Allow map filter to retrieve multiple items

[Yannik]

At the moment, the map function can only be used like this:

[{'path':'/var/file1', 'mtime': '123', 'mode': '600',...},{'path':'/var/file2', 'mtime': '123', 'mode': 644, ...}]|map(attribute='path')

with the return of

['/var/file1', '/var/file2']

(Docs: http://jinja.pocoo.org/docs/dev/templates/#map)

I want to propose allowing this:

[{'path':'/var/file1', 'mtime': '123', 'mode': '600',...},{'path':'/var/file2', 'mtime': '123', 'mode': 644, ...}]|map(attribute=['path', 'mtime'])

or

[{'path':'/var/file1', 'mtime': '123', 'mode': '600',...},{'path':'/var/file2', 'mtime': '123', 'mode': 644, ...}]|map(attributes=['path', 'mtime'])

which should return

[{'path':'/var/file1', 'mtime': '123'},{'path':'/var/file2', 'mtime': '123'}]

You can already see what this is useful for: manipulating a list of dicts so that these dicts only retain a limited set of attributes.

[ssenaria]

Would LOVE this feature.

[davidism]

I'm not clear why this is needed in templates. Just iterating over the dictionaries and using the attributes you need will accomplish the same thing. If you need different data, it's probably a better idea to do that manipulation in Python before rendering. I could maybe see a use for it returning tuples.

[Nee6ione]

If anyone still needs this you can use the following code (put in playbooks/filter_plugins/mapattributes.py):

#!/usr/bin/env python
class FilterModule(object):
  def filters(self):
    return { 'mapattributes': self.mapattributes }

  def mapattributes(self, list_of_dicts, list_of_keys):
    l = []
    for di in list_of_dicts:
      newdi = { }
      for key in list_of_keys:
        newdi[key] = di[key]
      l.append(newdi)
    return l

Use via:

ansible_mounts | mapattributes(['mount', 'size_total', 'size_available',])