* Behavior of templating DOS-type text files changes with Ansible v2.
A bug in Ansible v1 causes DOS-type text files (using a carriage return and newline) to be templated to Unix-type text files (using only a newline). In Ansible v2 this long-standing bug was finally fixed and DOS-type text files are preserved correctly. This may be confusing when you expect your playbook to not show any differences when migrating to Ansible v2, while in fact you will see every DOS-type file being completely replaced (with what appears to be the exact same content).
* templating (variables in playbooks and template lookups) has improved with regard to keeping the original instead of turning everything into a string.
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.
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).
* 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.
* 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.
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.::
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 variables to a role invocation.
An issue with the 'bare variable' features, which was supposed only template 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 conditionals (`when`)::
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.
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.
* 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.
..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.
