bug#26170: Bug #26170 Hunting: doc: Explanation of propagated-inputs unclear

[zimoun]

Dear,

The bug 26170 [1] is about the description of “propagated inputs” in the
manual.

Currently, the term “propagated inputs” in the index [2] goes to the
section “Invoking guix package” [3] and explaining:

        Sometimes packages have propagated inputs: these are
        dependencies that automatically get installed along with the
        required package (see propagated-inputs in package objects, for
        information about propagated inputs in package definitions).

        An example is the GNU MPC library: its C header files refer to
        those of the GNU MPFR library, which in turn refer to those of
        the GMP library. Thus, when installing MPC, the MPFR and GMP
        libraries also get installed in the profile; removing MPC also
        removes MPFR and GMP—unless they had also been explicitly
        installed by the user.

with the hyperlink [4] mentioning:

        Lastly, propagated-inputs is similar to inputs, but the
        specified packages will be automatically installed alongside the
        package they belong to (see guix package, for information on how
        guix package deals with propagated inputs).

        For example this is necessary when a C/C++ library needs headers
        of another library to compile, or when a pkg-config file refers
        to another one via its Requires field.

        Another example where propagated-inputs is useful is for
        languages that lack a facility to record the run-time search
        path akin to the RUNPATH of ELF files; this includes Guile,
        Python, Perl, and more. To ensure that libraries written in
        those languages can find library code they depend on at run
        time, run-time dependencies must be listed in propagated-inputs
        rather than inputs.

The initial suggestions of this bug report were:

--8<---------------cut here---------------start------------->8---
1) that `propagated-inputs` are automatically installed *to the Guix
profile* and not just the Store like regular inputs and

2) that C/C++ libraries do not need to be propagated because they can
just as well be loaded from the Store *unless* their header files are
included by header files of another input package (?) and

3) more examples like the above example for GNOME Evolution (which
however I have yet to finish packaging and submit as a patch; maybe
dconf is a better example – I presume it is also needed at run time and
not just).
--8<---------------cut here---------------end--------------->8---

which now appear to me clarified with the current manual.

Does it make sense to close?

All the best,
simon


[1] http://issues.guix.gnu.org/issue/26170 [2]
http://guix.gnu.org/manual/devel/en/guix.html#Concept-Index_cp_letter-P
[3]
http://guix.gnu.org/manual/devel/en/guix.html#index-propagated-inputs
[4] 
http://guix.gnu.org/manual/devel/en/guix.html#package_002dpropagated_002dinputs