MACRO&COMP: let a proc macro know if it is invoked during completion

[vlad20012]

Now the plugin sets these environment variables when expands a proc macro during completion: RUST_IDE_PROC_MACRO_COMPLETION=1
RUST_IDE_PROC_MACRO_COMPLETION_DUMMY_IDENTIFIER=IntellijIdeaRulezzz

changelog: Experimentally set RUST_IDE_PROC_MACRO_COMPLETION and RUST_IDE_PROC_MACRO_COMPLETION_DUMMY_IDENTIFIER environment variables for procedural macro when invoking them during completion. The idea is that authors of proc macros could use these variables and based on them change behavior of the macro to provide a better (possible custom) completion for IDE users

[Undin]

Are these variables already taken into account by proc macro expander, or do we want to add this support in future?

[vlad20012]

The idea is that authors of proc macros could use these variables (in the future) and based on them change behavior of the macro to provide a better (possible custom) completion for IDE users. I made a PoC version for html! macro from yew and it seems to work. I'm going to open a PR in yew repo and so start a discussion about custom completion in proc macros, but I think we should start with setting these envs on our side

[vlad20012]

bors r+

[bors]

Build succeeded:

• check

[Dr-Emann]

Is it possible to do something like this for build scripts as well? If I have a build script that outputs a huge phf map, I think IDE performance could be improved by only building a much smaller map when built for IDE uses?