Added filter plugin lists_mergeby. Fix #249 (#604)

changelogs/fragments/604-lists_mergeby-new-filter.yml

@@ -0,0 +1,23 @@
+---
+minor_changes:
+  - |
+    A new filter ``lists_mergeby`` to merge two lists of dictionaries by an attribute.
+    For example:
+
+    .. code-block:: yaml
+
+        [{'n': 'n1', 'p1': 'A', 'p2': 'F'},
+         {'n': 'n2', 'p2': 'B'}] | community.general.lists_mergeby(
+        [{'n': 'n1', 'p1': 'C'},
+         {'n': 'n2', 'p2': 'D'},
+         {'n': 'n3', 'p3': 'E'}], 'n') | list
+
+    evaluates to
+
+    .. code-block:: yaml
+
+        [{'n': 'n1', 'p1': 'C', 'p2': 'F'},
+         {'n': 'n2', 'p2': 'D'},
+         {'n': 'n3', 'p3': 'E'}]
+
+    (https://github.com/ansible-collections/community.general/pull/604).

plugins/filter/list.py

@@ -0,0 +1,47 @@
+# -*- coding: utf-8 -*-
+# Copyright (c) 2020, Vladimir Botka <vbotka@gmail.com>
+# 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
+
+from ansible.errors import AnsibleError, AnsibleFilterError
+from ansible.module_utils.six import string_types
+from ansible.module_utils.common._collections_compat import Mapping, Sequence
+from collections import defaultdict
+from operator import itemgetter
+
+
+def lists_mergeby(l1, l2, index):
+    ''' merge lists by attribute index. Example:
+        - debug: msg="{{ l1|community.general.lists_mergeby(l2, 'index')|list }}" '''
+
+    if not isinstance(l1, Sequence):
+        raise AnsibleFilterError('First argument for community.general.lists_mergeby must be list. %s is %s' %
+                                 (l1, type(l1)))
+
+    if not isinstance(l2, Sequence):
+        raise AnsibleFilterError('Second argument for community.general.lists_mergeby must be list. %s is %s' %
+                                 (l2, type(l2)))
+
+    if not isinstance(index, string_types):
+        raise AnsibleFilterError('Third argument for community.general.lists_mergeby must be string. %s is %s' %
+                                 (index, type(index)))
+
+    d = defaultdict(dict)
+    for l in (l1, l2):
+        for elem in l:
+            if not isinstance(elem, Mapping):
+                raise AnsibleFilterError('Elements of list arguments for lists_mergeby must be dictionaries. Found {0!r}.'.format(elem))
+            if index in elem.keys():
+                d[elem[index]].update(elem)
+    return sorted(d.values(), key=itemgetter(index))
+
+
+class FilterModule(object):
+    ''' Ansible list filters '''
+
+    def filters(self):
+        return {
+            'lists_mergeby': lists_mergeby,
+        }

tests/integration/targets/filter_list/aliases

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+shippable/posix/group2
+skip/python2.6  # filters are controller only, and we no longer support Python 2.6 on the controller

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

@@ -0,0 +1,6 @@
+---
+- name: Test lists merged by attribute name
+  assert:
+    that:
+      - "(list1 | community.general.lists_mergeby(list2, 'name') | list |
+          difference(list3) | length) == 0"

tests/integration/targets/filter_list/vars/main.yml

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+list1:
+  - name: myname01
+    param01: myparam01
+  - name: myname02
+    param01: myparam02
+
+list2:
+  - name: myname01
+    param01: myparam03
+  - name: myname02
+    param02: myparam04
+  - name: myname03
+    param03: myparam03
+
+list3:
+  - name: myname01
+    param01: myparam03
+  - name: myname02
+    param01: myparam02
+    param02: myparam04
+  - name: myname03
+    param03: myparam03