package_manager: fix the DNF4 fallback for --no-bootstrap-chroot

When package_manager = dnf, 'dnf4' is to be selected and used when
bootstrap chroot is disabled.

This was not detected by test-suite; my bet is that we do tests with
testConfig=fedora-40-x86_64 which is already dnf5 and we have dnf5
installed on the testing machines.  I'm trying to modify one test-case
to test DNF4 chroot explicitly.

Fixes: rpm-software-management#1475

mock/integration-tests/23-local-mirrorlist.tst

@@ -35,11 +35,14 @@ gpgcheck=0
 """
 EOF
 
+# default chroot is DNF5, centos-stream is DNF4
+for chroot in "" "-r centos-stream+epel-9-x86_64"; do
 for isolation in simple nspawn; do
-    for bootstrap in bootstrap-chroot no-bootstrap-chroot; do
-        mock="$MOCKCMD --isolation=$isolation  --$bootstrap -r $config"
-        $mock --install always-installable
-        $mock --scrub=chroot
-        $mock --scrub=bootstrap
-    done
+for bootstrap in bootstrap-chroot no-bootstrap-chroot; do
+    mock="$MOCKCMD $chroot --isolation=$isolation  --$bootstrap -r $config"
+    $mock --install always-installable
+    $mock --scrub=chroot
+    $mock --scrub=bootstrap
+done
+done
 done

mock/py/mockbuild/package_manager.py

@@ -19,7 +19,6 @@
 
 fallbacks = {
     'dnf4': ['dnf4', 'dnf5', 'yum'],
-    'dnf': ['dnf4', 'dnf5', 'yum'],  # backward-compat
     'yum': ['yum', 'dnf4', 'dnf5'],
     'microdnf': ['microdnf', 'dnf4', 'dnf5', 'yum'],
     'dnf5': ['dnf5', 'dnf4', 'yum'],
@@ -31,7 +30,7 @@ def package_manager_from_string(name):
         return Dnf5
     if name == 'yum':
         return Yum
-    if name in ['dnf4', 'dnf']:  # dnf for backward compat
+    if name in 'dnf4':
         return Dnf
     if name == 'microdnf':
         return MicroDnf
@@ -54,6 +53,10 @@ def package_manager_exists(pm_class, config_opts, chroot=None):
 
 def package_manager_class_fallback(config_opts, buildroot, fallback):
     desired = config_opts['package_manager']
+
+    if desired == 'dnf':  # backward compat
+        desired = 'dnf4'
+
     if not fallback:
         return package_manager_from_string(desired)
 

releng/release-notes-next/dnf-to-dnf4-fallback-fix.bugfix

@@ -0,0 +1,3 @@
+A fix for the DNF → DNF4 fallback has been applied.  Now Mock correctly selects
+DNF4, even when the `--no-bootstrap-chroot` command is used.  See
+[issue#1475][] for more info.