Add path_join compatibility shim (#2172)

* Add path_join compatibility shim.

* Add myself as maintainer.

.github/BOTMETA.yml

@@ -59,6 +59,8 @@ files:
     maintainers: kellyjonbrazil
   $filters/list.py:
     maintainers: vbotka
+  $filters/path_join_shim.py:
+    maintainers: felixfontein
   $filters/time.py:
     maintainers: resmo
   $httpapis/:

changelogs/fragments/path_join-shim-filter.yml

@@ -0,0 +1,3 @@
+add plugin.filter:
+  - name: path_join
+    description: Redirects to ansible.builtin.path_join for ansible-base 2.10 or newer, and provides a compatible implementation for Ansible 2.9

meta/runtime.yml

@@ -611,3 +611,10 @@ plugin_routing:
       redirect: community.docker.docker_swarm
     kubevirt:
       redirect: community.kubevirt.kubevirt
+  filter:
+    path_join:
+      # The ansible.builtin.path_join filter has been added in ansible-base 2.10.
+      # Since plugin routing is only available since ansible-base 2.10, this
+      # redirect will be used for ansible-base 2.10 or later, and the included
+      # path_join filter will be used for Ansible 2.9 or earlier.
+      redirect: ansible.builtin.path_join

plugins/filter/path_join_shim.py

@@ -0,0 +1,28 @@
+# -*- coding: utf-8 -*-
+
+# Copyright: (c) 2020-2021, Felix Fontein <felix@fontein.de>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import absolute_import, division, print_function
+__metaclass__ = type
+
+
+import os.path
+
+
+def path_join(list):
+    '''Join list of paths.
+
+    This is a minimal shim for ansible.builtin.path_join included in ansible-base 2.10.
+    This should only be called by Ansible 2.9 or earlier. See meta/runtime.yml for details.
+    '''
+    return os.path.join(*list)
+
+
+class FilterModule(object):
+    '''Ansible jinja2 filters'''
+
+    def filters(self):
+        return {
+            'path_join': path_join,
+        }

tests/integration/targets/filter_path_join_shim/aliases

@@ -0,0 +1,2 @@
+shippable/posix/group1
+skip/python2.6  # filters are controller only, and we no longer support Python 2.6 on the controller

tests/integration/targets/filter_path_join_shim/tasks/main.yml

@@ -0,0 +1,7 @@
+---
+- name: "Test path_join filter"
+  assert:
+    that:
+      - "['a', 'b'] | community.general.path_join == 'a/b'"
+      - "['a', '/b'] | community.general.path_join == '/b'"
+      - "[''] | community.general.path_join == ''"