AST of other Files in Tweaks

LLVM Project clangd
#1

Hello,

I am currently developing some new Tweaks (FixIts, Refactoring functions or whatever you wanna call them) in clangd. I am trying to develop a multi-file tweak, but it seems that from Tweak::Selection I can only get the AST of the current main file. Is there a way to get the AST of other files inside of a Tweak::apply() implementation? I found the location of my symbols in other files with locateSymbolAt(), but I need more information about that symbol.

Thanks
Mirko

#2

There is currently no infrastructure in place to get the ASTs for other files in the tweaks. All you can do really query the SymbolIndex and read the source files.

#3

Thanks for the reply!
What would be the best way to extract the SourceRange of a symbol ( in my case function definition and static variable definitions) in these other files?

I could try to write a small parser myself, but I guess that’s not the way to go.

#4

You can find this information in the index. The exact workflow will depend on the scenario, but if e.g. you’re looking for the source range of the definition of a symbol which is referenced in the main AST, you could:

  • Use getSymbolID(const Decl*) to compute a SymbolID for the symbol
  • Use SymbolIndex::lookup() to look up the Symbol correponding to the SymbolID
  • The source range is contained within Symbol::Definition
#5

That would only get the source range of the identifier not the whole function or static variable definition, which I think is what he is after.

#6

I think it is not in the main AST since getDefinition() returns a null-ptr(my main file is a header and the defnition is in the cpp file). Thats why I use the locateSymbolAt() function.

#7

@njames93 yes, that is right.

#8

I just meant referenced in the main AST, such that you can get a Decl* for it.

Indeed, the full range is not stored in the index. We could perhaps consider storing it, it would fix Populate TypeHierarchyItem.range correctly for subtypes · Issue #59 · clangd/clangd · GitHub as well.

#9

Ok, but how would I build here a lightweight AST (dunno if there are different modes) that contains the information I need. I cannot really find anything about this.

#10

I don’t think there is anything like a “lightweight AST” in clang right now. The closest thing I know of is FrontendOpts.SkipFunctionBodies which makes the building of a regular AST somewhat faster, but parsing declarations (particularly in included headers) is still going to take a while.

There’s been talk of a “pseudoparser” which doesn’t look at included headers, but I don’t believe such a thing exists in clang yet.

#11

Ok thanks, then I will write something small myself.