Executive summary: skipping a host corrupts a variable (when it is registered)
We have a play existing out of multiple tasks that check a condition, if one of these tasks fails we want to skip all next tasks in the playbook. I noticed that if we skip a task because a certain condition is met, and this task has a register-attribute, I loose the value in the variable. Which means we cannot use that variable in subsequent tasks to evaluate because it was skipped:
```
- action: command test -d /some/directory
register: task
- action: command test -f /some/directory/file
register: task
only_if: '${task.rc} == 0'
- action: do something else
only_if: '${task.rc} == 0'
```
In the above example, if the second task is skipped (because the first failed), the third action will end with a "SyntaxError: invalid syntax" complaining about the unsubstituted ${task.rc} (even though it was set by the first task and used for skipping the second).
The following play demonstrates the problem:
```
- name: Test register on ignored tasks
hosts: all
gather_facts: no
vars:
skip: true
task: { 'rc': 666 }
tasks:
- action: debug msg='skip = ${skip}, task.rc = ${task.rc}'
- name: Skip this task, just to test if task has changed
action: command ls
register: task
only_if: '${skip} != True'
- action: debug msg='skip = ${skip}, task.rc = ${task.rc}'
- name: Now use task value
action: command echo 'Works !'
only_if: '${task.rc} == 0'
```
And the enclosed fix, fixes the above problem.
After spending 10 minutes to find which playbook had an action/local_action missing, I changed the error to include the task name (if set). The error eventually was caused because I added a name to a task, but the dash before the existing action was not removed.
We now check explicitely for 'module_setup' in the SETUP_CACHE in order to avoid skipping setup because SETUP_CACHE was populated some other way. Other modules can implement the same mechanism to test if they've already run.
This closes#1206.
This change makes a distinction between no_hosts_matched and no_hosts_remaining.
In both cases we do not start facts-gathering, or run any tasks.
In the case that there are no more hosts remaining, we abort running tasks and abort the playbook.
I also cleaned up the leftovers from the previous patchsets, as these are no longer required.
This closes#1187.
Example playbook:
```yaml
---
- hosts: emptygroup
tasks:
- action: command date
- action: command false
- hosts: all
gather_facts: False
tasks:
- action: command ls
- action: command false
- action: command true
- hosts: all
tasks:
- action: command true
- action: command false
- hosts: all
tasks:
- action: command pwd
```
