# Support for passing complex (nested dictionary) arguments to modules added **URL:** \ **Category:** Ansible Project\ **Created:** [February 17, 2013, 8:16pm UTC](https://forum.ansible.com/t/support-for-passing-complex-nested-dictionary-arguments-to-modules-added/12376 "2013-02-17T20:16:46Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [February 17, 2013, 8:16pm UTC](https://forum.ansible.com/t/support-for-passing-complex-nested-dictionary-arguments-to-modules-added/12376/1 "2013-02-17T20:16:46Z")
Warning -- this a complex topic I'm adding to enable James Martin's work on the Cloud Formations module. If the idea of this seems confusing, you don't have to use it. It will be best illustrated by live examples that use it, rather than the technical example of how it works. What this is -- I've added the ability to specify complex arguments to modules. What does it look like? Here's a really basic example: [https://github.com/ansible/ansible/blob/devel/examples/playbooks/complex\_args.yml](https://github.com/ansible/ansible/blob/devel/examples/playbooks/complex_args.yml) As you notice, this gets more verbose than Ansible normally likes to me. It's there to support those \*complex\* use cases, like the Cloud Formations idea, rather than everyday use cases. It's for when key=value arguments aren't good enough -- which is basically only 1% of the time or something like that. We are still going to prefer the dead-simple "key=value" form, but there are times when passing a complex datastructure is needed. There are a few caveats to usage: (A) If the data structure is complex -- i.e. more than a dictionary of strings, numbers, and booleans -- i.e. a nested data structure -- the module must be written in Python and use the standard ansible module common infrastructure or be an action plugin that knows what to do with these things. This shouldn't be a problem for many people, but just be aware that a Bash module still gets the key=value stuff. This is good actually, because you don't want to be parsing JSON in bash most of the time 🙂 Simple data structures can still be passed to any old standard module, though some clever hacks under the hood, just any members of those hashes that are lists or hashes themselves will not be forwarded along. (B) Right now this only is really working for "normal" remote modules. This means it won't work as a way to feed data to, for example, fetch or pause. This is easy to add and just takes adding a few calls to self.runnner.\_complex\_args\_hack like I have in lib/ansible/runner/action\_plugins/normal.py, and we'll do this. Again, the goal here was to pass those arguments to things like the CloudFormations module, so it didn't seem to be an immediate priority. I'll file a ticket about this just the same, and I'm not documenting this feature just yet for this reason. (C) It is possible to add both the key=value arguments and the extra "args" arguments at the same time. I have coded this so the key=value arguments can win, which provides an extra feature where you can use the "args:" to supply defaults. For instance, you could do, "args: ${file\_defaults}" if you so chose, and it would basically work like you would expect. I think this is not something I would probably do, but it's there, in case you want to do it. (D) In order to support this, the signature of action\_plugins run() method has changed. If you want to save your own custom action plugins from API additions in the future, this is super easy to do, just make sure your plugin ends with run(....,\*\*kwargs) to absorb keyword arguments. If you haven't done this, you will need to make that change. ---
**Author:** ![Tomasz\_Paczkowski](https://avatars.discourse-cdn.com/v4/letter/t/f6c823/32.png) [@Tomasz\_Paczkowski](https://forum.ansible.com/u/Tomasz_Paczkowski)\ **Post date:** [February 18, 2013, 1:35pm UTC](https://forum.ansible.com/t/support-for-passing-complex-nested-dictionary-arguments-to-modules-added/12376/2 "2013-02-18T13:35:08Z")
I’m trying this out. How do I pass complex argument to hacking/test-module? ---
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [February 18, 2013, 2:07pm UTC](https://forum.ansible.com/t/support-for-passing-complex-nested-dictionary-arguments-to-modules-added/12376/3 "2013-02-18T14:07:58Z")
You can't for now, you need to use a playbook. We could tweak that to accept complex args from stdin or something though, maybe with an extra flag? ---
**Author:** ![Tomasz\_Paczkowski](https://avatars.discourse-cdn.com/v4/letter/t/f6c823/32.png) [@Tomasz\_Paczkowski](https://forum.ansible.com/u/Tomasz_Paczkowski)\ **Post date:** [February 18, 2013, 2:12pm UTC](https://forum.ansible.com/t/support-for-passing-complex-nested-dictionary-arguments-to-modules-added/12376/4 "2013-02-18T14:12:54Z")
From stdin or a file would be nice: test-module -m ./module -a spam=good -e - # stdin test-module -m ./module -a spam=good -e ./bacon.{yml|json} ---
**Author:** ![Arne\_Jacobs](https://avatars.discourse-cdn.com/v4/letter/a/9f8e36/32.png) [@Arne\_Jacobs](https://forum.ansible.com/u/Arne_Jacobs)\ **Post date:** [February 22, 2013, 8:54pm UTC](https://forum.ansible.com/t/support-for-passing-complex-nested-dictionary-arguments-to-modules-added/12376/5 "2013-02-22T20:54:58Z")
I find the example quite difficult to read and understand. I wondered why, and I think it’s because the complex variables are not all in strict JSON format. I know, YAML is a superset of JSON, but somehow I think it would be clearer and better to read, if all complex variables would be in JSON format. At last, module output is in JSON, too… Or did I completely misunderstand everything? “defaults” and “complex” are complex variables, right? As is the part after “args:”, but unnamed in that case? I somehow get confused with the keywords looking very similar to variables. Cheers ---
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [February 22, 2013, 9:05pm UTC](https://forum.ansible.com/t/support-for-passing-complex-nested-dictionary-arguments-to-modules-added/12376/6 "2013-02-22T21:05:18Z")
> I find the example quite difficult to read and understand. I wondered why, > and I think it's because the complex variables are not all in strict JSON > format. I know, YAML is a superset of JSON, but somehow I think it would be > clearer and better to read, if all complex variables would be in JSON > format. At last, module output is in JSON, too... Nope, not going to happen. We use YAML for playbooks and things are going to be in YAML. > Or did I completely misunderstand everything? "defaults" and "complex" are > complex variables, right? As is the part after "args:", but unnamed in that > case? I somehow get confused with the keywords looking very similar to > variables. args is a dictionary, always, it may be a dictionary inline or one referenced by a variable ---
**Author:** ![Arne\_Jacobs](https://avatars.discourse-cdn.com/v4/letter/a/9f8e36/32.png) [@Arne\_Jacobs](https://forum.ansible.com/u/Arne_Jacobs)\ **Post date:** [February 22, 2013, 9:45pm UTC](https://forum.ansible.com/t/support-for-passing-complex-nested-dictionary-arguments-to-modules-added/12376/7 "2013-02-22T21:45:11Z")
> Nope, not going to happen. > > We use YAML for playbooks and things are going to be in YAML. Ok, but I guess I could always force myself to keep all complex variables in JSON, right? 😛 > args is a dictionary, always, it may be a dictionary inline or one > referenced by a variable Yes of course, but it is a dictionary which is interpreted by Ansible in a certain way, that's why I think of it as some kind of "keyword". It just confuses me sometimes... is something such a "keyword", i.e. is it expected that way by Ansible (like "args"), or is it expected by a module as an argument (i.e., the module specifies the name), or is it just a variable whose name I am free to choose, as long as I reference it accordingly later (like "complex" in the example) etc... Well, I'm relatively new to YAML, so sorry about the fuss. ---
**Author:** ![Michael\_DeHaan](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@Michael\_DeHaan](https://forum.ansible.com/u/Michael_DeHaan)\ **Post date:** [February 22, 2013, 9:53pm UTC](https://forum.ansible.com/t/support-for-passing-complex-nested-dictionary-arguments-to-modules-added/12376/8 "2013-02-22T21:53:36Z")
> Yes of course, but it is a dictionary which is interpreted by Ansible in a > certain way, that's why I think of it as some kind of "keyword". It's just a dictionary. > It just confuses me sometimes... is something such a "keyword", i.e. is it > expected that way by Ansible (like "args"), or is it expected by a module as > an argument (i.e., the module specifies the name), or is it just a variable > whose name I am free to choose, as long as I reference it accordingly later > (like "complex" in the example) etc... You have to say "args: "