Rename some index fields and use single 'UnitIndex.unit' field.

pkg/analyzer/lib/src/summary/index_unit.dart

 // Copyright (c) 2016, 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/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/idl.dart';
 
 /**
  * Object that gathers information about the whole package index and then uses
  * it to assemble a new [PackageIndexBuilder].  Call [index] on each compilation
  * unit to be indexed, then call [assemble] to retrieve the complete index for
  * the package.
  */
 class PackageIndexAssembler {
   /**
    * Map associating referenced elements with their [_ElementInfo]s.
    */
   final Map<Element, _ElementInfo> _elementMap = <Element, _ElementInfo>{};
 
   /**
    * Map associating [CompilationUnitElement]s with their identifiers, which
-   * are indices into [_elementLibraryUris] and [_elementUnitUris].
+   * are indices into [_unitLibraryUris] and [_unitUnitUris].
    */
-  final Map<CompilationUnitElement, int> _elementUnitMap =
+  final Map<CompilationUnitElement, int> _unitMap =
       <CompilationUnitElement, int>{};
 
   /**
    * Each item of this list corresponds to the library URI of a unique
    * [CompilationUnitElement].  It is an index into [_strings].
    */
-  final List<int> _elementLibraryUris = <int>[];
+  final List<int> _unitLibraryUris = <int>[];
 
   /**
    * Each item of this list corresponds to the unit URI of a unique
    * [CompilationUnitElement].  It is an index into [_strings].
    */
-  final List<int> _elementUnitUris = <int>[];
+  final List<int> _unitUnitUris = <int>[];
 
   /**
    * Map associating strings with their identifiers, which are indices
    * into [_strings].
    */
   final Map<String, int> _stringMap = <String, int>{};
 
   /**
    * List of unique strings used in this index.
    */
@@ skipping 10 matching lines @@
    */
   PackageIndexBuilder assemble() {
     List<_ElementInfo> elementInfoList = _elementMap.values.toList();
     elementInfoList.sort((a, b) {
       return a.offset - b.offset;
     });
     for (int i = 0; i < elementInfoList.length; i++) {
       elementInfoList[i].id = i;
     }
     return new PackageIndexBuilder(
-        elementLibraryUris: _elementLibraryUris,
-        elementUnitUris: _elementUnitUris,
+        unitLibraryUris: _unitLibraryUris,
+        unitUnitUris: _unitUnitUris,
         elementUnits: elementInfoList.map((e) => e.unitId).toList(),
         elementOffsets: elementInfoList.map((e) => e.offset).toList(),
         elementKinds: elementInfoList.map((e) => e.kind).toList(),
         strings: _strings,
         units: _units.map((unit) => unit.assemble()).toList());
   }
 
   /**
    * Index the given fully resolved [unit].
    */
   void index(CompilationUnit unit) {
     CompilationUnitElement unitElement = unit.element;
     _UnitIndexAssembler assembler = new _UnitIndexAssembler(this, unitElement);
     _units.add(assembler);
     unit.accept(new _IndexContributor(assembler));
   }
 
   /**
    * Return the unique [_ElementInfo] corresponding the [element].  The field
    * [_ElementInfo.id] is filled by [assemble] during final sorting.
    */
   _ElementInfo _getElementInfo(Element element) {
     return _elementMap.putIfAbsent(element, () {
       CompilationUnitElement unitElement = getUnitElement(element);
-      int unitId = _getUnitElementId(unitElement);
+      int unitId = _getUnitId(unitElement);
       int offset = element.nameOffset;
       if (element is LibraryElement || element is CompilationUnitElement) {
         offset = 0;
       }
       IndexSyntheticElementKind kind = getIndexElementKind(element);
       return new _ElementInfo(unitId, offset, kind);
     });
   }
 
   /**
    * Add information about [str] to [_strings] if necessary, and return the
    * location in this array representing [str].
    */
   int _getStringId(String str) {
     return _stringMap.putIfAbsent(str, () {
       int id = _strings.length;
       _strings.add(str);
       return id;
     });
   }
 
   /**
-   * Add information about [unitElement] to [_elementUnitUris] and
-   * [_elementLibraryUris] if necessary, and return the location in those
+   * Add information about [unitElement] to [_unitUnitUris] and
+   * [_unitLibraryUris] if necessary, and return the location in those
    * arrays representing [unitElement].
    */
-  int _getUnitElementId(CompilationUnitElement unitElement) {
-    return _elementUnitMap.putIfAbsent(unitElement, () {
-      assert(_elementLibraryUris.length == _elementUnitUris.length);
-      int id = _elementUnitUris.length;
-      _elementLibraryUris.add(_getUriId(unitElement.library.source.uri));
-      _elementUnitUris.add(_getUriId(unitElement.source.uri));
+  int _getUnitId(CompilationUnitElement unitElement) {
+    return _unitMap.putIfAbsent(unitElement, () {
+      assert(_unitLibraryUris.length == _unitUnitUris.length);
+      int id = _unitUnitUris.length;
+      _unitLibraryUris.add(_getUriId(unitElement.library.source.uri));
+      _unitUnitUris.add(_getUriId(unitElement.source.uri));
       return id;
     });
   }
 
   /**
    * Return the identifier corresponding to [uri].
    */
   int _getUriId(Uri uri) {
     String str = uri.toString();
     return _getStringId(str);
@@ skipping 444 matching lines @@
    * by [addRelation] and [defineName].
    */
   UnitIndexBuilder assemble() {
     relations.sort((a, b) {
       return a.elementInfo.id - b.elementInfo.id;
     });
     definedNames.sort((a, b) {
       return a.nameId - b.nameId;
     });
     return new UnitIndexBuilder(
+        unit: pkg._getUnitId(unitElement),

[Paul Berry, 2016/02/29 18:39:01]

I don't think this is a bug but I'm nervous about it. 
PackageIndexAssembler.assemble() stores _unitLibraryUris and _unitUnitUris in
the PackageIndexBuilder prior to calling _UnitIndexAssembler.assemble().  Which
means that we might wind up calling pkg._getUnitId() (which could modify those
lists) after they've been stored in PackageIndexBuilder.

Fortunately, the PackageIndexBuilder constructor doesn't make copies of
_unitLibraryUris and _unitUnitUris, so we are ok.  But that's an implementation
detail of PackageIndexBuilder that we shouldn't rely on--if we ever changed it
so that it *did* make copies, this code would break.

I would prefer to have an implementation that doesn't rely on the fact that
PackageIndexBuilder doesn't make copies.

Possible solution: move the call to pkg._getUnitId() into the
_UnitIndexAssembler constructor, and store its return value as a field in
_UnitIndexAssembler rather than storing [unitElement].

[scheglov, 2016/02/29 18:48:27]

Thank you.
I changed it to pass unitId into the UnitIndex constructor.

         definedNames: definedNames.map((n) => n.nameId).toList(),
         definedNameKinds: definedNames.map((n) => n.kind).toList(),
         definedNameOffsets: definedNames.map((n) => n.offset).toList(),
-        elements: relations.map((r) => r.elementInfo.id).toList(),
-        kinds: relations.map((r) => r.kind).toList(),
-        locationOffsets: relations.map((r) => r.offset).toList(),
-        locationLengths: relations.map((r) => r.length).toList(),
-        libraryUri: pkg._getUriId(unitElement.library.source.uri),
-        unitUri: pkg._getUriId(unitElement.source.uri));
+        usedElements: relations.map((r) => r.elementInfo.id).toList(),
+        usedElementKinds: relations.map((r) => r.kind).toList(),
+        usedElementOffsets: relations.map((r) => r.offset).toList(),
+        usedElementLengths: relations.map((r) => r.length).toList());
   }
 
   void defineName(String name, IndexNameKind kind, int offset) {
     int nameId = pkg._getStringId(name);
     definedNames.add(new _DefinedNameInfo(nameId, kind, offset));
   }
 }