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Feature gate: #![feature(proc_macro_tracked_env, proc_macro_tracked_path)]

This is a tracking issue for proc_macro::tracked*, to allow adding files and environment variables to the build system's dependency tracking.

Public API

// proc_macro

mod tracked {
    pub fn env_var<K: AsRef<OsStr> + AsRef<str>>(key: K) -> > Result<String, VarError>;
    pub fn path<P: AsRef<Path>>(path: P);
}

Steps / History

• Implementation of tracked_env::var: proc_macro: Add API for tracked access to environment variables #74653
• Implementation of tracked_path::path: add track_path::path fn for usage in proc_macros #84029
• Add tracking issue: Use new tracking issue for proc_macro::tracked_*. #99516
• Change path to accept AsRef<Path> instead of AsRef<str>
• Design the public API
• Documentation
• Final comment period (FCP)
• Stabilization PR

Unresolved Questions

• The full API design.
  • The implementaiton PRs were mostly focussed on the implementation details behind the scenes of proc_macro, but there's barely been any discussion on the public interface.