x.py: chdir to rust root folder, so that x.py can be called from other directories

[RalfJung]

I have my emacs "M-x compile" set up to do ~/path/to/rust/x.py build ..., but emacs will call this from whatever directory the current file is in, which is how I noticed that the working directory does matter for x.py. For example, after changing it, it re-downloads the bootstrap compiler, because that is stored somewhere relative.

Given that cargo also makes it so that the working directory doesn't matter for the build, I felt it'd make sense to implement the same for x.py.

[rust-highfive]

r? @nikomatsakis

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[nikomatsakis]

just as a random hint, M-x recompile will keep the directory and command you started with. But yeah =)

[nikomatsakis]

@bors r+

[bors]

📌 Commit 3bb283f has been approved by nikomatsakis

[RalfJung]

Hm, I just noticed this chdir screws up clicking on filenames in the errors in emacs. So it's not perfect either. I will look at M-x recompile, but I fear "C-c C-c RET" is already too deep in my muscle memory from LaTeX...

[petrochenkov]

@bors r-
Wait, you are breaking out-of-source builds.
Now rustbuild will create everything in the source directory and not where I'm building.

the working directory does matter for x.py

That's exactly the point.

[RalfJung]

Well, but it's annoying for the directory to matter:

$ ./x.py ...
$ cd src
$ ../x.py ... # this will re-download all the bootstraping, and probably recompile other things

[ishitatsuyuki]

I'm against changing cwd. Most of the x.py code is root aware, and invokes the command with an argument to specify target directory.

[nikomatsakis]

D'oh, my bad. This seems like an "obviously ok" change, but I should have solicited broader comment.

[nikomatsakis]

I suggest we just close this, and @RalfJung uses M-x recompile instead. =)

[RalfJung]

I'm against changing cwd. Most of the x.py code is root aware, and invokes the command with an argument to specify target directory.

And that target directory is the pwd? I guess I am not sure what you mean by "root aware".

But, well, I can write a little wrapper script for myself.

[arielb1]

I use x.py several times in different subdirectories with different config.toml settings (debug assertions vs. release vs. cross etc.), and this would break that.

[RalfJung]

I use x.py several times in different subdirectories with different config.toml settings (debug assertions vs. release vs. cross etc.), and this would break that.

I didn't even know that's possible (changing the config.toml depending on the pwd) -- is this documented anywhere?

Anyway, clearly x.py currently deliberately works the way it works, so I'm going to close this PR.