In this section, we will walk through developing, testing, and debugging an
Ansible Windows module.
Because Windows modules are written in Powershell and need to be run on a
Windows host, this guide differs from the usual development walkthrough guide.
What's covered in this section:
..contents:: Topics
Windows environment setup
=========================
TODO: Add in more information on how to use Vagrant to setup a Windows host.
Windows new module development
==============================
When creating a new module there are a few things to keep in mind:
- Module code is in Powershell (.ps1) files while the documentation is contained in Python (.py) files of the same name
- Avoid using ``Write-Host/Debug/Verbose/Error`` in the module and add what needs to be returned to the ``$result`` variable
- When trying an exception use ``Fail-Json -obj $result -message "exception message here"`` instead
- Most new modules require check mode and integration tests before they are merged into the main Ansible codebase
- Avoid using try/catch statements over a large code block, rather use them for individual calls so the error message can be more descriptive
- Try and catch specific exceptions when using try/catch statements
- Avoid using PSCustomObjects unless necessary
- Look for common functions in ``./lib/ansible/module_utils/powershell/`` and use the code there instead of duplicating work. These can be imported by adding the line ``#Requires -Module *`` where * is the filename to import, and will be automatically included with the module code sent to the Windows target when run via Ansible
- Ensure the code runs under Powershell v3 and higher on Windows Server 2008 and higher; if higher minimum Powershell or OS versions are required, ensure the documentation reflects this clearly
- Ansible runs modules under strictmode version 2.0. Be sure to test with that enabled by putting ``Set-StrictMode -Version 2.0`` at the top of your dev script
- Favour native Powershell cmdlets over executable calls if possible
- If adding an object to ``$result``, ensure any trailing slashes are removed or escaped, as ``ConvertTo-Json`` will fail to convert it
- Use the full cmdlet name instead of aliases, e.g. ``Remove-Item`` over ``rm``
- Use named parameters with cmdlets, e.g. ``Remove-Item -Path C:\temp`` over ``Remove-Item C:\temp``
A very basic powershell module `win_environment <https://github.com/ansible/ansible/blob/devel/lib/ansible/modules/windows/win_environment.ps1>`_ is included below. It demonstrates how to implement check-mode and diff-support, and also shows a warning to the user when a specific condition is met.
A slightly more advanced module is `win_uri <https://github.com/ansible/ansible/blob/devel/lib/ansible/modules/windows/win_uri.ps1>`_ which additionally shows how to use different parameter types (bool, str, int, list, dict, path) and a selection of choices for parameters, how to fail a module and how to handle exceptions.
PowerShell modules support a small subset of the ``#Requires`` options built
into PowerShell as well as some Ansible-specific requirements specified by
``#AnsibleRequires``. These statements can be placed at any point in the script,
but are most commonly near the top. They are used to make it easier to state the
requirements of the module without writing any of the checks. Each ``requires``
statement must be on its own line, but there can be multiple requires statements
in one script.
These are the checks that can be used within Ansible modules:
-``#Requires -Module Ansible.ModuleUtils.<module_util>``: Added in Ansible 2.4, specifies a module_util to load in for the module execution.
-``#Requires -Version x.y``: Added in Ansible 2.5, specifies the version of PowerShell that is required by the module. The module will fail if this requirement is not met.
-``#AnsibleRequires -OSVersion x.y``: Added in Ansible 2.5, specifies the OS build version that is required by the module and will fail if this requirement is not met. The actual OS version is derived from ``[Environment]::OSVersion.Version``.
-``#AnsibleRequires -Become``: Added in Ansible 2.5, forces the exec runner to run the module with ``become``, which is primarily used to bypass WinRM restrictions. If ``ansible_become_user`` is not specified then the ``SYSTEM`` account is used instead.
Windows module utilities
========================
Like Python modules, PowerShell modules also provide a number of module
utilities that provide helper functions within PowerShell. These module_utils
can be imported by adding the following line to a PowerShell module:
..code-block:: powershell
#Requires -Module Ansible.ModuleUtils.Legacy
This will import the module_util at ``./lib/ansible/module_utils/powershell/Ansible.ModuleUtils.Legacy.psm1``
and enable calling all of its functions.
The following is a list of module_utils that are packaged with Ansible and a general description of what
they do:
- ArgvParser: Utiliy used to convert a list of arguments to an escaped string compliant with the Windows argument parsing rules.
- CamelConversion: Utility used to convert camelCase strings/lists/dicts to snake_case.
- CommandUtil: Utility used to execute a Windows process and return the stdout/stderr and rc as separate objects.
- Legacy: General definitions and helper utilities for Ansible module.
- SID: Utilities used to convert a user or group to a Windows SID and vice versa.
For more details on any specific module utility and their requirements, please see the `Ansible
- To stop the script from exiting the editor on a successful run, in ``Ansible.ModuleUtils.Legacy.psm1`` under the function ``Exit-Json``, replace the last two lines of the function with::
- To stop the script from exiting the editor on a failed run, in ``Ansible.ModuleUtils.Legacy.psm1`` under the function ``Fail-Json``, replace the last two lines of the function with::
- Prefix the Ansible command with :envvar:`ANSIBLE_KEEP_REMOTE_FILES=1` to specify that Ansible should keep the exec files on the server.
- Log onto the Windows server using the same user account that Ansible used to execute the module.
- Navigate to ``%TEMP%\..``. It should contain a folder starting with ``ansible-tmp-``.
- Inside this folder, open the PowerShell script for the module.
- In this script is a raw JSON script under ``$json_raw`` which contains the module arguments under ``module_args``. These args can be assigned manually to the ``$complex_args`` variable that is defined on your debug script.
