Module format and documentation

If you want to contribute your module to most Ansible collections, you must write your module in Python and follow the standard format described below. (Unless you’re writing a Windows module, in which case the Windows guidelines apply.) In addition to following this format, you should review our submission checklist, programming tips, and strategy for maintaining Python 2 and Python 3 compatibility, as well as information about testing before you open a pull request.

Every Ansible module written in Python must begin with seven standard sections in a particular order, followed by the code. The sections in order are:

Note

Why don’t the imports go first?

Keen Python programmers may notice that contrary to PEP 8’s advice we don’t put imports at the top of the file. This is because the DOCUMENTATION through RETURN 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 PEP 8 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 PEP 8 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

Copy old modules with care!

Some older Ansible modules have imports at the bottom of the file, Copyright notices with the full GPL prefix, and/or DOCUMENTATION fields in the wrong order. These are legacy files that need updating - do not copy them into new modules. Over time we are updating and correcting older modules. Please follow the guidelines on this page!

Python shebang & UTF-8 coding

Begin your Ansible module with #!/usr/bin/python - this “shebang” allows ansible_python_interpreter to work. Follow the shebang immediately with # -*- coding: utf-8 -*- to clarify that the file is UTF-8 encoded.

ANSIBLE_METADATA block

Since we moved to collections we have deprecated the METADATA functionality, it is no longer required for modules, but it will not break anything if present.

DOCUMENTATION block

After the shebang, the UTF-8 coding, the copyright line, and the license section comes the DOCUMENTATION block. Ansible’s online module documentation is generated from the DOCUMENTATION blocks in each module’s source code. The DOCUMENTATION block must be valid YAML. 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. You can start by copying our example documentation string into your module file and modifying it. If you run into syntax issues in your YAML, you can validate it on the YAML Lint website.

Module documentation should briefly and accurately define what each module and option does, and how it works with others in the underlying system. Documentation should be written for broad audience–readable both by experts and non-experts.

  • Descriptions should always start with a capital letter and end with a full stop. Consistency always helps.

  • Verify that arguments in doc and module spec dict are identical.

  • For password / secret arguments no_log=True should be set.

  • For arguments that seem to contain sensitive information but do not contain secrets, such as “password_length”, set no_log=False to disable the warning message.

  • If an option is only sometimes required, describe the conditions. For example, “Required when I(state=present).”

  • If your module allows check_mode, reflect this fact in the documentation.

To create clear, concise, consistent, and useful documentation, follow the style guide.

Each documentation field is described below. Before committing your module documentation, please test it at the command line and as HTML:

  • As long as your module file is available locally, you can use ansible-doc -t module my_module_name to view your module documentation at the command line. Any parsing errors will be obvious - you can view details by adding -vvv to the command.

  • You should also test the HTML output of your module documentation.

Documentation fields

All fields in the DOCUMENTATION block are lower-case. All fields are required unless specified otherwise:

module

  • The name of the module.

  • Must be the same as the filename, without the .py extension.

short_description

  • A short description which is displayed on the Collection Index page and ansible-doc -l.

  • The short_description is displayed by ansible-doc -l without any category grouping, so it needs enough detail to explain the module’s purpose without the context of the directory structure in which it lives.

  • Unlike description:, short_description should not have a trailing period/full stop.

description

  • A detailed description (generally two or more sentences).

  • Must be written in full sentences, in other words, with capital letters and periods/full stops.

  • Shouldn’t mention the module name.

  • Make use of multiple entries rather than using one long paragraph.

  • Don’t quote complete values unless it is required by YAML.

version_added

  • The version of Ansible when the module was added.

  • This is a string, and not a float, for example, version_added: '2.1'.

  • In collections, this must be the collection version the module was added to, not the Ansible version. For example, version_added: 1.0.0.

author

  • Name of the module author in the form First Last (@GitHubID).

  • Use a multi-line list if there is more than one author.

  • Don’t use quotes as it should not be required by YAML.

deprecated
options

  • Options are often called parameters or arguments. Because the documentation field is called options, we will use that term.

  • If the module has no options (for example, it’s a _facts module), all you need is one line: options: {}.

  • If your module has options (in other words, accepts arguments), each option should be documented thoroughly. For each module option, include:

option-name

  • Declarative operation (not CRUD), to focus on 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.

  • When in doubt, look for other modules to find option names that are used for the same purpose, we like to offer consistency to our users.

description

  • Detailed explanation of what this option does. It should be written in full sentences.

  • The first entry is a description of the option itself; subsequent entries detail its use, dependencies, or format of possible values.

  • Should not list the possible values (that’s what choices: is for, though it should explain what the values do if they aren’t obvious).

  • If an option is only sometimes required, describe the conditions. For example, “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.

  • If missing, we assume the option is not required.

default

  • If required is false/missing, default may be specified (assumed ‘null’ if missing).

  • Ensure that the default value in the docs matches the default value in the code.

  • The default field must not be listed as part of the description, unless it requires additional information or conditions.

  • If the option is a boolean value, you can use any of the boolean values recognized by Ansible: (such as true/false or yes/no). Choose the one that reads better in the context of the option.

choices

  • List of option values.

  • Should be absent if empty.

type

  • Specifies the data type that option accepts, must match the argspec.

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

  • If an argument is type='list', elements should be specified.

elements

  • Specifies the data type for list elements in case type='list'.

aliases

  • List of optional name aliases.

  • Generally not needed.

version_added

  • Only needed if this option was extended after initial Ansible release, in other words, this is greater than the top level version_added field.

  • This is a string, and not a float, for example, version_added: '2.3'.

  • In collections, this must be the collection version the option was added to, not the Ansible version. For example, version_added: 1.0.0.

suboptions
requirements

  • List of requirements (if applicable).

  • Include minimum versions.

seealso

  • A list of references to other modules, documentation or Internet resources

  • In Ansible 2.10 and later, references to modules must use the FQCN or ansible.builtin for modules in ansible-core.

  • A reference can be one of the following formats:

    seealso:

# Reference by module name
- module: cisco.aci.aci_tenant

# Reference by module name, including description
- module: cisco.aci.aci_tenant
  description: ACI module to create tenants on a Cisco ACI fabric.

# Reference by rST documentation anchor
- ref: aci_guide
  description: Detailed information on how to manage your ACI infrastructure using Ansible.

# Reference by Internet resource
- name: APIC Management Information Model reference
  description: Complete reference of the APIC object model.
  link: https://developer.cisco.com/docs/apic-mim-ref/
notes

  • Details of any important information that doesn’t fit in one of the above sections.

  • For example, whether check_mode is or is not supported.

Linking and other format macros within module documentation

You can link from your module documentation to other module docs, other resources on docs.ansible.com, and resources elsewhere on the internet with the help of some pre-defined macros. The correct formats for these macros are:

  • L() for links with a heading. For example: See L(Ansible Automation Platform,https://www.ansible.com/products/automation-platform). As of Ansible 2.10, do not use L() for relative links between Ansible documentation and collection documentation.

  • U() for URLs. For example: See U(https://www.ansible.com/products/automation-platform) for an overview.

There are also some macros which do not create links but we use them to display certain types of content in a uniform way:

  • I() for option names. For example: Required if I(state=present). This is italicized in the documentation.

  • C() for files, option values, and inline code. For example: If not set the environment variable C(ACME_PASSWORD) will be used. or Use C(var | foo.bar.my_filter) to transform C(var) into the required format. This displays with a mono-space font in the documentation.

  • B() currently has no standardized usage. It is displayed in boldface in the documentation.

  • HORIZONTALLINE is used sparingly as a separator in long descriptions. It becomes a horizontal rule (the <hr> html tag) in the documentation.

Note

For links between modules and documentation within a collection, you can use either of the options above. Use U() or L() with full URLs (not relative links).

Note

  • When a collection is not the right granularity, use C(..):

    • The C(win_*) modules (spread across several collections) allow you to manage various aspects of windows hosts.

Note

Because it stands out better, use seealso for general references over the use of notes or adding links to the description.

Documentation fragments

If you are writing multiple related modules, they may share common documentation, such as authentication details, file mode settings, notes: or seealso: entries. Rather than duplicate that information in each module’s DOCUMENTATION block, you can save it once as a doc_fragment plugin and use it in each module’s documentation. In Ansible, shared documentation fragments are contained in a ModuleDocFragment class in lib/ansible/plugins/doc_fragments/ or the equivalent directory in a collection. To include a documentation fragment, add extends_documentation_fragment: FRAGMENT_NAME in your module documentation. Use the fully qualified collection name for the FRAGMENT_NAME (for example, kubernetes.core.k8s_auth_options).

Modules should only use items from a doc fragment if the module will implement all of the interface documented there in a manner that behaves the same as the existing modules which import that fragment. The goal is that items imported from the doc fragment will behave identically when used in another module that imports the doc fragment.

By default, only the DOCUMENTATION property from a doc fragment is inserted into the module documentation. It is possible to define additional properties in the doc fragment in order to import only certain parts of a doc fragment or mix and match as appropriate. If a property is defined in both the doc fragment and the module, the module value overrides the doc fragment.

Here is an example doc fragment named example_fragment.py:

class ModuleDocFragment(object):
    # Standard documentation
    DOCUMENTATION = r'''
    options:
      # options here
    '''

    # Additional section
    OTHER = r'''
    options:
      # other options here
    '''

To insert the contents of OTHER in a module:

extends_documentation_fragment: example_fragment.other

Or use both :

extends_documentation_fragment:
  - example_fragment
  - example_fragment.other

New in version 2.8.

Since Ansible 2.8, you can have user-supplied doc_fragments by using a doc_fragments directory adjacent to play or role, just like any other plugin.

For example, all AWS modules should include:

extends_documentation_fragment:
- aws
- ec2

Using documentation fragments in collections describes how to incorporate documentation fragments in a collection.

EXAMPLES block

After the shebang, the UTF-8 coding, the copyright line, the license section, and the DOCUMENTATION block comes the EXAMPLES block. Here you show users how your module works with real-world examples in multi-line plain-text YAML format. The best examples are ready for the user to copy and paste into a playbook. Review and update your examples with every change to your module.

Per playbook best practices, each example should include a name: line:

EXAMPLES = r'''
- name: Ensure foo is installed
  namespace.collection.modulename:
    name: foo
    state: present
'''

The name: line should be capitalized and not include a trailing dot.

Use a fully qualified collection name (FQCN) as a part of the module’s name like in the example above. For modules in ansible-core, use the ansible.builtin. identifier, for example ansible.builtin.debug.

If your examples use boolean options, use yes/no values. Since the documentation generates boolean values as yes/no, having the examples use these values as well makes the module documentation more consistent.

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

RETURN block

After the shebang, the UTF-8 coding, the copyright line, the license section, DOCUMENTATION and EXAMPLES blocks comes the RETURN block. This section documents the information the module returns for use by other modules.

If your module doesn’t return anything (apart from the standard returns), this section of your module should read: RETURN = r''' # ''' Otherwise, for each value returned, provide the following fields. All fields are required unless specified otherwise.

return name

Name of the returned field.

description

Detailed description of what this value represents. Capitalized and with trailing dot.

returned

When this value is returned, such as always, changed or success. This is a string and can contain any human-readable content.

type

Data type.

elements

If type='list', specifies the data type of the list’s elements.

sample

One or more examples.

version_added

Only needed if this return was extended after initial Ansible release, in other words, this is greater than the top level version_added field. This is a string, and not a float, for example, version_added: '2.3'.

contains

Optional. To describe nested return values, set type: dict, or type: list/elements: dict, or if you really have to, type: complex, and repeat the elements above for each sub-field.

Here are two example RETURN sections, one with three simple fields and one with a complex nested field:

RETURN = r'''
dest:
    description: Destination file/path.
    returned: success
    type: str
    sample: /path/to/file.txt
src:
    description: Source file used for the copy on the target machine.
    returned: changed
    type: str
    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: str
    sample: 2a5aeecc61dc98c4d780b14b330e3282
'''

RETURN = r'''
packages:
    description: Information about package requirements.
    returned: success
    type: dict
    contains:
        missing:
            description: Packages that are missing from the system.
            returned: success
            type: list
            elements: str
            sample:
                - libmysqlclient-dev
                - libxml2-dev
        badversion:
            description: Packages that are installed but at bad versions.
            returned: success
            type: list
            elements: dict
            sample:
                - package: libxml2-dev
                  version: 2.9.4+dfsg1-2
                  constraint: ">= 3.0"
'''

Python imports

After the shebang, the UTF-8 coding, the copyright line, the license, and the sections for DOCUMENTATION, EXAMPLES, and RETURN, you can finally add the python imports. All modules must use Python imports in the form:

from module_utils.basic import AnsibleModule

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

Testing module documentation

To test Ansible documentation locally please follow instruction.