Add MapBasedTaskInput.

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

Index: pkg/analyzer/lib/src/task/inputs.dart
diff --git a/pkg/analyzer/lib/src/task/inputs.dart b/pkg/analyzer/lib/src/task/inputs.dart
index bddcfc4441844ba94aa4a950f7d74f29252bffc1..727179958c183c987c39b6d96d713474a76c33c5 100644
--- a/pkg/analyzer/lib/src/task/inputs.dart
+++ b/pkg/analyzer/lib/src/task/inputs.dart
@@ -22,25 +22,17 @@ typedef TaskInput<E> GenerateTaskInputs<E>(Object object);
  * input. Finally, each of the task inputs are used to access analysis results,
  * and the list of the analysis results is used as the input to the task.
  */
-class ListBasedTaskInput<B, E> implements TaskInput<List<E>> {
-  /**
-   * The accessor used to access the list of elements being mapped.
-   */
-  final TaskInput<B> baseAccessor;
-
-  /**
-   * The function used to convert an element in the list returned by the
-   * [baseAccessor] to a task input.
-   */
-  GenerateTaskInputs<E> generateTaskInputs;
-
+class ListBasedTaskInput<B, E>
+    extends _CollectionBasedTaskInput<B, E, List<E>> {
   /**
    * Initialize a result accessor to use the given [baseAccessor] to access a
-   * list of values that can be passed to the given [generateTaskInputs] to generate
-   * a list of task inputs that can be used to access the elements of the input
-   * being accessed.
+   * list of values that can be passed to the given [generateTaskInputs] to
+   * generate a list of task inputs that can be used to access the elements of
+   * the input being accessed.
    */
-  ListBasedTaskInput(this.baseAccessor, this.generateTaskInputs);
+  ListBasedTaskInput(
+      TaskInput<B> baseAccessor, GenerateTaskInputs<E> generateTaskInputs)
+      : super(baseAccessor, generateTaskInputs);
 
   @override
   TaskInputBuilder<List<E>> createBuilder() =>
@@ -50,106 +42,79 @@ class ListBasedTaskInput<B, E> implements TaskInput<List<E>> {
 /**
  * A [TaskInputBuilder] used to build an input based on a [ListBasedTaskInput].
  */
-class ListBasedTaskInputBuilder<B, E> implements TaskInputBuilder<List<E>> {
+class ListBasedTaskInputBuilder<B, E>
+    extends _CollectionBasedTaskInputBuilder<B, E, List<E>> {
   /**
-   * The input being built.
+   * The list of values being built.
    */
-  final ListBasedTaskInput<B, E> input;
+  List<E> _resultValue;
 
   /**
-   * The builder used to build the current result.
+   * Initialize a newly created task input builder that computes the result
+   * specified by the given [input].
    */
-  TaskInputBuilder currentBuilder;
+  ListBasedTaskInputBuilder(ListBasedTaskInput<B, E> input) : super(input);
 
-  /**
-   * The list of values computed by the [input]'s base accessor.
-   */
-  List _baseList = null;
+  @override
+  void _addResultElement(B baseElement, E resultElement) {
+    _resultValue.add(resultElement);
+  }
+
+  @override
+  void _initResultValue() {
+    _resultValue = <E>[];
+  }
+}
 
+/**
+ * An input to an [AnalysisTask] that is computed by the following steps. First
+ * another (base) task input is used to compute a [List]-valued result. An input
+ * generator function is then used to map each element of that list to a task
+ * input. Finally, each of the task inputs are used to access analysis results,
+ * and the map of the base elements to the analysis results is used as the
+ * input to the task.
+ */
+class MapBasedTaskInput<B, E>
+    extends _CollectionBasedTaskInput<B, E, Map<B, E>> {
   /**
-   * The index in the [_baseList] of the value for which a value is currently
-   * being built.
+   * Initialize a result accessor to use the given [baseAccessor] to access a
+   * list of values that can be passed to the given [generateTaskInputs] to
+   * generate a list of task inputs that can be used to access the elements of
+   * the input being accessed.
    */
-  int _baseListIndex = -1;
+  MapBasedTaskInput(
+      TaskInput<B> baseAccessor, GenerateTaskInputs<E> generateTaskInputs)
+      : super(baseAccessor, generateTaskInputs);
 
+  @override
+  TaskInputBuilder<Map<B, E>> createBuilder() =>
+      new MapBasedTaskInputBuilder<B, E>(this);
+}
+
+/**
+ * A [TaskInputBuilder] used to build an input based on a [MapBasedTaskInput].
+ */
+class MapBasedTaskInputBuilder<B, E>
+    extends _CollectionBasedTaskInputBuilder<B, E, Map<B, E>> {
   /**
-   * The list of values being built.
+   * The map being built.
    */
-  List<E> _resultValue = null;
+  Map<B, E> _resultValue;
 
   /**
    * Initialize a newly created task input builder that computes the result
    * specified by the given [input].
    */
-  ListBasedTaskInputBuilder(this.input);
-
-  @override
-  ResultDescriptor get currentResult {
-    if (currentBuilder == null) {
-      return null;
-    }
-    return currentBuilder.currentResult;
-  }
-
-  @override
-  AnalysisTarget get currentTarget {
-    if (currentBuilder == null) {
-      return null;
-    }
-    return currentBuilder.currentTarget;
-  }
+  MapBasedTaskInputBuilder(MapBasedTaskInput<B, E> input) : super(input);
 
   @override
-  void set currentValue(Object value) {
-    if (currentBuilder == null) {
-      throw new StateError(
-          'Cannot set the result value when there is no current result');
-    }
-    currentBuilder.currentValue = value;
+  void _addResultElement(B baseElement, E resultElement) {
+    _resultValue[baseElement] = resultElement;
   }
 
   @override
-  List<E> get inputValue {
-    if (currentBuilder != null || _resultValue == null) {
-      throw new StateError('Result value has not been created');
-    }
-    return _resultValue;
-  }
-
-  @override
-  bool moveNext() {
-    if (currentBuilder == null) {
-      if (_resultValue == null) {
-        // This is the first time moveNext has been invoked, so start by
-        // computing the list of values from which the results will be derived.
-        currentBuilder = input.baseAccessor.createBuilder();
-        return currentBuilder.moveNext();
-      } else {
-        // We have already computed all of the results, so just return false.
-        return false;
-      }
-    }
-    if (currentBuilder.moveNext()) {
-      return true;
-    }
-    if (_resultValue == null) {
-      // We have finished computing the list of values from which the results
-      // will be derived.
-      _baseList = currentBuilder.inputValue;
-      _baseListIndex = 0;
-      _resultValue = <E>[];
-    } else {
-      // We have finished computing one of the elements in the result list.
-      _resultValue.add(currentBuilder.inputValue);
-      _baseListIndex++;
-    }
-    if (_baseListIndex >= _baseList.length) {
-      currentBuilder = null;
-      return false;
-    }
-    currentBuilder =
-        input.generateTaskInputs(_baseList[_baseListIndex]).createBuilder();
-    return currentBuilder.moveNext();
+  void _initResultValue() {
+    _resultValue = new HashMap<B, E>();
   }
 }
 
@@ -377,3 +342,141 @@ class TopLevelTaskInputBuilder
     return currentBuilder.moveNext();
   }
 }
+
+/**
+ * An input to an [AnalysisTask] that is computed by the following steps. First
+ * another (base) task input is used to compute a [List]-valued result. An input

[Brian Wilkerson, 2015/03/12 13:59:47]

The comment needs to be updated.

[scheglov, 2015/03/12 15:10:36]

Actually baseAccessor still provides a List.

But results of *this* input can be any collections.

+ * generator function is then used to map each element of that list to a task
+ * input. Finally, each of the task inputs are used to access analysis results,
+ * and the collection of the analysis results is used as the input to the task.
+ */
+abstract class _CollectionBasedTaskInput<B, E, C> implements TaskInput<C> {

[Brian Wilkerson, 2015/03/12 13:59:47]

Is there a reason to make this class private? (It's ok to make it private
without a good reason, just curious.)

[scheglov, 2015/03/12 15:10:36]

I don't think there is  lot of different data structures that could be useful as
task inputs.
So, if this library provides all of them, there is no reason to open any
intermediate classes.

+  /**
+   * The accessor used to access the list of elements being mapped.
+   */
+  final TaskInput<B> baseAccessor;
+
+  /**
+   * The function used to convert an element in the list returned by the
+   * [baseAccessor] to a task input.
+   */
+  GenerateTaskInputs<E> generateTaskInputs;

[Brian Wilkerson, 2015/03/12 13:59:47]

Should this be final?

[scheglov, 2015/03/12 15:10:36]

Done.

+
+  /**
+   * Initialize a result accessor to use the given [baseAccessor] to access a
+   * list of values that can be passed to the given [generateTaskInputs] to generate
+   * a list of task inputs that can be used to access the elements of the input
+   * being accessed.
+   */
+  _CollectionBasedTaskInput(this.baseAccessor, this.generateTaskInputs);
+}
+
+/**
+ * A [TaskInputBuilder] used to build an input based on a [ListBasedTaskInput].

[Brian Wilkerson, 2015/03/12 13:59:47]

The comment needs to be updated.

[scheglov, 2015/03/12 15:10:36]

Done.

+ */
+abstract class _CollectionBasedTaskInputBuilder<B, E, C>
+    implements TaskInputBuilder<C> {
+  /**
+   * The input being built.
+   */
+  final _CollectionBasedTaskInput<B, E, C> input;
+
+  /**
+   * The builder used to build the current result.
+   */
+  TaskInputBuilder currentBuilder;
+
+  /**
+   * The list of values computed by the [input]'s base accessor.
+   */
+  List _baseList = null;
+
+  /**
+   * The index in the [_baseList] of the value for which a value is currently
+   * being built.
+   */
+  int _baseListIndex = -1;
+
+  /**
+   * Initialize a newly created task input builder that computes the result
+   * specified by the given [input].
+   */
+  _CollectionBasedTaskInputBuilder(this.input);
+
+  @override
+  ResultDescriptor get currentResult {
+    if (currentBuilder == null) {
+      return null;
+    }
+    return currentBuilder.currentResult;
+  }
+
+  @override
+  AnalysisTarget get currentTarget {
+    if (currentBuilder == null) {
+      return null;
+    }
+    return currentBuilder.currentTarget;
+  }
+
+  @override
+  void set currentValue(Object value) {
+    if (currentBuilder == null) {
+      throw new StateError(
+          'Cannot set the result value when there is no current result');
+    }
+    currentBuilder.currentValue = value;
+  }
+
+  @override
+  C get inputValue {
+    if (currentBuilder != null || _resultValue == null) {
+      throw new StateError('Result value has not been created');
+    }
+    return _resultValue;
+  }
+
+  /**
+   * The list of values being built.
+   */
+  C get _resultValue;
+
+  @override
+  bool moveNext() {
+    if (currentBuilder == null) {
+      if (_resultValue == null) {
+        // This is the first time moveNext has been invoked, so start by
+        // computing the list of values from which the results will be derived.
+        currentBuilder = input.baseAccessor.createBuilder();
+        return currentBuilder.moveNext();
+      } else {
+        // We have already computed all of the results, so just return false.
+        return false;
+      }
+    }
+    if (currentBuilder.moveNext()) {
+      return true;
+    }
+    if (_resultValue == null) {
+      // We have finished computing the list of values from which the results
+      // will be derived.
+      _baseList = currentBuilder.inputValue;
+      _baseListIndex = 0;
+      _initResultValue();
+    } else {
+      // We have finished computing one of the elements in the result list.
+      _addResultElement(_baseList[_baseListIndex], currentBuilder.inputValue);
+      _baseListIndex++;
+    }
+    if (_baseListIndex >= _baseList.length) {
+      currentBuilder = null;
+      return false;
+    }
+    currentBuilder =
+        input.generateTaskInputs(_baseList[_baseListIndex]).createBuilder();
+    return currentBuilder.moveNext();
+  }
+
+  void _addResultElement(B baseElement, E resultElement);
+  void _initResultValue();
+}