Re: Turning off tests leads to a different store item

[Maxim Cournoyer]

Hi,

Suhail <suhail@bayesians.ca> writes:

> Felix Lechner via <help-guix@gnu.org> writes:
>
>> On Tue, Oct 31 2023, Julien Lepiller wrote:
>>
>>> You could skip tests, but that would build a different derivation
>>> tree, so it might affect reproducibility
>>
>> Those shortfalls are a consequence of our packaging habits. In an ideal
>> world, would running a test suite ever build a different derivation?

You seem to be confusing 'derivation', which is the build recipe
description that a package "compiles" to, with the package output, the
result of executing the derivation.

While I wouldn't expect the package output to change unless tests are
installed when disabling the test suite, the derivation changes to
account for the different build arguments used (e.g. that #:tests? #t vs
#:tests? #f).

Running tests *may* cause the output derivation to be different.  I
remember a bug in Python that would cause some time stamps to be
embedded in the .pyc when running the test suite (!).  I think it's
safer to assume that a derivation with test enabled is not the same as a
derivation with tests disabled.

There was the "Intensional Store" RFC in Nix that tried to address that
[0]; it may be worth reading but it looks like it comes with a lot of
caveats and complexity.

[0]  https://github.com/NixOS/rfcs/pull/17

-- 
Thanks,
Maxim