ansible/docsite/rst/porting_guide_2.0.rst

Porting Guide
=============


Playbook
--------

* backslash escapes When specifying parameters in jinja2 expressions in YAML
  dicts, backslashes sometimes needed to be escaped twice. This has been fixed
  in 2.0.x so that escaping once works. The following example shows how
  playbooks must be modified::

    # Syntax in 1.9.x
    - debug:
        msg: "{{ 'test1_junk 1\\\\3' | regex_replace('(.*)_junk (.*)', '\\\\1 \\\\2') }}"
    # Syntax in 2.0.x
    - debug:
        msg: "{{ 'test1_junk 1\\3' | regex_replace('(.*)_junk (.*)', '\\1 \\2') }}"

    # Output:
    "msg": "test1 1\\3"

To make an escaped string that will work on all versions you have two options::

- debug: msg="{{ 'test1_junk 1\\3' | regex_replace('(.*)_junk (.*)', '\\1 \\2') }}"

uses key=value escaping which has not changed.  The other option is to check for the ansible version::

"{{ (ansible_version|version_compare('ge', '2.0'))|ternary( 'test1_junk 1\\3' | regex_replace('(.*)_junk (.*)', '\\1 \\2') , 'test1_junk 1\\\\3' | regex_replace('(.*)_junk (.*)', '\\\\1 \\\\2') ) }}"

* trailing newline When a string with a trailing newline was specified in the
  playbook via yaml dict format, the trailing newline was stripped. When
  specified in key=value format, the trailing newlines were kept. In v2, both
  methods of specifying the string will keep the trailing newlines. If you
  relied on the trailing newline being stripped, you can change your playbook
  using the following as an example::

    # Syntax in 1.9.x
    vars:
      message: >
        Testing
        some things
    tasks:
    - debug:
        msg: "{{ message }}"

    # Syntax in 2.0.x
    vars:
      old_message: >
        Testing
        some things
      message: "{{ old_messsage[:-1] }}"
    - debug:
        msg: "{{ message }}"
    # Output
    "msg": "Testing some things"

* When specifying complex args as a variable, the variable must use the full jinja2
  variable syntax (```{{var_name}}```) - bare variable names there are no longer accepted.
  In fact, even specifying args with variables has been deprecated, and will not be
  allowed in future versions::

    ---
    - hosts: localhost
      connection: local
      gather_facts: false
      vars:
        my_dirs:
          - { path: /tmp/3a, state: directory, mode: 0755 }
          - { path: /tmp/3b, state: directory, mode: 0700 }
      tasks:
        - file:
          args: "{{item}}" # <- args here uses the full variable syntax
          with_items: "{{my_dirs}}"

* porting task includes
* More dynamic. Corner-case formats that were not supposed to work now do not, as expected.
* variables defined in the yaml dict format https://github.com/ansible/ansible/issues/13324
* templating (variables in playbooks and template lookups) has improved with regard to keeping the original instead of turning everything into a string.
  If you need the old behavior, quote the value to pass it around as a string.
* Empty variables and variables set to null in yaml are no longer converted to empty strings. They will retain the value of `None`.
  You can override the `null_representation` setting to an empty string in your config file by setting the `ANSIBLE_NULL_REPRESENTATION` environment variable.
* Extras callbacks must be whitelisted in ansible.cfg. Copying is no longer necessary but whitelisting in ansible.cfg must be completed.
* dnf module has been rewritten. Some minor changes in behavior may be observed.
* win_updates has been rewritten and works as expected now.
* from 2.0.1 onwards, the implicit setup task from gather_facts now correctly inherits everything from play, but this might cause issues for those setting
  `environment` at the play level and depending on `ansible_env` existing. Previouslly this was ignored but now might issue an 'Undefined' error.

Deprecated
----------

While all items listed here will show a deprecation warning message, they still work as they did in 1.9.x. Please note that they will be removed in 2.2 (Ansible always waits two major releases to remove a deprecated feature).

* Bare variables in `with_` loops should instead use the “{{var}}” syntax, which helps eliminate ambiguity.
* The ansible-galaxy text format requirements file. Users should use the YAML format for requirements instead.
* Undefined variables within a `with_` loop’s list currently do not interrupt the loop, but they do issue a warning; in the future, they will issue an error.
* Using dictionary variables to set all task parameters is unsafe and will be removed in a future version. For example::

    - hosts: localhost
      gather_facts: no
      vars:
        debug_params:
          msg: "hello there"
      tasks:
        # These are both deprecated:
        - debug: "{{debug_params}}"
        - debug:
          args: "{{debug_params}}"

        # Use this instead:
        - debug:
            msg: "{{debug_params['msg']}}"

* Host patterns should use a comma (,) or colon (:) instead of a semicolon (;) to separate hosts/groups in the pattern.
* Ranges specified in host patterns should use the [x:y] syntax, instead of [x-y].
* Playbooks using privilege escalation should always use “become*” options rather than the old su*/sudo* options.
* The “short form” for vars_prompt is no longer supported.
  For example::

    vars_prompt:
        variable_name: "Prompt string"

* Specifying variables at the top level of a task include statement is no longer supported. For example::

    - include: foo.yml
        a: 1

Should now be::

    - include: foo.yml
      vars:
        a: 1

* Setting any_errors_fatal on a task is no longer supported. This should be set at the play level only.
* Bare variables in the `environment` dictionary (for plays/tasks/etc.) are no longer supported. Variables specified there should use the full variable syntax: ‘{{foo}}’.
* Tags (or any directive) should no longer be specified with other parameters in a task include. Instead, they should be specified as an option on the task.
  For example::

    - include: foo.yml tags=a,b,c

  Should be::

    - include: foo.yml
      tags: [a, b, c]

* The first_available_file option on tasks has been deprecated. Users should use the with_first_found option or lookup (‘first_found’, …) plugin.


Other caveats
-------------

Here are some corner cases encountered when updating, these are mostly caused by the more stringent parser validation and the capture of errors that were previouslly ignored.

* Bad variable composition::

    with_items: myvar_{{rest_of_name}}

  This worked 'by accident' as the errors were retemplated and ended up resolving the variable, it was never intended as valid syntax and now properly returns an error, use the following instead.::

    with_items: "{{vars['myvar_' + res_of_name]}}"

  Or `hostvars[inventory_hostname]['myvar_' + rest_of_name]` if appropriate.

* Misspelled directives::

    - task: dostuf
      becom: yes

  The task always ran without using privilege escalation (for that you need `become`) but was also silently ignored so the play 'ran' even though it should not, now this is a parsing error.


* Duplicate directives::

    - task: dostuf
      when: True
      when: False

  The first `when` was ignored and only the 2nd one was used as the play ran w/o warning it was ignoring one of the directives, now this produces a parsing error.

* Conflating variables and directives::

    - role: {name=rosy, port=435 }

    # in tasks/main.yml
    - wait_for: port={{port}}

  The `port` variable is reserved as a play/task directive for overriding the connection port, in previous versions this got conflated with a variable named `port` and was usable
  later in the play, this created issues if a host tried to reconnect or was using a non caching connection. Now it will be correctly identified as a directive and the `port` variable
  will appear as undefined, this now forces the use of non conflicting names and removes ambiguity when adding settings and varaibles to a role invocation..

* Bare operations on `with_`::

    with_items: var1 + var2

  An issue with the 'bare variable' features, which was supposed only tempate a single variable without the need of braces ({{ )}}, would in some versions of Ansible template full expressions.
  Now you need to use proper templating and braces for all expressions everywhere except condtionals (`when`)::

    with_items: "{{var1 + var2}}"

  The bare feature itself is deprecated as an undefined variable is indistiguishable from a string which makes it difficult to display a proper error.

Porting plugins
===============

In ansible-1.9.x, you would generally copy an existing plugin to create a new one. Simply implementing the methods and attributes that the caller of the plugin expected made it a plugin of that type. In ansible-2.0, most plugins are implemented by subclassing a base class for each plugin type. This way the custom plugin does not need to contain methods which are not customized.


Lookup plugins
--------------
* lookup plugins ; import version


Connection plugins
------------------

* connection plugins

Action plugins
--------------

* action plugins

Callback plugins
----------------

Although Ansible 2.0 provides a new callback API the old one continues to work
for most callback plugins.  However, if your callback plugin makes use of
:attr:`self.playbook`, :attr:`self.play`, or :attr:`self.task` then you will
have to store the values for these yourself as ansible no longer automatically
populates the callback with them.  Here's a short snippet that shows you how::

    from ansible.plugins.callback import CallbackBase

    class CallbackModule(CallbackBase):
        def __init__(self):
            self.playbook = None
            self.play = None
            self.task = None

        def v2_playbook_on_start(self, playbook):
            self.playbook = playbook

        def v2_playbook_on_play_start(self, play):
            self.play = play

        def v2_playbook_on_task_start(self, task, is_conditional):
            self.task = task

        def v2_on_any(self, *args, **kwargs):
            self._display.display('%s: %s: %s' % (self.playbook.name,
            self.play.name, self.task))


Connection plugins
------------------

* connection plugins


Hybrid plugins
==============
In specific cases you may want a plugin that supports both ansible-1.9.x *and* ansible-2.0. Much like porting plugins from v1 to v2, you need to understand how plugins work in each version and support both requirements. It may mean playing tricks on Ansible.

Since the ansible-2.0 plugin system is more advanced, it is easier to adapt your plugin to provide similar pieces (subclasses, methods) for ansible-1.9.x as ansible-2.0 expects. This way your code will look a lot cleaner.

You may find the following tips useful:

* Check whether the ansible-2.0 class(es) are available and if they are missing (ansible-1.9.x) mimic them with the needed methods (e.g. ``__init__``)

* When ansible-2.0 python modules are imported, and they fail (ansible-1.9.x), catch the ``ImportError`` exception and perform the equivalent imports for ansible-1.9.x. With possible translations (e.g. importing specific methods).

* Use the existence of these methods as a qualifier to what version of Ansible you are running. So rather than using version checks, you can do capability checks instead. (See examples below)

* Document for each if-then-else case for which specific version each block is needed. This will help others to understand how they have to adapt their plugins, but it will also help you to remove the older ansible-1.9.x support when it is deprecated.

* When doing plugin development, it is very useful to have the ``warning()`` method during development, but it is also important to emit warnings for deadends (cases that you expect should never be triggered) or corner cases (e.g. cases where you expect misconfigurations).

* It helps to look at other plugins in ansible-1.9.x and ansible-2.0 to understand how the API works and what modules, classes and methods are available.


Lookup plugins
--------------
As a simple example we are going to make a hybrid ``fileglob`` lookup plugin.  The ``fileglob`` lookup plugin is pretty simple to understand::

    from __future__ import (absolute_import, division, print_function)
    __metaclass__ = type

    import os
    import glob

    try:
        # ansible-2.0
        from ansible.plugins.lookup import LookupBase
    except ImportError:
        # ansible-1.9.x

        class LookupBase(object):
            def __init__(self, basedir=None, runner=None, **kwargs):
                self.runner = runner
                self.basedir = self.runner.basedir

            def get_basedir(self, variables):
                return self.basedir

    try:
        # ansible-1.9.x
        from ansible.utils import (listify_lookup_plugin_terms, path_dwim, warning)
    except ImportError:
        # ansible-2.0
        from __main__ import display
        warning = display.warning

    class LookupModule(LookupBase):

        # For ansible-1.9.x, we added inject=None as valid argument
        def run(self, terms, inject=None, variables=None, **kwargs):

            # ansible-2.0, but we made this work for ansible-1.9.x too !
            basedir = self.get_basedir(variables)

            # ansible-1.9.x
            if 'listify_lookup_plugin_terms' in globals():
                terms = listify_lookup_plugin_terms(terms, basedir, inject)

            ret = []
            for term in terms:
                term_file = os.path.basename(term)

                # For ansible-1.9.x, we imported path_dwim() from ansible.utils
                if 'path_dwim' in globals():
                    # ansible-1.9.x
                    dwimmed_path = path_dwim(basedir, os.path.dirname(term))
                else:
                    # ansible-2.0
                    dwimmed_path = self._loader.path_dwim_relative(basedir, 'files', os.path.dirname(term))

                globbed = glob.glob(os.path.join(dwimmed_path, term_file))
                ret.extend(g for g in globbed if os.path.isfile(g))

            return ret

.. Note:: In the above example we did not use the ``warning()`` method as we had no direct use for it in the final version. However we left this code in so people can use this part during development/porting/use.



Connection plugins
------------------

* connection plugins

Action plugins
--------------

* action plugins

Callback plugins
----------------

* callback plugins

Connection plugins
------------------

* connection plugins


Porting custom scripts
======================

Custom scripts that used the ``ansible.runner.Runner`` API in 1.x have to be ported in 2.x.  Please refer to:
https://github.com/ansible/ansible/blob/devel/docsite/rst/developing_api.rst