Clang Tool: rewrite ObjCMessageExpr

Question

I want to rewrite all messages in my code, I need replace only selectors, but I need be able to replace nested expressions f. e. :

[super foo:[someInstance someMessage:@""] foo2:[someInstance someMessage2]];

I tried do it with clang::Rewriter replaceText and just generate new string, but there is a problem: It would not be work if I change selectors length, because I replace nested messages with those old positions.

So, I assumed that I need to use clang::Rewriter ReplaceStmt(originalStatement, newStatement);

I am using RecursiveASTVisitor to visit all messages, and I want to copy those messages objects, and replace selectors:

How can I do that?

I tried use ObjCMessageExpr::Create but there is so meny args, I don't know how to get ASTContext &Context and ArrayRef<SourceLocation> SeLocs and Expr *Receiver parameters from the original message.

What is the proper way to replace selectors in nested messages using clang tool (clang tooling interface)?

Update:

Should I use ReplaceStmtWithStmt callback and ASTMatchFinder ?

Update:

I am using following function to rewrite text in file:

void ReplaceText(SourceLocation start, unsigned originalLength, StringRef string) { 
    m_rewriter.ReplaceText(start, originalLength, string); 
    m_rewriter.overwriteChangedFiles(); 
} 

And I want to replace all messageExpr in code with new selector f.e: how it was:

[object someMessage:[object2 someMessage:obj3 calculate:obj4]]; 

how it should be:

[object newSelector:[object2 newSelector:obj3 newSelector:obj4]]; 

I am using ReqoursiveASTVisitor:

bool VisitStmt(Stmt *statement) { 
    if (ObjCMessageExpr *messageExpr = dyn_cast<ObjCMessageExpr>(statement)) { 
         ReplaceMessage(*messageExpr) 
    } 
    return true; 
} 

I created method for generating new message expr string:

string StringFromObjCMessageExpr(ObjCMessageExpr& messageExpression) { 
    std::ostringstream stringStream; 
    const string selectorString = messageExpression.getSelector().getAsString(); 
    cout << selectorString << endl; 
    vector<string> methodParts; 
    split(selectorString, ParametersDelimiter, methodParts); 
    stringStream << "[" ; 
    const string receiver = GetStringFromLocations(m_compiler, messageExpression.getReceiverRange().getBegin(), messageExpression.getSelectorStartLoc()); 
    stringStream << receiver; 
    clang::ObjCMessageExpr::arg_iterator argIterator = messageExpression.arg_begin(); 
    for (vector<string>::const_iterator partsIterator = methodParts.begin(); 
         partsIterator != methodParts.end(); 
         ++partsIterator) { 
        stringStream << "newSelector"; 
        if (messageExpression.getNumArgs() != 0) { 
            const clang::Stmt *argument = *argIterator; 
            stringStream << ":" << GetStatementString(*argument) << " "; 
            ++argIterator; 
        } 
    } 
    stringStream << "]"; 
    return stringStream.str(); 
} 

void ReplaceMessage(ObjCMessageExpr& messageExpression) { 
    SourceLocation locStart = messageExpression.getLocStart(); 
    SourceLocation locEnd = messageExpression.getLocEnd(); 
    string newExpr = StringFromObjCMessageExpr(messageExpression); 
    const int exprStringLegth = m_rewriter.getRangeSize(SourceRange(locStart, locEnd)); 
    ReplaceText(locStart, exprStringLegth, newExpr); 
} 

The problem occurs when I try to replace nested messages, like that:

[simpleClass doSomeActionWithString:string3 andAnotherString:string4]; 
[simpleClass doSomeActionWithString:str andAnotherString:str2]; 
[simpleClass doSomeActionWithString:@"" andAnotherString:@"asdasdsad"]; 
[simpleClass setSimpleClassZAZAZAZAZAZAZAZA:[simpleClass getSimpleClassZAZAZAZAZAZAZAZA]];

the result is:

[simpleClass newSelector:string3 newSelector:string4 ]; 
[simpleClass newSelector:str newSelector:str2 ]; 
[simpleClass newSelector:@"" newSelector:@"asdasdsad" ]; 
[simpleClass newSelector:[simpleClass getSimp[simpleClass newSelector]]; 

because messageExpression has "old" value of getLocStart(); and getLocEnd(); How can I fix it?

Answer 1

You can rewrite selector name by replacing only continuous parts of selector name. For example, replace only underlined parts

[object someMessage:[object2 someMessage:obj3 calculate:obj4]];
        ^~~~~~~~~~~          ^~~~~~~~~~~      ^~~~~~~~~

To achieve this you require only

• number of selector parts - ObjCMessageExpr::getNumSelectorLocs()
• their locations - ObjCMessageExpr::getSelectorLoc(index)
• their lengths - ObjCMessageExpr::getSelector().getNameForSlot(index).size().

Overall, you can rewrite ObjCMessageExpr with the following RecursiveASTVisitor:

#include "clang/AST/ASTConsumer.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/Rewrite/Core/Rewriter.h"

namespace clang_tooling
{

using clang::SourceLocation;

class RewritingVisitor : public clang::ASTConsumer,
                         public clang::RecursiveASTVisitor<RewritingVisitor>
{
public:
    // You can obtain SourceManager and LangOptions from CompilerInstance when
    // you are creating visitor (which is also ASTConsumer) in
    // clang::ASTFrontendAction::CreateASTConsumer.
    RewritingVisitor(clang::SourceManager &sourceManager,
                     const clang::LangOptions &langOptions)
        : _sourceManager(sourceManager), _rewriter(sourceManager, langOptions)
    {}

    virtual void HandleTranslationUnit(clang::ASTContext &context)
    {
        TraverseDecl(context.getTranslationUnitDecl());
        _rewriter.overwriteChangedFiles();
    }

    bool VisitObjCMessageExpr(clang::ObjCMessageExpr *messageExpr)
    {
        if (_sourceManager.isInMainFile(messageExpr->getLocStart()))
        {
            clang::Selector selector = messageExpr->getSelector();
            for (unsigned i = 0, end = messageExpr->getNumSelectorLocs();
                 i < end; ++i)
            {
                SourceLocation selectorLoc = messageExpr->getSelectorLoc(i);
                _rewriter.ReplaceText(selectorLoc,
                                      selector.getNameForSlot(i).size(),
                                      "newSelector");
            }
        }
        return Base::VisitObjCMessageExpr(messageExpr);
    }

private:
    typedef clang::RecursiveASTVisitor<RewritingVisitor> Base;

    clang::SourceManager &_sourceManager;
    clang::Rewriter _rewriter;
};

} // end namespace clang_tooling