Add SdkPatcher and implement top-level function / getter / setter patching.

pkg/analyzer/lib/src/dart/sdk/patch.dart

Index: pkg/analyzer/lib/src/dart/sdk/patch.dart
diff --git a/pkg/analyzer/lib/src/dart/sdk/patch.dart b/pkg/analyzer/lib/src/dart/sdk/patch.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3a5e5acab8a4e8b00e2c462dce9b2ddb66cd935a
--- /dev/null
+++ b/pkg/analyzer/lib/src/dart/sdk/patch.dart
@@ -0,0 +1,149 @@
+// 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.
+
+library analyzer.src.dart.sdk.patch;
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/token.dart';
+import 'package:analyzer/error/listener.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/src/dart/scanner/reader.dart';
+import 'package:analyzer/src/dart/scanner/scanner.dart';
+import 'package:analyzer/src/dart/sdk/sdk.dart';
+import 'package:analyzer/src/generated/parser.dart';
+import 'package:analyzer/src/generated/sdk.dart';
+import 'package:analyzer/src/generated/source.dart';
+import 'package:meta/meta.dart';
+import 'package:path/src/context.dart';
+
+/**
+ * [SdkPatcher] applies patches to SDK [CompilationUnit].
+ */
+class SdkPatcher {
+  /**
+   * Patch the given [unit] of a SDK [source] with the patches defined in
+   * the [sdk] for the given [platform].  Throw [ArgumentError] if a patch
+   * file cannot be read, or the contents violates rules for patch files.
+   *
+   * If [addNewTopLevelDeclarations] is `true`, then the [unit] is the
+   * defining unit of a library, so new top-level declarations should be
+   * added to this unit.  For parts new declarations may be added only to the
+   * patched classes.
+   *
+   * TODO(scheglov) auto-detect [addNewTopLevelDeclarations]
+   */
+  void patch(FolderBasedDartSdk sdk, int platform,
+      AnalysisErrorListener errorListener, Source source, CompilationUnit unit,
+      {bool addNewTopLevelDeclarations: true}) {
+    // Prepare the patch files to apply.
+    List<String> patchPaths;
+    {
+      // TODO(scheglov) add support for patching parts
+      String uriStr = source.uri.toString();
+      SdkLibrary sdkLibrary = sdk.getSdkLibrary(uriStr);
+      if (sdkLibrary == null) {
+        throw new ArgumentError(
+            'The library $uriStr is not defined in the SDK.');
+      }
+      patchPaths = sdkLibrary.getPatches(platform);
+    }
+
+    bool strongMode = sdk.analysisOptions.strongMode;
+    Context pathContext = sdk.resourceProvider.pathContext;
+    for (String path in patchPaths) {
+      String pathInLib = pathContext.joinAll(path.split('/'));
+      File patchFile = sdk.libraryDirectory.getChildAssumingFile(pathInLib);
+      if (!patchFile.exists) {
+        throw new ArgumentError(
+            'The patch file ${patchFile.path} does not exist.');
+      }
+      Source patchSource = patchFile.createSource();
+      CompilationUnit patchUnit = parse(patchSource, strongMode, errorListener);
+      _patchTopLevelDeclarations(
+          source, unit, patchSource, patchUnit, addNewTopLevelDeclarations);
+    }
+  }
+
+  void _failExternalKeyword(Source source, String name, int offset) {
+    throw new ArgumentError(
+        'The keyword "external" was expected for "$name" in $source @ $offset.');
+  }
+
+  void _patchTopLevelDeclarations(
+      Source baseSource,
+      CompilationUnit baseUnit,
+      Source patchSource,
+      CompilationUnit patchUnit,
+      bool addNewTopLevelDeclarations) {
+    List<CompilationUnitMember> declarationsToAppend = [];
+    for (CompilationUnitMember patchDeclaration in patchUnit.declarations) {
+      if (patchDeclaration is FunctionDeclaration) {
+        String name = patchDeclaration.name.name;
+        if (_hasPatchAnnotation(patchDeclaration.metadata)) {
+          for (CompilationUnitMember baseDeclaration in baseUnit.declarations) {
+            if (patchDeclaration is FunctionDeclaration &&
+                baseDeclaration is FunctionDeclaration &&
+                baseDeclaration.name.name == name) {
+              if (_hasPatchAnnotation(patchDeclaration.metadata)) {
+                // Remove the "external" keyword.
+                if (baseDeclaration.externalKeyword != null) {
+                  baseDeclaration.externalKeyword = null;
+                } else {
+                  _failExternalKeyword(
+                      baseSource, name, baseDeclaration.offset);
+                }
+                // Replace the body.
+                baseDeclaration.functionExpression.body =
+                    patchDeclaration.functionExpression.body;
+              }
+            }
+          }
+        } else if (addNewTopLevelDeclarations) {
+          // No @patch, must be private.
+          if (!Identifier.isPrivateName(name)) {
+            throw new ArgumentError(
+                'The patch file $patchSource attempts to append '
+                'a non-private declaration "$name".');
+          }
+          declarationsToAppend.add(patchDeclaration);
+        }
+      }
+    }
+    // Append new top-level declarations.
+    baseUnit.declarations.addAll(declarationsToAppend);
+  }
+
+  /**
+   * Parse the given [source] into AST.
+   */
+  @visibleForTesting
+  static CompilationUnit parse(
+      Source source, bool strong, AnalysisErrorListener errorListener) {
+    String code = source.contents.data;
+
+    CharSequenceReader reader = new CharSequenceReader(code);
+    Scanner scanner = new Scanner(source, reader, errorListener);
+    scanner.scanGenericMethodComments = strong;
+    Token token = scanner.tokenize();
+    LineInfo lineInfo = new LineInfo(scanner.lineStarts);
+
+    Parser parser = new Parser(source, errorListener);
+    parser.parseGenericMethodComments = strong;
+    CompilationUnit unit = parser.parseCompilationUnit(token);
+    unit.lineInfo = lineInfo;
+    return unit;
+  }
+
+  /**
+   * Return `true` if [metadata] has the `@patch` annotation.
+   */
+  static bool _hasPatchAnnotation(List<Annotation> metadata) {
+    return metadata.any((annotation) {
+      Identifier name = annotation.name;
+      return annotation.constructorName == null &&
+          name is SimpleIdentifier &&
+          name.name == 'patch';
+    });
+  }
+}