Fix pacman: "IndexError: list index out of range" ansible#63077 (ansi…

…ble#65750)

* Fix ansible#63077

If the package is already installed the stdout is not as expected by this function. Either remove `--needed` or just noop if we detect pacman returning. We cannot match the stdout string, as that is most likely localized.

```
[root@archBook user]# /usr/bin/pacman --upgrade --noconfirm --noprogressbar --needed  /srv/aur/src/i3cat-git/i3cat-git-r38.c6d29dd-1-x86_64.pkg.tar.xz
loading packages...
warning: i3cat-git-r38.c6d29dd-1 is up to date -- skipping
 there is nothing to do
```

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* Add changelog fragment.

Co-authored-by: Felix Fontein <[email protected]>

changelogs/fragments/65750-pacman.yml

@@ -0,0 +1,2 @@
+bugfixes:
+- "pacman - fix module crash with ``IndexError: list index out of range`` (https://github.com/ansible/ansible/issues/63077)"

lib/ansible/modules/packaging/os/pacman.py

@@ -329,14 +329,17 @@ def install_packages(module, pacman_path, state, packages, package_files):
         if rc != 0:
             module.fail_json(msg="failed to install %s: %s" % (" ".join(to_install_repos), stderr))
 
-        data = stdout.split('\n')[3].split(' ')[2:]
-        data = [i for i in data if i != '']
-        for i, pkg in enumerate(data):
-            data[i] = re.sub('-[0-9].*$', '', data[i].split('/')[-1])
-            if module._diff:
-                diff['after'] += "%s\n" % pkg
-
-        install_c += len(to_install_repos)
+        # As we pass `--needed` to pacman returns a single line of ` there is nothing to do` if no change is performed.
+        # The check for > 3 is here because we pick the 4th line in normal operation.
+        if len(stdout.split('\n')) > 3:
+            data = stdout.split('\n')[3].split(' ')[2:]
+            data = [i for i in data if i != '']
+            for i, pkg in enumerate(data):
+                data[i] = re.sub('-[0-9].*$', '', data[i].split('/')[-1])
+                if module._diff:
+                    diff['after'] += "%s\n" % pkg
+
+            install_c += len(to_install_repos)
 
     if to_install_files:
         cmd = "%s --upgrade --noconfirm --noprogressbar --needed %s %s" % (pacman_path, module.params["extra_args"], " ".join(to_install_files))
@@ -345,14 +348,17 @@ def install_packages(module, pacman_path, state, packages, package_files):
         if rc != 0:
             module.fail_json(msg="failed to install %s: %s" % (" ".join(to_install_files), stderr))
 
-        data = stdout.split('\n')[3].split(' ')[2:]
-        data = [i for i in data if i != '']
-        for i, pkg in enumerate(data):
-            data[i] = re.sub('-[0-9].*$', '', data[i].split('/')[-1])
-            if module._diff:
-                diff['after'] += "%s\n" % pkg
-
-        install_c += len(to_install_files)
+        # As we pass `--needed` to pacman returns a single line of ` there is nothing to do` if no change is performed.
+        # The check for > 3 is here because we pick the 4th line in normal operation.
+        if len(stdout.split('\n')) > 3:
+            data = stdout.split('\n')[3].split(' ')[2:]
+            data = [i for i in data if i != '']
+            for i, pkg in enumerate(data):
+                data[i] = re.sub('-[0-9].*$', '', data[i].split('/')[-1])
+                if module._diff:
+                    diff['after'] += "%s\n" % pkg
+
+            install_c += len(to_install_files)
 
     if state == 'latest' and len(package_err) > 0:
         message = "But could not ensure 'latest' state for %s package(s) as remote version could not be fetched." % (package_err)