Report failed action names on dispatch failure

[ajay]

When dotbot fails, the error message currently only says:

Some tasks were not executed successfully

This provides no indication of which actions failed, forcing the user to scroll back through the log to identify the problem. This is especially painful with long-running configs that have many actions (package installs, linking, shell commands, etc.), or when running with verbose flags.

This PR adds tracking of failed action names and includes them in the error message.

Before:

[ERROR] Some tasks were not executed successfully

After:

[ERROR] Some tasks were not executed successfully: shell-dnf, link

Backwards Compatibility

The dispatch() -> bool signature is unchanged. The new get_failed_actions() method is additive. Existing third-party plugins that call dispatcher.dispatch(tasks) will continue to work without modification.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.29%. Comparing base (00f319c) to head (433f61e).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #397      +/-   ##
==========================================
+ Coverage   89.70%   90.29%   +0.58%     
==========================================
  Files          21       21              
  Lines         826      835       +9     
==========================================
+ Hits          741      754      +13     
+ Misses         85       81       -4     

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[ajay]

@anishathalye Bump, does this change look reasonable to you?

[anishathalye]

Sorry, been a bit backlogged, as I often am 😅

Will try to take a look in the next couple days.

[anishathalye]

Overall seems like a fine idea. One detail is that Dotbot configuration is a list of "tasks", where each task can have multiple "actions". This is mostly historical, I think these days most people use one action per task.

What should the right behavior be when there are potentially multiple actions per task, and the same action can appear multiple times across tasks (e.g., there may be multiple shells)? Should we show the unique set of actions that failed? Show failed actions with multiplicity?

Also, to avoid mixing up tasks and actions in the error message, we could make the error message something like:

Some tasks were not executed successfully (failed actions: shell-dnf, link)

Thoughts?

[anishathalye]

This may also be messy enough that it's not worth it. Do users have configs that are so big that the output from Dotbot is hard to parse and a summary of failed actions would be helpful? Is your config large enough for this / what motivated this change?