Update documentation for std::process::Command's new method

[sanchopanca]

In the current documentation, it's not specified that when creating a Command, the .exe extension can be omitted for Windows executables. However, for other types of executable files like .bat or .cmd, the complete filename including the extension must be provided.

I encountered it by noticing that Command::new("wt").spawn().unwrap() succeeds on my machine while Command::new("code").spawn().unwrap() panics. Turns out VS Code's entrypoint is .cmd file.

resolve_exe method mentions this behaviour in a comment, but it makes sense to mention it at a more visible place.

I've added this clarification to the documentation, which should make it more accurate and helpful for Rust developers working on the Windows platform.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @cuviper (or someone else) soon.

Please see the contribution instructions for more information. Namely, in order to ensure the minimum review times lag, PR authors and assigned reviewers should ensure that the review label (S-waiting-on-review and S-waiting-on-author) stays updated, invoking these commands when appropriate:

• @rustbot author: the review is finished, PR author should check the comments and take action accordingly
• @rustbot review: the author is ready for a review, this PR will be queued again in the reviewer's queue

[ChrisDenton]

I would love better documentation here but I'm also a bit reluctant to encourage people to pass .bat files directly to Command::new instead of doing Command::new('cmd.exe').args(&["/c", "script.bat"]) as the former is not well supported (though it should hopefully work in that simple case).

We use CreateProcessW under the hood which says:

To run a batch file, you must start the command interpreter; set lpApplicationName to cmd.exe and set lpCommandLine to the following arguments: /c plus the name of the batch file.

Basically it's only for running .exe files and not script files. But it turned out this wasn't quite true. An undocumented feature is that it did attempt to do this transformation for you when given a .bat file (or .cmd). So when, for security reasons, Rust switched to using its own code to resolve exe paths we attempted to emulate this so as to avoid breaking people's existing code. However, I would still be nervous about people relying on that.

So, yes, I'm in favour of documenting the behaviour but I'm less certain about referencing "other executable files" because as far as CreateProcessW is concerned there's officially only one type of executable file.

[cuviper]

If you don't mind, I'll let you own this review. :)

r? @ChrisDenton

[ChrisDenton]

For sure! As per my comment above I am generally in favour of this but have one concern.

[sanchopanca]

@ChrisDenton thanks for the review. I have incorporated you suggestions.

[ChrisDenton]

Thanks!

@bors r+ rollup

[bors]

📌 Commit 5dea766 has been approved by ChrisDenton

It is now in the queue for this repository.