avoid duplicating the RUSTC_LOG env var name

[RalfJung]

We also have the env var name here:

rust/compiler/rustc_driver_impl/src/lib.rs

Lines 1247 to 1251 in c40919b

	/// This allows tools to enable rust logging without having to magically match rustc's
	/// tracing crate version.
	pub fn init_rustc_env_logger() {
	init_env_logger("RUSTC_LOG");
	}

Redundantly having this name twice doesn't seem great. Looks like rustc_log::init_rustc_env_logger is dead code anyway.

r? @oli-obk

[RalfJung]

Hm, this breaks a doctest

rust/compiler/rustc_log/src/lib.rs

Lines 8 to 24 in 569c2fe

	//! ```toml
	//! [dependencies]
	//! rustc_ast = { path = "../rust/compiler/rustc_ast" }
	//! rustc_log = { path = "../rust/compiler/rustc_log" }
	//! rustc_span = { path = "../rust/compiler/rustc_span" }
	//! ```
	//!
	//! ```
	//! fn main() {
	//! rustc_log::init_rustc_env_logger().unwrap();
	//!
	//! let edition = rustc_span::edition::Edition::Edition2021;
	//! rustc_span::create_session_globals_then(edition, || {
	//! /* ... */
	//! });
	//! }
	//! ```

But real tools call rustc_driver::init_rustc_env_logger() anyway, don't they?

[RalfJung]

Cc @dtolnay who added this doctest about a year ago.

[oli-obk]

yea, we should just change that doctest.

[RalfJung]

yea, we should just change that doctest.

To do what? Not importing rustc_driver is the entire point of that test.

We could also just have a constant in rustc_log with the env var name, and avoid the duplication that way.

[oli-obk]

To do what?

just calling init_env_logger("YOUR_TOOL_LOG"). This is just a test, it doesn't have to use or duplicate RUSTC_LOG

[RalfJung]

All right, done.

(The use of set_var is concerning given the plans to make that function unsafe. IMO we should have a function that you give the value of the env var, i.e. the log filter description. Then we could also remove some set_var from Miri. But that's a separate discussion.)

[oli-obk]

@bors r+ rollup

[bors]

📌 Commit 623ed8e has been approved by oli-obk

It is now in the queue for this repository.