Additional CHANGE_SUCCESS_CMD Functionality

[alex-courtis]

#162 adds CHANGE_SUCCESS_CMD as a success hook. Additional information coould be built on this.

Issue to discuss these @matthewwardrop

Possibilites include:

• human readable change notification #65 add ON_CHANGE_CMD to run a shell command in handle_success #162 (comment)
• failure hook
• machine readable yaml before and after files similar to the human readable ones
• config reload hook

[matthewwardrop]

Hi @alex-courtis ; apologies for the delay (as usual life expects a lot from me!).

What kind of feedback would you like here? I really like the idea of state-change hooks, but it does seem like a missed opportunity to think more about both additional hooks (like failures) and multiple hooks for the same state change. I suspect we could run multiple commands in the existing implementation by stacking sh-commands... though I cannot remember (and don't have time to look into the code as I type this to check) whether multi-line strings are supported by the config parser [call me lazy, but I don't want to have to create another external script file to act as the hook].

I do also like the idea of a "last" state, but I'm not sure in practice how much value it would add. I don't think I would use it personally. I'm also not sure what I would do with a config reload hook (as distinct from the mode-changes effected by reloading the config), but perhaps there are good examples?

[alex-courtis]

Many thanks for your thoughts!

I suspect we could run multiple commands in the existing implementation by stacking sh-commands... though I cannot remember (and don't have time to look into the code as I type this to check) whether multi-line strings are supported by the config parser [call me lazy, but I don't want to have to create another external script file to act as the hook].

That is achievable. YAML does support multiline. Providing the command is expressed as a single shell executable e.g. notify-send foo ; notify-send bar it should function.

Script files in this sort of context are divisive. The user could use either, however a script could be encouraged as multiple commands could be difficult for the novice shell scripter.

I do also like the idea of a "last" state, but I'm not sure in practice how much value it would add.

Yes, I'm also not quite sure of a use case beyond some script action that depends on the delta.

I'm also not sure what I would do with a config reload hook

Unless this is completely trivial, YAGNI.

[alex-courtis]

Actually, multiline came out nicely:

https://github.com/alex-courtis/way-displays/wiki/Configuration#change_success_cmd

[matthewwardrop]

Love it!

[alex-courtis]

Work in progress: #168

Human readable change message is written to a file for notify-send to post.

It might be time to remove all but the changed attribute from the "from:".