# How do I get a module to work with --diff? **URL:** \ **Category:** Ansible Developer\ **Created:** [January 22, 2016, 4:40pm UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318 "2016-01-22T16:40:05Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Tobias\_Wolf](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tobias\_Wolf](https://forum.ansible.com/u/Tobias_Wolf)\ **Post date:** [January 22, 2016, 4:40pm UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/1 "2016-01-22T16:40:05Z")
So, I want to get --diff to output something useful when using the synchronize module. As I understand it so far, making a diff for changes entails returning a list of ‘before’ and ‘after’ pairs in result[‘diff’]. These contain the two texts that are actually diffed using python difflib. What if I have a “diff” already (e.g. rsync --itemize-changes or rsync --out-format=‘%i %n%L’)? Do I just “print”, or “display.display()” something in case --diff is on? I supposed that isn’t going to get merged if I do it like that. ---
**Author:** ![Brian\_Coca](https://avatars.discourse-cdn.com/v4/letter/b/6de8d8/32.png) [@Brian\_Coca](https://forum.ansible.com/u/Brian_Coca)\ **Post date:** [January 23, 2016, 3:27am UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/2 "2016-01-23T03:27:21Z")
In current devel (future 2.1.0) modules can check module.\_diff boolean property to figure out if they are in diff mode or not, returning a dictionary with the differences keyed to 'diff' will automatically be used by the default callbacks to display it. ---
**Author:** ![Tobias\_Wolf](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tobias\_Wolf](https://forum.ansible.com/u/Tobias_Wolf)\ **Post date:** [January 23, 2016, 9:57am UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/3 "2016-01-23T09:57:03Z")
Yes, but I do not have “before” and “after” texts to feed to diff later. Only a list of files annotated with flags about how they were changed. Basically, if self.\_diff is True I want to print something to the Ansible output below [changed]. Is that possible? cf: [http://andreafrancia.it/2010/03/understanding-the-output-of-rsync-itemize-changes.html](http://andreafrancia.it/2010/03/understanding-the-output-of-rsync-itemize-changes.html) ---
**Author:** ![Brian\_Coca](https://avatars.discourse-cdn.com/v4/letter/b/6de8d8/32.png) [@Brian\_Coca](https://forum.ansible.com/u/Brian_Coca)\ **Post date:** [January 23, 2016, 4:06pm UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/4 "2016-01-23T16:06:03Z")
not yet, but we can always add a new key (unified?) and display that directly when present ---
**Author:** ![Tobias\_Wolf](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tobias\_Wolf](https://forum.ansible.com/u/Tobias_Wolf)\ **Post date:** [January 25, 2016, 12:20pm UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/5 "2016-01-25T12:20:58Z")
Ok, I issued two pull requests. One that introduces the diff[‘custom’] key for lack of a more descriptive name[1]. The other[2] adds this field to the synchronize module, which would close an issue[3] on the tracker. [1] [https://github.com/ansible/ansible/pull/14105](https://github.com/ansible/ansible/pull/14105) [2] [https://github.com/ansible/ansible-modules-core/pull/2870](https://github.com/ansible/ansible-modules-core/pull/2870) [3] [https://github.com/ansible/ansible/issues/11262](https://github.com/ansible/ansible/issues/11262) Would appreciate feedback, or a merge. ---
**Author:** ![Rene\_Moser](https://avatars.discourse-cdn.com/v4/letter/r/7bcc69/32.png) [@Rene\_Moser](https://forum.ansible.com/u/Rene_Moser)\ **Post date:** [January 26, 2016, 7:21am UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/6 "2016-01-26T07:21:27Z")
Hi Brian > In current devel (future 2.1.0) modules can check module.\_diff boolean > property to figure out if they are in diff mode or not, returning a > dictionary with the differences keyed to 'diff' will automatically be > used by the default callbacks to display it. This sounds interesting, didn't look in detail yet, but in my use cases (cloudstack modules). I compare [1] values and keys of 2 dicts.I thought about how I would return the diff in this case. I came to the conclusion that I would return a dict with all key/values which are different. What do you think? Regards René [1] [https://github.com/ansible/ansible/blob/devel/lib/ansible/module\_utils/cloudstack.py#L133](https://github.com/ansible/ansible/blob/devel/lib/ansible/module_utils/cloudstack.py#L133) ---
**Author:** ![Brian\_Coca](https://avatars.discourse-cdn.com/v4/letter/b/6de8d8/32.png) [@Brian\_Coca](https://forum.ansible.com/u/Brian_Coca)\ **Post date:** [January 26, 2016, 2:59pm UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/7 "2016-01-26T14:59:24Z")
check the file module in devel, i was thinking along those lines (though might need new entry to not conflict with the files themselves) ---
**Author:** ![Tobias\_Wolf](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tobias\_Wolf](https://forum.ansible.com/u/Tobias_Wolf)\ **Post date:** [February 2, 2016, 2:11pm UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/8 "2016-02-02T14:11:26Z")
In addition to the already merged diff support for synchronize I filed pull requests for these two - apt: [https://github.com/ansible/ansible-modules-core/pull/2944](https://github.com/ansible/ansible-modules-core/pull/2944) - lineinfile.py: [https://github.com/ansible/ansible-modules-core/pull/2896](https://github.com/ansible/ansible-modules-core/pull/2896) Would appreciate feedback, or a merge. Both of those close long existing feature requests. –Tobias ---
**Author:** ![Brian\_Coca](https://avatars.discourse-cdn.com/v4/letter/b/6de8d8/32.png) [@Brian\_Coca](https://forum.ansible.com/u/Brian_Coca)\ **Post date:** [February 2, 2016, 2:33pm UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/9 "2016-02-02T14:33:11Z")
both are in my queue for testing, gave apt a quick glance and it looks good ---
**Author:** ![Mike\_Biancaniello](https://avatars.discourse-cdn.com/v4/letter/m/dec6dc/32.png) [@Mike\_Biancaniello](https://forum.ansible.com/u/Mike_Biancaniello)\ **Post date:** [February 2, 2016, 4:13pm UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/10 "2016-02-02T16:13:15Z")
I was actually going to do something along these lines (I work with Juniper routers that construct their own diffs and since the files can be quite large, sending before+after for a single line change is kind of silly). Then, I noticed that the devel (future 2.1.0) callback looks for diff[‘prepared’]. I ended up modifying my Juniper router module to add the router-created diff to diff[‘prepared’] in the response and ansible handles it beautifully. ---
**Author:** ![Mike\_Biancaniello](https://avatars.discourse-cdn.com/v4/letter/m/dec6dc/32.png) [@Mike\_Biancaniello](https://forum.ansible.com/u/Mike_Biancaniello)\ **Post date:** [February 2, 2016, 4:14pm UTC](https://forum.ansible.com/t/how-do-i-get-a-module-to-work-with-diff/20318/11 "2016-02-02T16:14:32Z")
See: [https://github.com/ansible/ansible/blob/devel/lib/ansible/plugins/callback/\_\_init\_\_.py#L134](https://github.com/ansible/ansible/blob/devel/lib/ansible/plugins/callback/ __init__.py#L134)