Document `RUSTUP_WINDOWS_PATH_ADD_BIN`

[BD103]

RUSTUP_WINDOWS_PATH_ADD_BIN, as mentioned in #3703, isn't documented on the website: https://rust-lang.github.io/rustup/environment-variables.html. I think it should be documented, however, because it's useful when writing a program that links to rustc_driver.dll. (See TheBevyFlock/bevy_cli#267 for context.)

[ChrisDenton]

This will be default enabled in the next version of rustup and, once that transition is successful, the intent is to eventually remove the option entirely.

[BD103]

This will be default enabled in the next version of rustup and, once that transition is successful, the intent is to eventually remove the option entirely.

I'm not sure I understand. Are you implying that RUSTUP_WINDOWS_PATH_ADD_BIN=1 will become the default next release, reverting #3507?

[ChrisDenton]

Oh sorry, you're right. I got that true/false flipped around. The default will indeed be false.

[ehuss]

I didn't really intend it to be permanent. I'm not sure if it really makes sense to keep it, since it is quite a hack (and will break things if you change its value). One solution is to query the path like nextest does. I'm not sure if there is really a good solution here.

[BD103]

Oh sorry, you're right. I got that true/false flipped around. The default will indeed be false.

No worries! :)

I didn't really intend it to be permanent. I'm not sure if it really makes sense to keep it, since it is quite a hack (and will break things if you change its value). One solution is to query the path like nextest does. I'm not sure if there is really a good solution here.

I'm using RUSTUP_WINDOWS_PATH_ADD_BIN in a closed environment where I control spawning cargo and rustc, meaning I can ensure that they do not accidentally use the proxy +toolchain syntax. This is nice, as I don't have to worry about breaking anything beyond my control.

Though I realize I'm in the minority here, I still think RUSTUP_WINDOWS_PATH_ADD_BIN is useful enough to keep. I think a compromise can be found here, perhaps by:

• Adding a warning that setting RUSTUP_WINDOWS_PATH_ADD_BIN may break programs that you call, especially user-defined ones.
• Marking the variable as unstable, and that it may be removed at any point. (And suggest modifying the PATH yourself instead.)

As a side note, how does nextest query what folders need to be added to the path? In case you do decide to remove RUSTUP_WINDOWS_PATH_ADD_BIN, I'll need to switch my code to use that instead.

[ehuss]

Sorry, meant to link to #3825, where there is more discussion about this. I don't really know much about nextest, but they linked nextest-rs/nextest#1499.

[BD103]

Thank you! For now I'll continue using RUSTUP_WINDOWS_PATH_ADD_BIN, but I'll keep an eye on #3825 in case it becomes deprecated / removed in the future.

[sunshowers]

As a side note, how does nextest query what folders need to be added to the path?

Painstakingly, by hand -- see:

• https://github.com/nextest-rs/nextest/blob/931b30286e6cc0697062faba661ae457a59695e6/nextest-runner/src/rustc_cli.rs#L31-L38
• https://github.com/nextest-rs/nextest/blob/931b30286e6cc0697062faba661ae457a59695e6/nextest-runner/src/platform.rs#L412-L499