v0.16 new API

[allan2]

This is a breaking fast-forward PR.

std::env::set_var is marked unsafe in the Rust 2024 edition. set_var is used in majority of functions in v0.15.

This PR introduces a non-modifying API for loading of environment variables. Modifying of the environment is also supported with improved ergonomics limiting the use of unsafe.

• introduction of EnvLoader
  • with_path and with_reader entry points with deferred IO
  • supports optional loading and override using EnvSequence
  • non-modifying API with load
  • unsafe modifying API with load_and_modify
  • return type EnvMap is a HashMap newtype with EnvMap::var
• load attribute macro
  • compatible with tokio
  • ergonomic thread-safe loading before the async runtime starts
• Error type contains the variable name
  • VarError is now flattened to Error variants containing the called variable name
• full examples
• from_filename deprecated to prevent directory traversal attack
  • find example added to replicate the old behaviour

More docs and tests have to be added. Feedback is welcome.

Further reading:

• set_var docs
• Add Path to std::env::VarError::NotPresent

Resolves #14, resolves #25, resolves #39, resolves #68, resolves #105, resolves #106, resolves #48 Progresses #112

[aidenfarley]

Would adding a rust-toolchain.toml file with the nightly toolchain specified be beneficial to allow tests to compile?

[allan2]

No, I will revert the edition. More tests and docs still need to be added.

[github-actions[bot]]