Add filter docs (#2680)

* Began with filter docs.

* Add more filters.

* Add time unit filters.

* Add TOC and filters to create identifiers.

* Add more filters.

* Add documentation from ansible/ansible for json_query and random_mac.

* Update docs/docsite/rst/filter_guide.rst

Co-authored-by: Abhijeet Kasurde <akasurde@redhat.com>

Co-authored-by: Abhijeet Kasurde <akasurde@redhat.com>

docs/docsite/extra-docs.yml

@@ -0,0 +1,5 @@
+---
+sections:
+  - title: Guides
+    toctree:
+      - filter_guide

docs/docsite/rst/filter_guide.rst

@@ -0,0 +1,753 @@
+.. _ansible_collections.community.general.docsite.filter_guide:
+
+community.general Filter Guide
+==============================
+
+The :ref:`community.general collection <plugins_in_community.general>` offers several useful filter plugins.
+
+.. contents:: Topics
+
+Paths
+-----
+
+The ``path_join`` filter has been added in ansible-base 2.10. If you want to use this filter, but also need to support Ansible 2.9, you can use ``community.general``'s ``path_join`` shim, ``community.general.path_join``. This filter redirects to ``path_join`` for ansible-base 2.10 and ansible-core 2.11 or newer, and re-implements the filter for Ansible 2.9.
+
+.. code-block:: yaml+jinja
+
+    # ansible-base 2.10 or newer:
+    path: {{ ('/etc', path, 'subdir', file) | path_join }}
+
+    # Also works with Ansible 2.9:
+    path: {{ ('/etc', path, 'subdir', file) | community.general.path_join }}
+
+.. versionadded:: 3.0.0
+
+Abstract transformations
+------------------------
+
+Dictionaries
+^^^^^^^^^^^^
+
+You can use the ``dict_kv`` filter to create a single-entry dictionary with ``value | community.general.dict_kv(key)``:
+
+.. code-block:: yaml+jinja
+
+    - name: Create a single-entry dictionary
+      debug:
+        msg: "{{ myvar | community.general.dict_kv('thatsmyvar') }}"
+      vars:
+        myvar: myvalue
+
+    - name: Create a list of dictionaries where the 'server' field is taken from a list
+      debug:
+        msg: >-
+          {{ myservers | map('community.general.dict_kv', 'server')
+                       | map('combine', common_config) }}
+      vars:
+        common_config:
+          type: host
+          database: all
+        myservers:
+        - server1
+        - server2
+
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Create a single-entry dictionary]  **************************************************
+    ok: [localhost] => {
+        "msg": {
+            "thatsmyvar": "myvalue"
+        }
+    }
+
+    TASK [Create a list of dictionaries where the 'server' field is taken from a list]  *******
+    ok: [localhost] => {
+        "msg": [
+            {
+                "database": "all",
+                "server": "server1",
+                "type": "host"
+            },
+            {
+                "database": "all",
+                "server": "server2",
+                "type": "host"
+            }
+        ]
+    }
+
+.. versionadded:: 2.0.0
+
+If you need to convert a list of key-value pairs to a dictionary, you can use the ``dict`` function. Unfortunately, this function cannot be used with ``map``. For this, the ``community.general.dict`` filter can be used:
+
+.. code-block:: yaml+jinja
+
+    - name: Create a dictionary with the dict function
+      debug:
+        msg: "{{ dict([[1, 2], ['a', 'b']]) }}"
+
+    - name: Create a dictionary with the community.general.dict filter
+      debug:
+        msg: "{{ [[1, 2], ['a', 'b']] | community.general.dict }}"
+
+    - name: Create a list of dictionaries with map and the community.general.dict filter
+      debug:
+        msg: >-
+          {{ values | map('zip', ['k1', 'k2', 'k3'])
+                    | map('map', 'reverse')
+                    | map('community.general.dict') }}
+      vars:
+        values:
+          - - foo
+            - 23
+            - a
+          - - bar
+            - 42
+            - b
+
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Create a dictionary with the dict function]  ****************************************
+    ok: [localhost] => {
+        "msg": {
+            "1": 2,
+            "a": "b"
+        }
+    }
+
+    TASK [Create a dictionary with the community.general.dict filter]  ************************
+    ok: [localhost] => {
+        "msg": {
+            "1": 2,
+            "a": "b"
+        }
+    }
+
+    TASK [Create a list of dictionaries with map and the community.general.dict filter]  ******
+    ok: [localhost] => {
+        "msg": [
+            {
+                "k1": "foo",
+                "k2": 23,
+                "k3": "a"
+            },
+            {
+                "k1": "bar",
+                "k2": 42,
+                "k3": "b"
+            }
+        ]
+    }
+
+.. versionadded:: 3.0.0
+
+Grouping
+^^^^^^^^
+
+If you have a list of dictionaries, the Jinja2 ``groupby`` filter allows to group the list by an attribute. This results in a list of ``(grouper, list)`` namedtuples, where ``list`` contains all dictionaries where the selected attribute equals ``grouper``. If you know that for every ``grouper``, there will be a most one entry in that list, you can use the ``community.general.groupby_as_dict`` filter to convert the original list into a dictionary which maps ``grouper`` to the corresponding dictionary.
+
+One example is ``ansible_facts.mounts``, which is a list of dictionaries where each has one ``device`` element to indicate the device which is mounted. Therefore, ``ansible_facts.mounts | community.general.groupby_as_dict('device')`` is a dictionary mapping a device to the mount information:
+
+.. code-block:: yaml+jinja
+
+    - name: Output mount facts grouped by device name
+      debug:
+        var: ansible_facts.mounts | community.general.groupby_as_dict('device')
+
+    - name: Output mount facts grouped by mount point
+      debug:
+        var: ansible_facts.mounts | community.general.groupby_as_dict('mount')
+
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Output mount facts grouped by device name] ******************************************
+    ok: [localhost] => {
+        "ansible_facts.mounts | community.general.groupby_as_dict('device')": {
+            "/dev/sda1": {
+                "block_available": 2000,
+                "block_size": 4096,
+                "block_total": 2345,
+                "block_used": 345,
+                "device": "/dev/sda1",
+                "fstype": "ext4",
+                "inode_available": 500,
+                "inode_total": 512,
+                "inode_used": 12,
+                "mount": "/boot",
+                "options": "rw,relatime,data=ordered",
+                "size_available": 56821,
+                "size_total": 543210,
+                "uuid": "ab31cade-d9c1-484d-8482-8a4cbee5241a"
+            },
+            "/dev/sda2": {
+                "block_available": 1234,
+                "block_size": 4096,
+                "block_total": 12345,
+                "block_used": 11111,
+                "device": "/dev/sda2",
+                "fstype": "ext4",
+                "inode_available": 1111,
+                "inode_total": 1234,
+                "inode_used": 123,
+                "mount": "/",
+                "options": "rw,relatime",
+                "size_available": 42143,
+                "size_total": 543210,
+                "uuid": "abcdef01-2345-6789-0abc-def012345678"
+            }
+        }
+    }
+
+    TASK [Output mount facts grouped by mount point] ******************************************
+    ok: [localhost] => {
+        "ansible_facts.mounts | community.general.groupby_as_dict('mount')": {
+            "/": {
+                "block_available": 1234,
+                "block_size": 4096,
+                "block_total": 12345,
+                "block_used": 11111,
+                "device": "/dev/sda2",
+                "fstype": "ext4",
+                "inode_available": 1111,
+                "inode_total": 1234,
+                "inode_used": 123,
+                "mount": "/",
+                "options": "rw,relatime",
+                "size_available": 42143,
+                "size_total": 543210,
+                "uuid": "bdf50b7d-4859-40af-8665-c637ee7a7808"
+            },
+            "/boot": {
+                "block_available": 2000,
+                "block_size": 4096,
+                "block_total": 2345,
+                "block_used": 345,
+                "device": "/dev/sda1",
+                "fstype": "ext4",
+                "inode_available": 500,
+                "inode_total": 512,
+                "inode_used": 12,
+                "mount": "/boot",
+                "options": "rw,relatime,data=ordered",
+                "size_available": 56821,
+                "size_total": 543210,
+                "uuid": "ab31cade-d9c1-484d-8482-8a4cbee5241a"
+            }
+        }
+    }
+
+.. versionadded: 3.0.0
+
+Merging lists of dictionaries
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+If you have two lists of dictionaries and want to combine them into a list of merged dictionaries, where two dictionaries are merged if they coincide in one attribute, you can use the ``lists_mergeby`` filter.
+
+.. code-block:: yaml+jinja
+
+    - name: Merge two lists by common attribute 'name'
+      debug:
+        var: list1 | community.general.lists_mergeby(list2, 'name')
+      vars:
+        list1:
+          - name: foo
+            extra: true
+          - name: bar
+            extra: false
+          - name: meh
+            extra: true
+        list2:
+          - name: foo
+            path: /foo
+          - name: baz
+            path: /bazzz
+
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Merge two lists by common attribute 'name']  ****************************************
+    ok: [localhost] => {
+        "list1 | community.general.lists_mergeby(list2, 'name')": [
+            {
+                "extra": false,
+                "name": "bar"
+            },
+            {
+                "name": "baz",
+                "path": "/bazzz"
+            },
+            {
+                "extra": true,
+                "name": "foo",
+                "path": "/foo"
+            },
+            {
+                "extra": true,
+                "name": "meh"
+            }
+        ]
+    }
+
+.. versionadded: 2.0.0
+
+Working with times
+------------------
+
+The ``to_time_unit`` filter allows to convert times from a human-readable string to a unit. For example, ``'4h 30min 12second' | community.general.to_time_unit('hour')`` gives the number of hours that correspond to 4 hours, 30 minutes and 12 seconds.
+
+There are shorthands to directly convert to various units, like ``to_hours``, ``to_minutes``, ``to_seconds``, and so on. The following table lists all units that can be used:
+
+.. list-table:: Units
+   :widths: 25 25 25 25
+   :header-rows: 1
+
+   * - Unit name
+     - Unit value in seconds
+     - Unit strings for filter
+     - Shorthand filter
+   * - Millisecond
+     - 1/1000 second
+     - ``ms``, ``millisecond``, ``milliseconds``, ``msec``, ``msecs``, ``msecond``, ``mseconds``
+     - ``to_milliseconds``
+   * - Second
+     - 1 second
+     - ``s``, ``sec``, ``secs``, ``second``, ``seconds``
+     - ``to_seconds``
+   * - Minute
+     - 60 seconds
+     - ``m``, ``min``, ``mins``, ``minute``, ``minutes``
+     - ``to_minutes``
+   * - Hour
+     - 60*60 seconds
+     - ``h``, ``hour``, ``hours``
+     - ``to_hours``
+   * - Day
+     - 24*60*60 seconds
+     - ``d``, ``day``, ``days``
+     - ``to_days``
+   * - Week
+     - 7*24*60*60 seconds
+     - ``w``, ``week``, ``weeks``
+     - ``to_weeks``
+   * - Month
+     - 30*24*60*60 seconds
+     - ``mo``, ``month``, ``months``
+     - ``to_months``
+   * - Year
+     - 365*24*60*60 seconds
+     - ``y``, ``year``, ``years``
+     - ``to_years``
+
+Note that months and years are using a simplified representation: a month is 30 days, and a year is 365 days. If you need different definitions of months or years, you can pass them as keyword arguments. For example, if you want a year to be 365.25 days, and a month to be 30.5 days, you can write ``'11months 4' | community.general.to_years(year=365.25, month=30.5)``. These keyword arguments can be specified to ``to_time_unit`` and to all shorthand filters.
+
+.. code-block:: yaml+jinja
+
+    - name: Convert string to seconds
+      debug:
+        msg: "{{ '30h 20m 10s 123ms' | community.general.to_time_unit('seconds') }}"
+
+    - name: Convert string to hours
+      debug:
+        msg: "{{ '30h 20m 10s 123ms' | community.general.to_hours }}"
+
+    - name: Convert string to years (using 365.25 days == 1 year)
+      debug:
+        msg: "{{ '400d 15h' | community.general.to_years(year=365.25) }}"
+
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Convert string to seconds] **********************************************************
+    ok: [localhost] => {
+        "msg": "109210.123"
+    }
+
+    TASK [Convert string to hours] ************************************************************
+    ok: [localhost] => {
+        "msg": "30.336145277778"
+    }
+
+    TASK [Convert string to years (using 365.25 days == 1 year)] ******************************
+    ok: [localhost] => {
+        "msg": "1.096851471595"
+    }
+
+.. versionadded: 0.2.0
+
+Working with versions
+---------------------
+
+If you need to sort a list of version numbers, the Jinja ``sort`` filter is problematic. Since it sorts lexicographically, ``2.10`` will come before ``2.9``. To treat version numbers correctly, you can use the ``version_sort`` filter:
+
+.. code-block:: yaml+jinja
+
+    - name: Sort list by version number
+      debug:
+        var: ansible_versions | community.general.version_sort
+      vars:
+        ansible_versions:
+          - '2.8.0'
+          - '2.11.0'
+          - '2.7.0'
+          - '2.10.0'
+          - '2.9.0'
+
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Sort list by version number] ********************************************************
+    ok: [localhost] => {
+        "ansible_versions | community.general.version_sort": [
+            "2.7.0",
+            "2.8.0",
+            "2.9.0",
+            "2.10.0",
+            "2.11.0"
+        ]
+    }
+
+.. versionadded: 2.2.0
+
+Creating identifiers
+--------------------
+
+The following filters allow to create identifiers.
+
+Hashids
+^^^^^^^
+
+`Hashids <https://hashids.org/>`_ allow to convert sequences of integers to short unique string identifiers. This filter needs the `hashids Python library <https://pypi.org/project/hashids/>`_ installed on the controller.
+
+.. code-block:: yaml+jinja
+
+    - name: "Create hashid"
+      debug:
+        msg: "{{ [1234, 5, 6] | community.general.hashids_encode }}"
+
+    - name: "Decode hashid"
+      debug:
+        msg: "{{ 'jm2Cytn' | community.general.hashids_decode }}"
+
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Create hashid] **********************************************************************
+    ok: [localhost] => {
+        "msg": "jm2Cytn"
+    }
+
+    TASK [Decode hashid] **********************************************************************
+    ok: [localhost] => {
+        "msg": [
+            1234,
+            5,
+            6
+        ]
+    }
+
+The hashids filters accept keyword arguments to allow fine-tuning the hashids generated:
+
+:salt: String to use as salt when hashing.
+:alphabet: String of 16 or more unique characters to produce a hash.
+:min_length: Minimum length of hash produced.
+
+.. versionadded: 3.0.0
+
+Random MACs
+^^^^^^^^^^^
+
+You can use the ``random_mac`` filter to complete a partial `MAC address <https://en.wikipedia.org/wiki/MAC_address>`_ to a random 6-byte MAC address.
+
+.. code-block:: yaml+jinja
+
+    - name: "Create a random MAC starting with ff:"
+      debug:
+        msg: "{{ 'FF' | community.general.random_mac }}"
+
+    - name: "Create a random MAC starting with 00:11:22:"
+      debug:
+        msg: "{{ '00:11:22' | community.general.random_mac }}"
+  
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Create a random MAC starting with ff:] **********************************************
+    ok: [localhost] => {
+        "msg": "ff:69:d3:78:7f:b4"
+    }
+
+    TASK [Create a random MAC starting with 00:11:22:] ****************************************
+    ok: [localhost] => {
+        "msg": "00:11:22:71:5d:3b"
+    }
+
+You can also initialize the random number generator from a seed to create random-but-idempotent MAC addresses:
+
+.. code-block:: yaml+jinja
+
+    "{{ '52:54:00' | community.general.random_mac(seed=inventory_hostname) }}"
+
+Conversions
+-----------
+
+Parsing CSV files
+^^^^^^^^^^^^^^^^^
+
+Ansible offers the :ref:`community.general.read_csv module <ansible_collections.community.general.read_csv_module>` to read CSV files. Sometimes you need to convert strings to CSV files instead. For this, the ``from_csv`` filter exists.
+
+.. code-block:: yaml+jinja
+
+    - name: "Parse CSV from string"
+      debug:
+        msg: "{{ csv_string | community.general.from_csv }}"
+      vars:
+        csv_string: |
+          foo,bar,baz
+          1,2,3
+          you,this,then
+
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Parse CSV from string] **************************************************************
+    ok: [localhost] => {
+        "msg": [
+            {
+                "bar": "2",
+                "baz": "3",
+                "foo": "1"
+            },
+            {
+                "bar": "this",
+                "baz": "then",
+                "foo": "you"
+            }
+        ]
+    }
+
+The ``from_csv`` filter has several keyword arguments to control its behavior:
+
+:dialect: Dialect of the CSV file. Default is ``excel``. Other possible choices are ``excel-tab`` and ``unix``. If one of ``delimiter``, ``skipinitialspace`` or ``strict`` is specified, ``dialect`` is ignored.
+:fieldnames: A set of column names to use. If not provided, the first line of the CSV is assumed to contain the column names.
+:delimiter: Sets the delimiter to use. Default depends on the dialect used.
+:skipinitialspace: Set to ``true`` to ignore space directly after the delimiter. Default depends on the dialect used (usually ``false``).
+:strict: Set to ``true`` to error out on invalid CSV input.
+
+.. versionadded: 3.0.0
+
+Converting to JSON
+^^^^^^^^^^^^^^^^^^
+
+`JC <https://pypi.org/project/jc/>`_ is a CLI tool and Python library which allows to interpret output of various CLI programs as JSON. It is also available as a filter in community.general. This filter needs the `jc Python library <https://pypi.org/project/jc/>`_ installed on the controller.
+
+.. code-block:: yaml+jinja
+
+    - name: Run 'ls' to list files in /
+      command: ls /
+      register: result
+
+    - name: Parse the ls output
+      debug:
+        msg: "{{ result.stdout | community.general.jc('ls') }}"
+
+This produces:
+
+.. code-block:: ansible-output
+
+    TASK [Run 'ls' to list files in /] ********************************************************
+    changed: [localhost]
+
+    TASK [Parse the ls output] ****************************************************************
+    ok: [localhost] => {
+        "msg": [
+            {
+                "filename": "bin"
+            },
+            {
+                "filename": "boot"
+            },
+            {
+                "filename": "dev"
+            },
+            {
+                "filename": "etc"
+            },
+            {
+                "filename": "home"
+            },
+            {
+                "filename": "lib"
+            },
+            {
+                "filename": "proc"
+            },
+            {
+                "filename": "root"
+            },
+            {
+                "filename": "run"
+            },
+            {
+                "filename": "tmp"
+            }
+        ]
+    }
+
+.. versionadded: 2.0.0
+
+.. _ansible_collections.community.general.docsite.json_query_filter:
+
+Selecting JSON data: JSON queries
+---------------------------------
+
+To select a single element or a data subset from a complex data structure in JSON format (for example, Ansible facts), use the ``json_query`` filter.  The ``json_query`` filter lets you query a complex JSON structure and iterate over it using a loop structure.
+
+.. note:: You must manually install the **jmespath** dependency on the Ansible controller before using this filter. This filter is built upon **jmespath**, and you can use the same syntax. For examples, see `jmespath examples <http://jmespath.org/examples.html>`_.
+
+Consider this data structure:
+
+.. code-block:: yaml+jinja
+
+    {
+        "domain_definition": {
+            "domain": {
+                "cluster": [
+                    {
+                        "name": "cluster1"
+                    },
+                    {
+                        "name": "cluster2"
+                    }
+                ],
+                "server": [
+                    {
+                        "name": "server11",
+                        "cluster": "cluster1",
+                        "port": "8080"
+                    },
+                    {
+                        "name": "server12",
+                        "cluster": "cluster1",
+                        "port": "8090"
+                    },
+                    {
+                        "name": "server21",
+                        "cluster": "cluster2",
+                        "port": "9080"
+                    },
+                    {
+                        "name": "server22",
+                        "cluster": "cluster2",
+                        "port": "9090"
+                    }
+                ],
+                "library": [
+                    {
+                        "name": "lib1",
+                        "target": "cluster1"
+                    },
+                    {
+                        "name": "lib2",
+                        "target": "cluster2"
+                    }
+                ]
+            }
+        }
+    }
+
+To extract all clusters from this structure, you can use the following query:
+
+.. code-block:: yaml+jinja
+
+    - name: Display all cluster names
+      ansible.builtin.debug:
+        var: item
+      loop: "{{ domain_definition | community.general.json_query('domain.cluster[*].name') }}"
+
+To extract all server names:
+
+.. code-block:: yaml+jinja
+
+    - name: Display all server names
+      ansible.builtin.debug:
+        var: item
+      loop: "{{ domain_definition | community.general.json_query('domain.server[*].name') }}"
+
+To extract ports from cluster1:
+
+.. code-block:: yaml+jinja
+
+    - name: Display all ports from cluster1
+      ansible.builtin.debug:
+        var: item
+      loop: "{{ domain_definition | community.general.json_query(server_name_cluster1_query) }}"
+      vars:
+        server_name_cluster1_query: "domain.server[?cluster=='cluster1'].port"
+
+.. note:: You can use a variable to make the query more readable.
+
+To print out the ports from cluster1 in a comma separated string:
+
+.. code-block:: yaml+jinja
+
+    - name: Display all ports from cluster1 as a string
+      ansible.builtin.debug:
+        msg: "{{ domain_definition | community.general.json_query('domain.server[?cluster==`cluster1`].port') | join(', ') }}"
+
+.. note:: In the example above, quoting literals using backticks avoids escaping quotes and maintains readability.
+
+You can use YAML `single quote escaping <https://yaml.org/spec/current.html#id2534365>`_:
+
+.. code-block:: yaml+jinja
+
+    - name: Display all ports from cluster1
+      ansible.builtin.debug:
+        var: item
+      loop: "{{ domain_definition | community.general.json_query('domain.server[?cluster==''cluster1''].port') }}"
+
+.. note:: Escaping single quotes within single quotes in YAML is done by doubling the single quote.
+
+To get a hash map with all ports and names of a cluster:
+
+.. code-block:: yaml+jinja
+
+    - name: Display all server ports and names from cluster1
+      ansible.builtin.debug:
+        var: item
+      loop: "{{ domain_definition | community.general.json_query(server_name_cluster1_query) }}"
+      vars:
+        server_name_cluster1_query: "domain.server[?cluster=='cluster2'].{name: name, port: port}"
+
+To extract ports from all clusters with name starting with 'server1':
+
+.. code-block:: yaml+jinja
+
+    - name: Display all ports from cluster1
+      ansible.builtin.debug:
+        msg: "{{ domain_definition | to_json | from_json | community.general.json_query(server_name_query) }}"
+      vars:
+        server_name_query: "domain.server[?starts_with(name,'server1')].port"
+
+To extract ports from all clusters with name containing 'server1':
+
+.. code-block:: yaml+jinja
+
+    - name: Display all ports from cluster1
+      ansible.builtin.debug:
+        msg: "{{ domain_definition | to_json | from_json | community.general.json_query(server_name_query) }}"
+      vars:
+        server_name_query: "domain.server[?contains(name,'server1')].port"
+
+.. note:: while using ``starts_with`` and ``contains``, you have to use `` to_json | from_json `` filter for correct parsing of data structure.