Documentation

Documenting Your Module

The online module documentation is generated from the modules themselves. As the module documentation is generated from documentation strings contained in the modules, all modules included with Ansible must have a DOCUMENTATION string. This string must be a valid YAML document which conforms to the schema defined below. You may find it easier to start writing your DOCUMENTATION string in an editor with YAML syntax highlighting before you include it in your Python file.

All modules must have the following sections defined in this order:

  1. ANSIBLE_METADATA
  2. DOCUMENTATION
  3. EXAMPLES
  4. RETURNS
  5. Python imports

Note

Why don’t the imports go first?

Keen Python programmers may notice that contrary to PEP8’s advice we don’t put imports at the top of the file. This is because the ANSIBLE_METADATA through RETURNS sections are not used by the module code itself; they are essentially extra docstrings for the file. The imports are placed after these special variables for the same reason as PEP8 puts the imports after the introductory comments and docstrings. This keeps the active parts of the code together and the pieces which are purely informational apart. The decision to exclude E402 is based on readability (which is what PEP8 is about). Documentation strings in a module are much more similar to module level docstrings, than code, and are never utilized by the module itself. Placing the imports below this documentation and closer to the code, consolidates and groups all related code in a congruent manner to improve readability, debugging and understanding.

Warning

Why do some modules have imports at the bottom of the file?

If you look at some existing older modules, you may find imports at the bottom of the file. Do not copy that idiom into new modules as it is a historical oddity due to how modules used to be combined with libraries. Over time we’re moving the imports to be in their proper place.

ANSIBLE_METADATA Block

ANSIBLE_METADATA contains information about the module for use by other tools. At the moment, it informs other tools which type of maintainer the module has and to what degree users can rely on a module’s behaviour remaining the same over time.

For new modules, the following block can be simply added into your module

ANSIBLE_METADATA = {'metadata_version': '1.0',
                    'status': ['preview'],
                    'supported_by': 'community'}

Warning

  • metadata_version is the version of the ANSIBLE_METADATA schema, not the version of the module.
  • Promoting a module’s status or supported_by status should only be done by members of the Ansible Core Team.

Note

Pre-released metdata version

During development of Ansible-2.3, modules had an initial version of the metadata. This version was modified slightly after release to fix some points of confusion. You may occassionally see PRs for modules where the ANSIBLE_METADATA doesn’t look quite right because of this. Module metadata should be fixed before checking it into the repository.

Version 1.0 of the metadata

Structure

ANSIBLE_METADATA = {
    'metadata_version': '1.0',
    'supported_by': 'community',
    'status': ['preview', 'deprecated']
}

Fields

metadata_version:
 

An “X.Y” formatted string. X and Y are integers which define the metadata format version. Modules shipped with Ansible are tied to an Ansible release, so we will only ship with a single version of the metadata. We’ll increment Y if we add fields or legal values to an existing field. We’ll increment X if we remove fields or values or change the type or meaning of a field.

supported_by:

This field records who supports the module. Default value is community. Values are:

core:
curated:
community:

For information on what the support level values entail, please see Modules Support.

status:

This field records information about the module that is important to the end user. It’s a list of strings. The default value is a single element list [“preview”]. The following strings are valid statuses and have the following meanings:

stableinterface:
 This means that the module’s parameters are stable. Every effort will be made not to remove parameters or change their meaning. It is not a rating of the module’s code quality.
preview:This module is a tech preview. This means it may be unstable, the parameters may change, or it may require libraries or web services that are themselves subject to incompatible changes.
deprecated:This module is deprecated and will no longer be available in a future release.
removed:This module is not present in the release. A stub is kept so that documentation can be built. The documentation helps users port from the removed module to new modules.

DOCUMENTATION Block

See an example documentation string in the checkout under examples/DOCUMENTATION.yml.

Include it in your module file like this:

#!/usr/bin/python
# Copyright header....

DOCUMENTATION = '''
---
module: modulename
short_description: This is a sentence describing the module
# ... snip ...
'''

The following fields can be used and are all required unless specified otherwise:

module:

The name of the module. This must be the same as the filename, without the .py extension.

short_description:
 
  • A short description which is displayed on the All Modules page and ansible-doc -l.
  • As the short description is displayed by ansible-doc -l without the category grouping it needs enough detail to explain its purpose without the context of the directory structure in which it lives.
  • Unlike description: this field should not have a trailing full stop.
description:
  • A detailed description (generally two or more sentences).
  • Must be written in full sentences, i.e. with capital letters and fullstops.
  • Shouldn’t mention the name module.
version_added:

The version of Ansible when the module was added. This is a string, and not a float, i.e. version_added: "2.1"

author:

Name of the module author in the form First Last (@GitHubID). Use a multi-line list if there is more than one author.

deprecated:

If this module is deprecated, detail when that happened, and what to use instead, e.g. Deprecated in 2.3. Use M(whatmoduletouseinstead) instead. Ensure CHANGELOG.md is updated to reflect this.

options:

One per module argument:

option-name:
  • Declarative operation (not CRUD)–this makes it easy for a user not to care what the existing state is, just about the final state, for example online:, rather than is_online:.
  • The name of the option should be consistent with the rest of the module, as well as other modules in the same category.
description:
  • Detailed explanation of what this option does. It should be written in full sentences.
  • Should not list the options values (that’s what choices: is for, though it should explain what the values do if they aren’t obvious.
  • If an optional parameter is sometimes required this need to be reflected in the documentation, e.g. “Required when I(state=present).”
  • Mutually exclusive options must be documented as the final sentence on each of the options.
required:

Only needed if true, otherwise it is assumed to be false.

default:
  • If required is false/missing, default may be specified (assumed ‘null’ if missing).
  • Ensure that the default parameter in the docs matches the default parameter in the code.
  • The default option must not be listed as part of the description.
choices:

List of option values. Should be absent if empty.

type:

If an argument is type='bool', this field should be set to type: bool and no choices should be specified.

aliases:

List of option name aliases; generally not needed.

version_added:

Only needed if this option was extended after initial Ansible release, i.e. this is greater than the top level version_added field. This is a string, and not a float, i.e. version_added: "2.3".

suboptions:

If this option takes a dict, you can define it here. See azure_rm_securitygroup, os_ironic_node for examples.

requirements:

List of requirements, and minimum versions (if applicable)

notes:

Details of any important information that doesn’t fit in one of the above sections; for example if check_mode isn’t supported, or a link to external documentation.

Note

  • The above fields are are all in lowercase.
  • If the module doesn’t doesn’t have any options (for example, it’s a _facts module), you can use options: {}.

EXAMPLES block

The EXAMPLES section is required for all new modules.

Examples should demonstrate real world usage, and be written in multi-line plain-text YAML format.

Ensure that examples are kept in sync with the options during the PR review and any following code refactor.

As per playbook best practice, a name: should be specified.

EXAMPLES string within the module like this:

EXAMPLES = '''
- name: Ensure foo is installed
  modulename:
    name: foo
    state: present
'''

If the module returns facts that are often needed, an example of how to use them can be helpful.

RETURN Block

The RETURN section documents what the module returns, and is required for all new modules.

For each value returned, provide a description, in what circumstances the value is returned, the type of the value and a sample. For example, from the copy module:

The following fields can be used and are all required unless specified otherwise.

return name:

Name of the returned field.

description:

Detailed description of what this value represents.

returned:

When this value is returned, such as always, on success, always

type:

Data type

sample:

One or more examples.

contains:

Optional, if you set type: complex you can detail the dictionary here by repeating the above elements.

return name:

One per return

description:Detailed description of what this value represents.
returned:When this value is returned, such as always, on success, always
type:Data type
sample:One or more examples.

For complex nested returns type can be specified as type: complex.

Example:

RETURN = '''
dest:
    description: destination file/path
    returned: success
    type: string
    sample: /path/to/file.txt
src:
    description: source file used for the copy on the target machine
    returned: changed
    type: string
    sample: /home/httpd/.ansible/tmp/ansible-tmp-1423796390.97-147729857856000/source
md5sum:
    description: md5 checksum of the file after running copy
    returned: when supported
    type: string
    sample: 2a5aeecc61dc98c4d780b14b330e3282
...

Note

If your module doesn’t return anything (apart from the standard returns), you can use RETURN = ''' # '''.

Python Imports

Starting with Ansible version 2.2, all new modules are required to use imports in the form:

from module_utils.basic import AnsibleModule

Warning

The use of “wildcard” imports such as from module_utils.basic import * is no longer allowed.

Formatting options

These formatting functions are U() for URLs, I() for option names, C() for files and option values and M() for module names. Module names should be specified as M(module) to create a link to the online documentation for that module.

Example usage:

Or if not set the environment variable C(ACME_PASSWORD) will be used.
...
Required if I(state=present)
...
Mutually exclusive with I(project_src) and I(files).
...
See also M(win_copy) or M(win_template).
...
See U(https://www.ansible.com/tower) for an overview.

Note

If you wish to refer a collection of modules, use C(..), e.g. Refer to the C(win_*) modules.

Documentation fragments

Some categories of modules share common documentation, such as details on how to authenticate options, or file mode settings. Rather than duplicate that information it can be shared using docs_fragments.

These shared fragments are similar to the standard documentation block used in a module, they are just contained in a ModuleDocFragment class.

All the existing docs_fragments can be found in lib/ansible/utils/module_docs_fragments/.

To include, simply add in extends_documentation_fragment: FRAGMENT_NAME into your module.

Examples can be found by searching for extends_documentation_fragment under the Ansible source tree.

Testing documentation

Put your completed module file into the lib/ansible/modules/$CATEGORY/ directory and then run the command: make webdocs. The new ‘modules.html’ file will be built in the docs/docsite/_build/html/$MODULENAME_module.html directory.

To test your documentation against your argument_spec you can use validate-modules. Note that this option isn’t currently enabled in Shippable due to the time it takes to run.

# If you don't already, ensure you are using your local checkout
source hacking/env-setup
./test/sanity/validate-modules/validate-modules --arg-spec --warnings  lib/ansible/modules/your/modules/

Tip

If you’re having a problem with the syntax of your YAML you can validate it on the YAML Lint website.

For more information in testing, including how to add unit and integration tests, see Testing Ansible.