What's the best way of doing a dependency check in a modular input?

[gf13579]

I'm using the AddOn Builder 2 to build a modular input based on a python script that wraps around an external command.

I want to do a dependency check - ideally as part of the UI used by the user to set the app up, rather than at runtime in collect_events or validate_input.

I want to check that a given binary is present on the system and advise the user to install it - if not already present. Any suggestions?

Bonus question: does validate_input actually get called when using the AddOn Builder to test a python script? I'm raising ValueError(...) but the AoB still successfully invokes collect_events regardless.

[chli_splunk · Accepted solution]

You are right you can use validate_input() method. Just raise an exception like this:
raise Exception("error message")

Then the error will be shown in UI.

[gf13579]

I figured out that validate_input gets called when the user creates/updates an input (makes sense now) but there doesn't seem to be anyway to pass a useful message back to the user at that point - any tips?