Frame for merging scoped lookups (#2661)

* Frame for merging scoped lookups

* rebuild

* Review comments

lib/src/element_type.dart

@@ -16,6 +16,7 @@ import 'package:dartdoc/src/render/element_type_renderer.dart';
 /// may link to a [ModelElement].
 abstract class ElementType extends Privacy with CommentReferable, Nameable {
   final DartType _type;
+  @override
   final PackageGraph packageGraph;
   final ElementType returnedFrom;
   @override

lib/src/generator/templates.runtime_renderers.dart

@@ -2586,6 +2586,19 @@ class _Renderer_CommentReferable extends RendererBase<CommentReferable> {
                         parent: r);
                   },
                 ),
+                'packageGraph': Property(
+                  getValue: (CT_ c) => c.packageGraph,
+                  renderVariable: (CT_ c, Property<CT_> self,
+                          List<String> remainingNames) =>
+                      self.renderSimpleVariable(
+                          c, remainingNames, 'PackageGraph'),
+                  isNullValue: (CT_ c) => c.packageGraph == null,
+                  renderValue:
+                      (CT_ c, RendererBase<CT_> r, List<MustachioNode> ast) {
+                    return renderSimple(c.packageGraph, ast, r.template,
+                        parent: r);
+                  },
+                ),
                 'referenceChildren': Property(
                   getValue: (CT_ c) => c.referenceChildren,
                   renderVariable: (CT_ c, Property<CT_> self,
@@ -2611,6 +2624,17 @@ class _Renderer_CommentReferable extends RendererBase<CommentReferable> {
                         (e) => renderSimple(e, ast, r.template, parent: r));
                   },
                 ),
+                'scope': Property(
+                  getValue: (CT_ c) => c.scope,
+                  renderVariable: (CT_ c, Property<CT_> self,
+                          List<String> remainingNames) =>
+                      self.renderSimpleVariable(c, remainingNames, 'Scope'),
+                  isNullValue: (CT_ c) => c.scope == null,
+                  renderValue:
+                      (CT_ c, RendererBase<CT_> r, List<MustachioNode> ast) {
+                    return renderSimple(c.scope, ast, r.template, parent: r);
+                  },
+                ),
               });
 
   _Renderer_CommentReferable(

lib/src/model/comment_referable.dart

@@ -10,17 +10,37 @@ library dartdoc.src.model.comment_reference;
 import 'dart:core';
 
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/scope.dart';
 import 'package:dartdoc/dartdoc.dart';
 import 'package:meta/meta.dart';
 
 class ReferenceChildrenLookup {
   final String lookup;
   final List<String> remaining;
+
   ReferenceChildrenLookup(this.lookup, this.remaining);
+
+  @override
+  String toString() => '$lookup.${remaining.join(".")}';
+}
+
+extension on Scope {
+  /// Prefer the getter for a bundled lookup if both exist.
+  Element lookupPreferGetter(String id) {
+    var result = lookup(id);
+    return result.getter ?? result.setter;
+  }
 }
 
 /// Support comment reference lookups on a Nameable object.
 mixin CommentReferable implements Nameable {
+  PackageGraph packageGraph;
+
+  /// For any [CommentReferable] where an analyzer [Scope] exists (or can
+  /// be constructed), implement this.  This will take priority over
+  /// lookups via [referenceChildren].  Can be cached.
+  Scope get scope => null;
+
   /// Look up a comment reference by its component parts.  If [tryParents] is
   /// true, try looking up the same reference in any parents of [this].
   /// Will skip over results that do not pass a given [filter] and keep
@@ -37,20 +57,14 @@ mixin CommentReferable implements Nameable {
 
     /// Search for the reference.
     for (var referenceLookup in childLookups(reference)) {
+      if (scope != null) {
+        result = lookupViaScope(referenceLookup, filter);
+        if (result != null) break;
+      }
       if (referenceChildren.containsKey(referenceLookup.lookup)) {
-        result = referenceChildren[referenceLookup.lookup];
-        if (referenceLookup.remaining.isNotEmpty) {
-          result = result?.referenceBy(referenceLookup.remaining,
-              tryParents: false, filter: filter);
-        } else if (!filter(result)) {
-          result = result?.referenceBy([referenceLookup.lookup],
-              tryParents: false, filter: filter);
-        }
-        if (!filter(result)) {
-          result = null;
-        }
+        result = _lookupViaReferenceChildren(referenceLookup, filter);
+        if (result != null) break;
       }
-      if (result != null) break;
     }
     // If we can't find it in children, try searching parents if allowed.
     if (result == null && tryParents) {
@@ -62,6 +76,51 @@ mixin CommentReferable implements Nameable {
     return result;
   }
 
+  /// Looks up references by [scope], skipping over results that do not match
+  /// the given filter.
+  ///
+  /// Override if [Scope.lookup] may return a [PrefixElement] or other elements
+  /// not corresponding to a [CommentReferable], but you still want to have
+  /// an implementation of [scope].
+  CommentReferable lookupViaScope(ReferenceChildrenLookup referenceLookup,
+      bool Function(CommentReferable) filter) {
+    var resultElement = scope.lookupPreferGetter(referenceLookup.lookup);
+    if (resultElement is PrefixElement) {
+      assert(false,
+          'PrefixElement detected, override [lookupViaScope] in subclass');
+      return null;
+    }
+    return recurseChildrenAndFilter(referenceLookup,
+        ModelElement.fromElement(resultElement, packageGraph), filter);
+  }
+
+  CommentReferable _lookupViaReferenceChildren(
+          ReferenceChildrenLookup referenceLookup,
+          bool Function(CommentReferable) filter) =>
+      recurseChildrenAndFilter(
+          referenceLookup, referenceChildren[referenceLookup.lookup], filter);
+
+  /// Given a [result] found in an implementation of [lookupViaScope] or
+  /// [_lookupViaReferenceChildren], recurse through children, skipping over
+  /// results that do not match the filter.
+  CommentReferable recurseChildrenAndFilter(
+      ReferenceChildrenLookup referenceLookup,
+      CommentReferable result,
+      bool Function(CommentReferable) filter) {
+    assert(result != null);
+    if (referenceLookup.remaining.isNotEmpty) {
+      result = result.referenceBy(referenceLookup.remaining,
+          tryParents: false, filter: filter);
+    } else if (!filter(result)) {
+      result = result.referenceBy([referenceLookup.lookup],
+          tryParents: false, filter: filter);
+    }
+    if (!filter(result)) {
+      result = null;
+    }
+    return result;
+  }
+
   /// A list of lookups that should be attempted on children based on
   /// [reference].  This allows us to deal with libraries that may have
   /// separators in them. [referenceBy] stops at the first one found.
@@ -71,8 +130,10 @@ mixin CommentReferable implements Nameable {
       ];
 
   /// Map of name to the elements that are a member of [this], but
-  /// not this model element itself.
-  /// Can be cached.
+  /// not this model element itself.  Can be cached.
+  ///
+  /// There is no need to duplicate references here that can be found via
+  /// [scope].
   Map<String, CommentReferable> get referenceChildren;
 
   /// Iterable of immediate "parents" to try resolving component parts.

lib/src/model/package_graph.dart

@@ -267,6 +267,7 @@ class PackageGraph with CommentReferable, Nameable {
 
   bool get hasFooterVersion => !config.excludeFooterVersion;
 
+  @override
   PackageGraph get packageGraph => this;
 
   /// Map of package name to Package.

test/comment_referable/comment_referable_test.dart

@@ -25,7 +25,7 @@ abstract class Base extends Nameable with CommentReferable {
   Element get element => throw UnimplementedError();
 }
 
-class Top extends Base with CommentReferable {
+class Top extends Base {
   @override
   final String name;
   final List<TopChild> children;