hst337
XY Notice
I know about macros, __before_compile__ and other attributes, compiler tracers and such stuff. The question is exactly about implementing wrapper for Elixir compiler which be compatible with Mix.Task.Compiler, nothing else.
The Question
How do I write the Mix.Task.Compiler which will do some global changes to the AST before calling Elixir’s compiler to generate .beam files.
Current solution
Right now my compiler
- Searches for
.exfiles in the path specified byMix.Project.config()[:elixirc_paths] - Calls
Code.string_to_quoted()on each file - Changes the AST
- Calls
Code.compile_quotedwithFile.write!()to the build_path of the binaries returned bycompile_quoted
Current solution drawbacks
- I think it is possible to compile straight to file (without
File.write!) - I think this kind of compilation does not call compiler tracers
- I think it can have some problems with protocol consolidation
- It needs to read/write elixir’s compiler manifest, which is some kind of a private structure.
- It is difficult to change the AST because modules can have compile-time code in their bodies, which I need to preevaluate, to change the code inside functions.
Where Next?
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josevalim
Not possible. By design. We want to avoid anything that goes and globally changes code, without a trace. You can hand roll, as in your current solution, but it will have pitfalls such as losing incremental compilation.
I would suggest taking a step back and discuss what you want to solve and try to find a way that would be considered idiomatic Elixir.
Sorry if this is not the answer you were looking for.
hst337
That’s sad to hear, but I kinda had a feeling that these limitations are intentional. I’ll think about other solutions then, thanks!