How do you looking at the state of a GNU Guix package building between different phases?

General
1

I have a package that takes a non-trivial amount of time to build.

I want to inspect the state of the directory in which it is built between some phases.

How do I do that without running guix build again and again with some print commands strewn in between phases?

2

Got two solutions from ircs://irc.libera.chat/guix (dariqq and another one which you could probably get from the GNU Guix channel logs with a quick grep):

If your phase fails on its own, use the --keep-failed and inspect the directory.

If a phase fails, you do not even have to do anything, except for adding the --keep-failed flag to guix build.

After running the guix build command, somewhere at the end of the guix build command output, there will be a line similar to the following (I am currently working on package libgit2 version 1.9.0), telling you where is the source directory where the package is built:

note: keeping build directory `/tmp/guix-build-libgit2-1.9.0.drv-0'

If no phase fails, add a failing phase after a phase you want to inspect.

Add a new phase called 'debug after the one you want to inspect.

Say you want to inspect the result of the 'build phase:

(add-after 'build 'debug
    (lambda _
        (throw 'debug-error "dropping out")))

Then run the guix build command as you do normally with the --keep-failed flag which stops the GNU Guix build daemon from deleting the source directory.

Now inspect the source directory as above.

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3

I used to put an unbound symbol inside a phase with the -K argument when I want to interrupt the building process and look into the source code but this is more elegant for sure.

(add-after 'build 'debug
    (lambda _
        (throw 'debug-error "dropping out")))

I will make a new “tempel” template with this code. Thanks for the hint @cow_2001.

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