modules/dnf: Substitute variables in DNF cache path (#80094)

The cache directory can be specified with variables that are expanded by DNF, for example,

```
cachedir=/var/cache/yum/$basearch/$releasever
```

But the `dnf` module would use that path literally, instead of replacing
`$basearch` and `$releasever` with their values.

This commit ensures that variables in `cachedir` are properly substituted.

Signed-off-by: Benoît Knecht <bknecht@protonmail.ch>

changelogs/fragments/dnf_cache_path.yml

@@ -0,0 +1,3 @@
+---
+bugfixes:
+  - dnf - Substitute variables in DNF cache path (https://github.com/ansible/ansible/pull/80094).

lib/ansible/modules/dnf.py

@@ -403,6 +403,7 @@ from ansible.module_utils.yumdnf import YumDnf, yumdnf_argument_spec
 # to set proper locale before importing dnf to be able to scrape
 # the output in some cases (FIXME?).
 dnf = None
+libdnf = None
 
 
 class DnfModule(YumDnf):
@@ -483,6 +484,7 @@ class DnfModule(YumDnf):
         os.environ['LANGUAGE'] = os.environ['LANG'] = locale
 
         global dnf
+        global libdnf
         try:
             import dnf
             import dnf.const
@@ -490,6 +492,7 @@ class DnfModule(YumDnf):
             import dnf.package
             import dnf.subject
             import dnf.util
+            import libdnf
             HAS_DNF = True
         except ImportError:
             HAS_DNF = False
@@ -557,6 +560,9 @@ class DnfModule(YumDnf):
         # Load substitutions from the filesystem
         conf.substitutions.update_from_etc(installroot)
 
+        # Substitute variables in cachedir path
+        conf.cachedir = libdnf.conf.ConfigParser.substitute(conf.cachedir, conf.substitutions)
+
         # Handle different DNF versions immutable mutable datatypes and
         # dnf v1/v2/v3
         #

test/lib/ansible_test/_util/controller/sanity/mypy/ansible-core.ini

@@ -58,6 +58,9 @@ ignore_missing_imports = True
 [mypy-dnf.*]
 ignore_missing_imports = True
 
+[mypy-libdnf.*]
+ignore_missing_imports = True
+
 [mypy-apt.*]
 ignore_missing_imports = True
 

test/lib/ansible_test/_util/controller/sanity/mypy/modules.ini

@@ -25,6 +25,9 @@ ignore_missing_imports = True
 [mypy-dnf.*]
 ignore_missing_imports = True
 
+[mypy-libdnf.*]
+ignore_missing_imports = True
+
 [mypy-apt.*]
 ignore_missing_imports = True