Add a representation of the information captured from an nnbd migration

Change-Id: Ia201c59ebb31709278ec4efaf7432af757716cf6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/117764
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/src/edit/nnbd_migration/instrumentation_information.dart

@@ -0,0 +1,84 @@
+// Copyright (c) 2019, 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.
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/src/generated/source.dart';
+import 'package:nnbd_migration/instrumentation.dart';
+import 'package:nnbd_migration/nnbd_migration.dart';
+
+/// The instrumentation information gathered from the migration engine.
+class InstrumentationInformation {
+  /// The node used for type sources that are always `null`.
+  NullabilityNodeInfo always;
+
+  /// A map from elements outside of the code being migrated, to the nullability
+  /// nodes associated with the type of the element.
+  final Map<Element, DecoratedTypeInfo> externalDecoratedType = {};
+
+  /// A map from the graph edges between nullability nodes, to information about
+  /// the edge that was created and why it was created.
+  final Map<EdgeInfo, EdgeOriginInfo> edgeOrigin = {};
+
+  /// The node used for type sources that are never `null`.
+  NullabilityNodeInfo never;
+
+  /// A list of the steps in the propagation of nullability information through
+  /// the nullability graph, to report details of the step that was performed
+  /// and why it was performed.
+  final List<PropagationInfo> propagationSteps = [];
+
+  /// The instrumentation information that is specific to a single source.
+  final Map<Source, SourceInformation> sourceInformation = {};
+
+  /// Initialize a newly created holder of instrumentation information.
+  InstrumentationInformation();
+}
+
+/// The instrumentation information gathered from the migration engine that is
+/// specific to a single source.
+class SourceInformation {
+  /// A map from the type annotations found in the source code, to the
+  /// nullability nodes that are associated with that type.
+  final Map<TypeAnnotation, NullabilityNodeInfo> explicitTypeNullability = {};
+
+  /// A map from the fixes that were decided on to the reasons for the fix.
+  final Map<SingleNullabilityFix, List<FixReasonInfo>> fixes = {};
+
+  /// A map from AST nodes that have an implicit return type to the nullability
+  /// node associated with the implicit return type of the AST node. The node
+  /// can be an
+  /// - executable declaration,
+  /// - function-typed formal parameter declaration,
+  /// - function type alias declaration,
+  /// - generic function type, or
+  /// - function expression.
+  final Map<AstNode, DecoratedTypeInfo> implicitReturnType = {};
+
+  /// A map from AST nodes that have an implicit type to the nullability node
+  /// associated with the implicit type of the AST node. The node can be a
+  /// - formal parameter,
+  /// - declared identifier, or
+  /// - variable in a variable declaration list.
+  final Map<AstNode, DecoratedTypeInfo> implicitType = {};
+
+  /// Called whenever the migration engine encounters an AST node with implicit
+  /// type arguments, to report the nullability nodes associated with the
+  /// implicit type arguments of the AST node.
+  ///
+  /// A map from AST nodes that have implicit type arguments to the nullability
+  /// nodes associated with the implicit type arguments of the AST node. The
+  /// node can be a
+  /// - constructor redirection,
+  /// - function expression invocation,
+  /// - method invocation,
+  /// - instance creation expression,
+  /// - list/map/set literal, or
+  /// - type annotation.
+  final Map<AstNode, List<DecoratedTypeInfo>> implicitTypeArguments = {};
+
+  /// Initialize a newly created holder of instrumentation information that is
+  /// specific to a single source.
+  SourceInformation();
+}

pkg/analysis_server/lib/src/edit/nnbd_migration/instrumentation_listener.dart

@@ -0,0 +1,75 @@
+// Copyright (c) 2019, 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.
+
+import 'package:analysis_server/src/edit/nnbd_migration/instrumentation_information.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/src/generated/source.dart';
+import 'package:nnbd_migration/instrumentation.dart';
+import 'package:nnbd_migration/nnbd_migration.dart';
+
+/// A listener used to gather instrumentation information from the migration
+/// engine.
+class InstrumentationListener implements NullabilityMigrationInstrumentation {
+  /// The instrumentation information being gathered.
+  InstrumentationInformation data = InstrumentationInformation();
+
+  /// Initialize a newly created listener.
+  InstrumentationListener();
+
+  @override
+  void explicitTypeNullability(
+      Source source, TypeAnnotation typeAnnotation, NullabilityNodeInfo node) {
+    _sourceInfo(source).explicitTypeNullability[typeAnnotation] = node;
+  }
+
+  @override
+  void externalDecoratedType(Element element, DecoratedTypeInfo decoratedType) {
+    data.externalDecoratedType[element] = decoratedType;
+  }
+
+  @override
+  void fix(SingleNullabilityFix fix, Iterable<FixReasonInfo> reasons) {
+    _sourceInfo(fix.source).fixes[fix] = reasons.toList();
+  }
+
+  @override
+  void graphEdge(EdgeInfo edge, EdgeOriginInfo originInfo) {
+    data.edgeOrigin[edge] = originInfo;
+  }
+
+  @override
+  void immutableNodes(NullabilityNodeInfo never, NullabilityNodeInfo always) {
+    data.never = never;
+    data.always = always;
+  }
+
+  @override
+  void implicitReturnType(
+      Source source, AstNode node, DecoratedTypeInfo decoratedReturnType) {
+    _sourceInfo(source).implicitReturnType[node] = decoratedReturnType;
+  }
+
+  @override
+  void implicitType(
+      Source source, AstNode node, DecoratedTypeInfo decoratedType) {
+    _sourceInfo(source).implicitType[node] = decoratedType;
+  }
+
+  @override
+  void implicitTypeArguments(
+      Source source, AstNode node, Iterable<DecoratedTypeInfo> types) {
+    _sourceInfo(source).implicitTypeArguments[node] = types.toList();
+  }
+
+  @override
+  void propagationStep(PropagationInfo info) {
+    data.propagationSteps.add(info);
+  }
+
+  /// Return the source information associated with the given [source], creating
+  /// it if there has been no previous information for that source.
+  SourceInformation _sourceInfo(Source source) =>
+      data.sourceInformation.putIfAbsent(source, () => SourceInformation());
+}