);
+    _registerWorkManagerFactoryExtensions(registerExtension);
+  }
+
+  void _registerTaskExtensions(RegisterExtension registerExtension) {
     String taskId = TASK_EXTENSION_POINT_ID;
     //
     // Register general tasks.
@@ -97,6 +129,15 @@ class EnginePlugin implements Plugin {
     registerExtension(taskId, ParseHtmlTask.DESCRIPTOR);
   }
 
+  void _registerWorkManagerFactoryExtensions(
+      RegisterExtension registerExtension) {
+    String taskId = WORK_MANAGER_EXTENSION_POINT_ID;
+    registerExtension(taskId,
+        (InternalAnalysisContext context) => new DartWorkManager(context));
+    registerExtension(taskId,
+        (InternalAnalysisContext context) => new HtmlWorkManager(context));
+  }
+
   /**
    * Validate the given extension by throwing an [ExtensionError] if it is not a
    * valid domain.
@@ -107,4 +148,16 @@ class EnginePlugin implements Plugin {
       throw new ExtensionError('Extensions to $id must be a TaskDescriptor');
     }
   }
+
+  /**
+   * Validate the given extension by throwing an [ExtensionError] if it is not a
+   * valid domain.
+   */
+  void _validateWorkManagerFactoryExtension(Object extension) {
+    if (extension is! WorkManagerFactory) {
+      String id = taskExtensionPoint.uniqueIdentifier;
+      throw new ExtensionError(
+          'Extensions to $id must be a WorkManagerFactory');
+    }
+  }
 }

pkg/analyzer/lib/src/task/dart_work_manager.dart

@@ -21,8 +21,8 @@ import 'package:analyzer/src/generated/utilities_collection.dart';
 import 'package:analyzer/src/task/dart.dart';
 import 'package:analyzer/src/task/driver.dart';
 import 'package:analyzer/task/dart.dart';
-import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
+import 'package:analyzer/src/task/html.dart';
 
 /**
  * The manager for Dart specific analysis.
@@ -113,9 +113,7 @@ class DartWorkManager implements WorkManager {
     priorityResultQueue.add(new TargetedResult(target, result));
   }
 
-  /**
-   * Notifies the manager about changes in the explicit source list.
-   */
+  @override
   void applyChange(List<Source> addedSources, List<Source> changedSources,
       List<Source> removedSources) {
     addedSources = addedSources.where(_isDartSource).toList();
@@ -166,18 +164,16 @@ class DartWorkManager implements WorkManager {
     }
   }
 
-  /**
-   * Return an [AnalysisErrorInfo] containing the list of all of the errors and
-   * the line info associated with the given [source]. The list of errors will
-   * be empty if the source is not known to the context or if there are no
-   * errors in the source. The errors contained in the list can be incomplete.
-   */
-  AnalysisErrorInfo getErrors(Source source) {
-    if (analysisCache.getState(source, DART_ERRORS) == CacheState.VALID) {
-      List<AnalysisError> errors = analysisCache.getValue(source, DART_ERRORS);
-      LineInfo lineInfo = analysisCache.getValue(source, LINE_INFO);
-      return new AnalysisErrorInfoImpl(errors, lineInfo);
+  @override
+  List<AnalysisError> getErrors(Source source) {
+    if (!_isDartSource(source) && source is! DartScript) {
+      return AnalysisError.NO_ERRORS;
     }
+    // If analysis is finished, use all the errors.
+    if (analysisCache.getState(source, DART_ERRORS) == CacheState.VALID) {
+      return analysisCache.getValue(source, DART_ERRORS);
+    }
+    // If analysis is in progress, combine all known partial results.
     List<AnalysisError> errors = <AnalysisError>[];
     for (ResultDescriptor descriptor in _SOURCE_ERRORS) {
       errors.addAll(analysisCache.getValue(source, descriptor));
@@ -188,8 +184,7 @@ class DartWorkManager implements WorkManager {
         errors.addAll(analysisCache.getValue(unit, descriptor));
       }
     }
-    LineInfo lineInfo = analysisCache.getValue(source, LINE_INFO);
-    return new AnalysisErrorInfoImpl(errors, lineInfo);
+    return errors;
   }
 
   /**
@@ -315,7 +310,7 @@ class DartWorkManager implements WorkManager {
         }
       });
       if (shouldSetErrors) {
-        AnalysisErrorInfo info = getErrors(target);
+        AnalysisErrorInfo info = context.getErrors(target);
         context.getNotice(target).setErrors(info.errors, info.lineInfo);
       }
     }
@@ -329,7 +324,7 @@ class DartWorkManager implements WorkManager {
         }
       });
       if (shouldSetErrors) {
-        AnalysisErrorInfo info = getErrors(source);
+        AnalysisErrorInfo info = context.getErrors(source);
         context.getNotice(source).setErrors(info.errors, info.lineInfo);
       }
     }

pkg/analyzer/lib/src/task/driver.dart

@@ -9,7 +9,7 @@ import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/engine.dart'
-    hide AnalysisTask, AnalysisContextImpl;
+    hide AnalysisTask, AnalysisContextImpl, WorkManager;
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 import 'package:analyzer/src/generated/utilities_general.dart';
@@ -44,7 +44,8 @@ class AnalysisDriver {
   /**
    * The map of [ComputedResult] controllers.
    */
-  final Map<ResultDescriptor, StreamController<ComputedResult>> resultComputedControllers =
+  final Map<ResultDescriptor,
+          StreamController<ComputedResult>> resultComputedControllers =
       <ResultDescriptor, StreamController<ComputedResult>>{};
 
   /**
@@ -197,8 +198,10 @@ class AnalysisDriver {
    * [descriptor] is computed.
    */
   Stream<ComputedResult> onResultComputed(ResultDescriptor descriptor) {
-    return resultComputedControllers.putIfAbsent(descriptor, () =>
-        new StreamController<ComputedResult>.broadcast(sync: true)).stream;
+    return resultComputedControllers
+        .putIfAbsent(descriptor,
+            () => new StreamController<ComputedResult>.broadcast(sync: true))
+        .stream;
   }
 
   /**
@@ -476,8 +479,9 @@ class InfiniteTaskLoopException extends AnalysisException {
    * Initialize a newly created exception to represent a failed attempt to
    * perform the given [task] due to the given [dependencyCycle].
    */
-  InfiniteTaskLoopException(AnalysisTask task, this.dependencyCycle) : super(
-          'Infinite loop while performing task ${task.descriptor.name} for ${task.target}');
+  InfiniteTaskLoopException(AnalysisTask task, this.dependencyCycle)
+      : super(
+            'Infinite loop while performing task ${task.descriptor.name} for ${task.target}');
 }
 
 /**
@@ -565,10 +569,10 @@ class WorkItem {
    * described by the given descriptor.
    */
   WorkItem(this.context, this.target, this.descriptor, this.spawningResult) {
-    AnalysisTarget actualTarget = identical(
-            target, AnalysisContextTarget.request)
-        ? new AnalysisContextTarget(context)
-        : target;
+    AnalysisTarget actualTarget =
+        identical(target, AnalysisContextTarget.request)
+            ? new AnalysisContextTarget(context)
+            : target;
     Map<String, TaskInput> inputDescriptors =
         descriptor.createTaskInputs(actualTarget);
     builder = new TopLevelTaskInputBuilder(inputDescriptors);
@@ -671,42 +675,6 @@ class WorkItem {
   String toString() => 'Run $descriptor on $target';
 }
 
-/**
- * [AnalysisDriver] uses [WorkManager]s to select results to compute.
- *
- * They know specific of the targets and results they care about,
- * so they can request analysis results in optimal order.
- */
-abstract class WorkManager {
-  /**
-   * Notifies the managers that the given set of priority [targets] was set.
-   */
-  void applyPriorityTargets(List<AnalysisTarget> targets);
-
-  /**
-   * Return the next [TargetedResult] that this work manager wants to be
-   * computed, or `null` if this manager doesn't need any new results.
-   */
-  TargetedResult getNextResult();
-
-  /**
-   * Return the priority if the next work order this work manager want to be
-   * computed. The [AnalysisDriver] will perform the work order with
-   * the highest priority.
-   *
-   * Even if the returned value is [WorkOrderPriority.NONE], it still does not
-   * guarantee that [getNextResult] will return not `null`.
-   */
-  WorkOrderPriority getNextResultPriority();
-
-  /**
-   * Notifies the manager that the given [outputs] were produced for
-   * the given [target].
-   */
-  void resultsComputed(
-      AnalysisTarget target, Map<ResultDescriptor, dynamic> outputs);
-}
-
 /**
  * A description of the work to be done to compute a desired analysis result.
  * The class implements a lazy depth-first traversal of the work item's input.
@@ -773,31 +741,6 @@ class WorkOrder implements Iterator<WorkItem> {
   }
 }
 
-/**
- * The priorities of work orders returned by [WorkManager]s.
- */
-enum WorkOrderPriority {
-  /**
-   * Responding to an user's action.
-   */
-  INTERACTIVE,
-
-  /**
-   * Computing information for priority sources.
-   */
-  PRIORITY,
-
-  /**
-   * A work should be done, but without any special urgency.
-   */
-  NORMAL,
-
-  /**
-   * Nothing to do.
-   */
-  NONE
-}
-
 /**
  * Specilaization of [CycleAwareDependencyWalker] for use by [WorkOrder].
  */

pkg/analyzer/lib/src/task/html_work_manager.dart

@@ -20,7 +20,6 @@ import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/utilities_collection.dart';
 import 'package:analyzer/src/task/driver.dart';
 import 'package:analyzer/src/task/html.dart';
-import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/html.dart';
 import 'package:analyzer/task/model.dart';
 
@@ -71,9 +70,7 @@ class HtmlWorkManager implements WorkManager {
     priorityResultQueue.add(new TargetedResult(target, result));
   }
 
-  /**
-   * Notifies the manager about changes in the explicit source list.
-   */
+  @override
   void applyChange(List<Source> addedSources, List<Source> changedSources,
       List<Source> removedSources) {
     addedSources = addedSources.where(_isHtmlSource).toList();
@@ -103,26 +100,23 @@ class HtmlWorkManager implements WorkManager {
     }
   }
 
-  /**
-   * Return an [AnalysisErrorInfo] containing the list of all of the errors and
-   * the line info associated with the given [source]. The list of errors will
-   * be empty if the source is not known to the context or if there are no
-   * errors in the source. The errors contained in the list can be incomplete.
-   */
-  AnalysisErrorInfo getErrors(Source source) {
-    if (analysisCache.getState(source, HTML_ERRORS) == CacheState.VALID) {
-      List<AnalysisError> errors = analysisCache.getValue(source, HTML_ERRORS);
-      LineInfo lineInfo = analysisCache.getValue(source, LINE_INFO);
-      return new AnalysisErrorInfoImpl(errors, lineInfo);
+  @override
+  List<AnalysisError> getErrors(Source source) {
+    if (!_isHtmlSource(source)) {
+      return AnalysisError.NO_ERRORS;
     }
+    // If analysis is finished, use all the errors.
+    if (analysisCache.getState(source, HTML_ERRORS) == CacheState.VALID) {
+      return analysisCache.getValue(source, HTML_ERRORS);
+    }
+    // If analysis is in progress, combine all known partial results.
     List<AnalysisError> errors = <AnalysisError>[];
     errors.addAll(analysisCache.getValue(source, HTML_DOCUMENT_ERRORS));
     List<DartScript> scripts = analysisCache.getValue(source, DART_SCRIPTS);
     for (DartScript script in scripts) {
       errors.addAll(context.getErrors(script).errors);
     }
-    LineInfo lineInfo = analysisCache.getValue(source, LINE_INFO);
-    return new AnalysisErrorInfoImpl(errors, lineInfo);
+    return errors;
   }
 
   @override
@@ -210,7 +204,7 @@ class HtmlWorkManager implements WorkManager {
         }
       });
       if (shouldSetErrors) {
-        AnalysisErrorInfo info = getErrors(target);
+        AnalysisErrorInfo info = context.getErrors(target);
         context.getNotice(target).setErrors(info.errors, info.lineInfo);
       }
     }

pkg/analyzer/lib/task/model.dart

@@ -7,8 +7,10 @@ library analyzer.task.model;
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart' hide AnalysisTask;
+import 'package:analyzer/src/generated/error.dart' show AnalysisError;
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/source.dart';
+import 'package:analyzer/src/generated/utilities_general.dart';
 import 'package:analyzer/src/task/driver.dart';
 import 'package:analyzer/src/task/model.dart';
 
@@ -389,6 +391,48 @@ abstract class ResultDescriptor<V> {
   TaskInput<V> of(AnalysisTarget target);
 }
 
+/**
+ * A specification of the given [result] for the given [target].
+ *
+ * Clients are not expected to subtype this class.
+ */
+class TargetedResult {
+  /**
+   * An empty list of results.
+   */
+  static final List<TargetedResult> EMPTY_LIST = const <TargetedResult>[];
+
+  /**
+   * The target with which the result is associated.
+   */
+  final AnalysisTarget target;
+
+  /**
+   * The result associated with the target.
+   */
+  final ResultDescriptor result;
+
+  /**
+   * Initialize a new targeted result.
+   */
+  TargetedResult(this.target, this.result);
+
+  @override
+  int get hashCode {
+    return JenkinsSmiHash.combine(target.hashCode, result.hashCode);
+  }
+
+  @override
+  bool operator ==(other) {
+    return other is TargetedResult &&
+        other.target == target &&
+        other.result == result;
+  }
+
+  @override
+  String toString() => '$result for $target';
+}
+
 /**
  * A description of an [AnalysisTask].
  */
@@ -514,3 +558,90 @@ abstract class TaskInputBuilder<V> {
    */
   bool moveNext();
 }
+
+/**
+ * [WorkManager]s are used to drive analysis.
+ *
+ * They know specific of the targets and results they care about,
+ * so they can request analysis results in optimal order.
+ */
+abstract class WorkManager {
+  /**
+   * Notifies the manager about changes in the explicit source list.
+   */
+  void applyChange(List<Source> addedSources, List<Source> changedSources,
+      List<Source> removedSources);
+
+  /**
+   * Notifies the managers that the given set of priority [targets] was set.
+   */
+  void applyPriorityTargets(List<AnalysisTarget> targets);
+
+  /**
+   * Return a list of all of the errors associated with the given [source].
+   * The list of errors will be empty if the source is not known to the context
+   * or if there are no errors in the source. The errors contained in the list
+   * can be incomplete.
+   */
+  List<AnalysisError> getErrors(Source source);
+
+  /**
+   * Return the next [TargetedResult] that this work manager wants to be
+   * computed, or `null` if this manager doesn't need any new results.
+   */
+  TargetedResult getNextResult();
+
+  /**
+   * Return the priority if the next work order this work manager want to be
+   * computed. The [AnalysisDriver] will perform the work order with
+   * the highest priority.
+   *
+   * Even if the returned value is [WorkOrderPriority.NONE], it still does not
+   * guarantee that [getNextResult] will return not `null`.
+   */
+  WorkOrderPriority getNextResultPriority();
+
+  /**
+   * Notifies the manager about analysis options changes.
+   */
+  void onAnalysisOptionsChanged();
+
+  /**
+   * Notifies the manager about [SourceFactory] changes.
+   */
+  void onSourceFactoryChanged();
+
+  /**
+   * Notifies the manager that the given [outputs] were produced for
+   * the given [target].
+   */
+  void resultsComputed(
+      AnalysisTarget target, Map<ResultDescriptor, dynamic> outputs);
+}
+
+/**
+ * The priorities of work orders returned by [WorkManager]s.
+ *
+ * New priorities may be added with time, clients need to tolerate this.
+ */
+enum WorkOrderPriority {
+  /**
+   * Responding to an user's action.
+   */
+  INTERACTIVE,
+
+  /**
+   * Computing information for priority sources.
+   */
+  PRIORITY,
+
+  /**
+   * A work should be done, but without any special urgency.
+   */
+  NORMAL,
+
+  /**
+   * Nothing to do.
+   */
+  NONE
+}

pkg/analyzer/test/generated/engine_test.dart

@@ -31,7 +31,7 @@ import 'package:analyzer/src/generated/testing/element_factory.dart';
 import 'package:analyzer/src/generated/utilities_collection.dart';
 import 'package:analyzer/src/services/lint.dart';
 import 'package:analyzer/src/string_source.dart';
-import 'package:analyzer/task/model.dart' hide AnalysisTask;
+import 'package:analyzer/task/model.dart' hide AnalysisTask, WorkManager;
 import 'package:html/dom.dart' show Document;
 import 'package:path/path.dart' as pathos;
 import 'package:typed_mock/typed_mock.dart';

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

@@ -9,6 +9,7 @@ import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart'
     show
         AnalysisErrorInfo,
+        AnalysisErrorInfoImpl,
         CacheState,
         ChangeNoticeImpl,
         InternalAnalysisContext;
@@ -294,15 +295,12 @@ class DartWorkManagerTest {
     AnalysisError error2 =
         new AnalysisError(source1, 2, 0, ScannerErrorCode.MISSING_DIGIT);
     when(context.getLibrariesContaining(source1)).thenReturn([source2]);
-    LineInfo lineInfo = new LineInfo([0]);
-    entry1.setValue(LINE_INFO, lineInfo, []);
     entry1.setValue(SCAN_ERRORS, <AnalysisError>[error1], []);
     context
         .getCacheEntry(new LibrarySpecificUnit(source2, source1))
         .setValue(VERIFY_ERRORS, <AnalysisError>[error2], []);
-    AnalysisErrorInfo errorInfo = manager.getErrors(source1);
-    expect(errorInfo.errors, unorderedEquals([error1, error2]));
-    expect(errorInfo.lineInfo, lineInfo);
+    List<AnalysisError> errors = manager.getErrors(source1);
+    expect(errors, unorderedEquals([error1, error2]));
   }
 
   void test_getErrors_hasFullList() {
@@ -311,12 +309,9 @@ class DartWorkManagerTest {
     AnalysisError error2 =
         new AnalysisError(source1, 2, 0, ScannerErrorCode.MISSING_DIGIT);
     when(context.getLibrariesContaining(source1)).thenReturn([source2]);
-    LineInfo lineInfo = new LineInfo([0]);
-    entry1.setValue(LINE_INFO, lineInfo, []);
     entry1.setValue(DART_ERRORS, <AnalysisError>[error1, error2], []);
-    AnalysisErrorInfo errorInfo = manager.getErrors(source1);
-    expect(errorInfo.errors, unorderedEquals([error1, error2]));
-    expect(errorInfo.lineInfo, lineInfo);
+    List<AnalysisError> errors = manager.getErrors(source1);
+    expect(errors, unorderedEquals([error1, error2]));
   }
 
   void test_getLibrariesContainingPart() {
@@ -530,12 +525,14 @@ class DartWorkManagerTest {
   }
 
   void test_resultsComputed_errors_forLibrarySpecificUnit() {
+    LineInfo lineInfo = new LineInfo([0]);
     AnalysisError error1 =
         new AnalysisError(source1, 1, 0, ScannerErrorCode.MISSING_DIGIT);
     AnalysisError error2 =
         new AnalysisError(source1, 2, 0, ScannerErrorCode.MISSING_DIGIT);
     when(context.getLibrariesContaining(source1)).thenReturn([source2]);
-    LineInfo lineInfo = new LineInfo([0]);
+    when(context.getErrors(source1))
+        .thenReturn(new AnalysisErrorInfoImpl([error1, error2], lineInfo));
     entry1.setValue(LINE_INFO, lineInfo, []);
     entry1.setValue(SCAN_ERRORS, <AnalysisError>[error1], []);
     AnalysisTarget unitTarget = new LibrarySpecificUnit(source2, source1);
@@ -552,12 +549,14 @@ class DartWorkManagerTest {
   }
 
   void test_resultsComputed_errors_forSource() {
+    LineInfo lineInfo = new LineInfo([0]);
     AnalysisError error1 =
         new AnalysisError(source1, 1, 0, ScannerErrorCode.MISSING_DIGIT);
     AnalysisError error2 =
         new AnalysisError(source1, 2, 0, ScannerErrorCode.MISSING_DIGIT);
     when(context.getLibrariesContaining(source1)).thenReturn([source2]);
-    LineInfo lineInfo = new LineInfo([0]);
+    when(context.getErrors(source1))
+        .thenReturn(new AnalysisErrorInfoImpl([error1, error2], lineInfo));
     entry1.setValue(LINE_INFO, lineInfo, []);
     entry1.setValue(SCAN_ERRORS, <AnalysisError>[error1], []);
     entry1.setValue(PARSE_ERRORS, <AnalysisError>[error2], []);
@@ -615,8 +614,10 @@ class DartWorkManagerTest {
   }
 
   void test_resultsComputed_parsedUnit() {
-    when(context.getLibrariesContaining(source1)).thenReturn([]);
     LineInfo lineInfo = new LineInfo([0]);
+    when(context.getLibrariesContaining(source1)).thenReturn([]);
+    when(context.getErrors(source1))
+        .thenReturn(new AnalysisErrorInfoImpl([], lineInfo));
     entry1.setValue(LINE_INFO, lineInfo, []);
     CompilationUnit unit = AstFactory.compilationUnit();
     manager.resultsComputed(source1, {PARSED_UNIT: unit});
@@ -627,8 +628,10 @@ class DartWorkManagerTest {
   }
 
   void test_resultsComputed_resolvedUnit() {
-    when(context.getLibrariesContaining(source2)).thenReturn([]);
     LineInfo lineInfo = new LineInfo([0]);
+    when(context.getLibrariesContaining(source2)).thenReturn([]);
+    when(context.getErrors(source2))
+        .thenReturn(new AnalysisErrorInfoImpl([], lineInfo));
     entry2.setValue(LINE_INFO, lineInfo, []);
     CompilationUnit unit = AstFactory.compilationUnit();
     manager.resultsComputed(

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

@@ -134,18 +134,15 @@ class HtmlWorkManagerTest {
         new AnalysisError(source1, 1, 0, HtmlErrorCode.PARSE_ERROR, ['']);
     AnalysisError error2 =
         new AnalysisError(source1, 2, 0, HtmlErrorCode.PARSE_ERROR, ['']);
-    LineInfo lineInfo = new LineInfo([0]);
     entry1.setValue(HTML_DOCUMENT_ERRORS, <AnalysisError>[error1], []);
-    entry1.setValue(LINE_INFO, lineInfo, []);
 
     DartScript script = new DartScript(source1, []);
     entry1.setValue(DART_SCRIPTS, [script], []);
     CacheEntry scriptEntry = context.getCacheEntry(script);
     scriptEntry.setValue(DART_ERRORS, [error2], []);
 
-    AnalysisErrorInfo errorInfo = manager.getErrors(source1);
-    expect(errorInfo.errors, unorderedEquals([error1, error2]));
-    expect(errorInfo.lineInfo, lineInfo);
+    List<AnalysisError> errors = manager.getErrors(source1);
+    expect(errors, unorderedEquals([error1, error2]));
   }
 
   void test_getErrors_partialList() {
@@ -153,13 +150,10 @@ class HtmlWorkManagerTest {
         new AnalysisError(source1, 1, 0, HtmlErrorCode.PARSE_ERROR, ['']);
     AnalysisError error2 =
         new AnalysisError(source1, 2, 0, HtmlErrorCode.PARSE_ERROR, ['']);
-    LineInfo lineInfo = new LineInfo([0]);
     entry1.setValue(HTML_DOCUMENT_ERRORS, <AnalysisError>[error1, error2], []);
-    entry1.setValue(LINE_INFO, lineInfo, []);
 
-    AnalysisErrorInfo errorInfo = manager.getErrors(source1);
-    expect(errorInfo.errors, unorderedEquals([error1, error2]));
-    expect(errorInfo.lineInfo, lineInfo);
+    List<AnalysisError> errors = manager.getErrors(source1);
+    expect(errors, unorderedEquals([error1, error2]));
   }
 
   void test_getNextResult_hasNormal_firstIsError() {