Add support for patching class methods.

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
index 576cb96149b00c6e687877b6bb316b0cf38d9cd7..f2bfeb30cb8643607a550a3506f5dabb95d4e898 100644
--- a/pkg/analyzer/lib/src/dart/sdk/patch.dart
+++ b/pkg/analyzer/lib/src/dart/sdk/patch.dart
@@ -72,14 +72,13 @@ class SdkPatcher {
 
       _patchDirectives(
           source, unit, patchSource, patchUnit, addNewTopLevelDeclarations);
-      _patchTopLevelDeclarations(
-          source, unit, patchSource, patchUnit, addNewTopLevelDeclarations);
+      _patchTopLevelDeclarations(unit, patchUnit, addNewTopLevelDeclarations);
     }
   }
 
-  void _failExternalKeyword(Source source, String name, int offset) {
+  void _failExternalKeyword(String name, int offset) {
     throw new ArgumentError(
-        'The keyword "external" was expected for "$name" in $source @ $offset.');
+        'The keyword "external" was expected for "$name" in $_baseDesc @ $offset.');
   }
 
   void _failIfPublicName(AstNode node, String name) {
@@ -99,6 +98,53 @@ class SdkPatcher {
     return 'the line ${location.lineNumber}';
   }
 
+  void _patchClassMembers(
+      ClassDeclaration baseClass, ClassDeclaration patchClass) {
+    List<ClassMember> membersToAppend = [];
+    for (ClassMember patchMember in patchClass.members) {
+      if (patchMember is MethodDeclaration) {
+        String name = patchMember.name.name;
+        if (_hasPatchAnnotation(patchMember.metadata)) {
+          for (ClassMember baseMember in baseClass.members) {
+            if (baseMember is MethodDeclaration &&
+                baseMember.name.name == name) {
+              // Remove the "external" keyword.

[Paul Berry, 2016/10/13 19:09:52]

It looks like we have some duplication between this code and the code in
_patchTopLevelDeclarations (everything between here and "baseMember.body =
newBody").  How about extracting a method to share code?

[scheglov, 2016/10/13 20:18:14]

It does not seem practical to me.
Both "externalKeyword" getter and setter are defined in leaf classes
FunctionDeclaration and MethodDeclaration. And there is not much code to share.
Well, we could use callback, but...

+              Token externalKeyword = baseMember.externalKeyword;
+              if (externalKeyword != null) {
+                baseMember.externalKeyword = null;
+                _removeToken(externalKeyword);
+              } else {
+                _failExternalKeyword(name, baseMember.offset);
+              }
+              // Replace the body.
+              FunctionBody oldBody = baseMember.body;
+              FunctionBody newBody = patchMember.body;
+              _replaceNodeTokens(oldBody, newBody);
+              baseMember.body = newBody;
+            }
+          }
+        } else {
+          _failIfPublicName(patchMember, name);
+          membersToAppend.add(patchMember);
+        }
+      } else {
+        // TODO(scheglov) support field
+        // TODO(scheglov) support constructors
+        String className = patchClass.name.name;
+        _failInPatch('contains an unsupported class member in $className',
+            patchMember.offset);
+      }
+    }
+    // Append new top-level declarations.
+    Token lastToken = baseClass.endToken.previous;
+    for (ClassMember newMember in membersToAppend) {
+      newMember.endToken.setNext(lastToken.next);

[Paul Berry, 2016/10/13 19:09:52]

Consider extracting a method for this logic too.

[scheglov, 2016/10/13 20:18:14]

OK
https://codereview.chromium.org/2417053002

+      lastToken.setNext(newMember.beginToken);
+      baseClass.members.add(newMember);
+      lastToken = newMember.endToken;
+    }
+  }
+
   void _patchDirectives(
       Source baseSource,
       CompilationUnit baseUnit,
@@ -115,12 +161,8 @@ class SdkPatcher {
     }
   }
 
-  void _patchTopLevelDeclarations(
-      Source baseSource,
-      CompilationUnit baseUnit,
-      Source patchSource,
-      CompilationUnit patchUnit,
-      bool addNewTopLevelDeclarations) {
+  void _patchTopLevelDeclarations(CompilationUnit baseUnit,
+      CompilationUnit patchUnit, bool addNewTopLevelDeclarations) {
     List<CompilationUnitMember> declarationsToAppend = [];
     for (CompilationUnitMember patchDeclaration in patchUnit.declarations) {
       if (patchDeclaration is FunctionDeclaration) {
@@ -130,22 +172,19 @@ class SdkPatcher {
             if (patchDeclaration is FunctionDeclaration &&
                 baseDeclaration is FunctionDeclaration &&
                 baseDeclaration.name.name == name) {
-              if (_hasPatchAnnotation(patchDeclaration.metadata)) {
-                // Remove the "external" keyword.
-                Token externalKeyword = baseDeclaration.externalKeyword;
-                if (externalKeyword != null) {
-                  baseDeclaration.externalKeyword = null;
-                  _removeToken(externalKeyword);
-                } else {
-                  _failExternalKeyword(
-                      baseSource, name, baseDeclaration.offset);
-                }
-                // Replace the body.
-                FunctionExpression oldExpr = baseDeclaration.functionExpression;
-                FunctionBody newBody = patchDeclaration.functionExpression.body;
-                _replaceNodeTokens(oldExpr.body, newBody);
-                oldExpr.body = newBody;
+              // Remove the "external" keyword.
+              Token externalKeyword = baseDeclaration.externalKeyword;
+              if (externalKeyword != null) {
+                baseDeclaration.externalKeyword = null;
+                _removeToken(externalKeyword);
+              } else {
+                _failExternalKeyword(name, baseDeclaration.offset);
               }
+              // Replace the body.
+              FunctionExpression oldExpr = baseDeclaration.functionExpression;
+              FunctionBody newBody = patchDeclaration.functionExpression.body;
+              _replaceNodeTokens(oldExpr.body, newBody);
+              oldExpr.body = newBody;
             }
           }
         } else if (addNewTopLevelDeclarations) {
@@ -159,6 +198,19 @@ class SdkPatcher {
         }
         _failIfPublicName(patchDeclaration, patchDeclaration.name.name);
         declarationsToAppend.add(patchDeclaration);
+      } else if (patchDeclaration is ClassDeclaration) {
+        if (_hasPatchAnnotation(patchDeclaration.metadata)) {
+          String name = patchDeclaration.name.name;
+          for (CompilationUnitMember baseDeclaration in baseUnit.declarations) {
+            if (baseDeclaration is ClassDeclaration &&
+                baseDeclaration.name.name == name) {
+              _patchClassMembers(baseDeclaration, patchDeclaration);
+            }
+          }
+        } else {
+          _failIfPublicName(patchDeclaration, patchDeclaration.name.name);
+          declarationsToAppend.add(patchDeclaration);
+        }
       } else {
         _failInPatch('contains an unsupported top-level declaration',
             patchDeclaration.offset);