CLI: Fix exception for verdi plugin list

[sphuber]

Fixes #6557

In e952d77 a bug in verdi plugin list was fixed where the conditional to check whether the plugin was a process class would always raise an AttributeError if the plugin was not a Process or a proces function. As a result, the code would never get to the else-clause.

The else-clause contained itself another bug, which was now revealed by the fixing of the bug in the conditional. The else-clause would call the get_description classmethod of the plugin, but no classes in AiiDA that are pluginnable even define such a class method. Probably, the original author confused it with the instance method get_description but the verdi plugin list command just deals with the class.

The get_description call is replaced with just getting __doc__ which returns the docstring of the class/function, or None if it is not defined. In the latter case, a default message is displayed saying that no description is available.

Since the else-clause code was never reached before the recent fix and the get_description method was never supported officially by AiiDA's pluginnable interfaces, it is fine to just change this behavior.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.83%. Comparing base (ef60b66) to head (2bea022).
Report is 133 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6560      +/-   ##
==========================================
+ Coverage   77.51%   77.83%   +0.33%     
==========================================
  Files         560      566       +6     
  Lines       41444    41983     +539     
==========================================
+ Hits        32120    32675     +555     
+ Misses       9324     9308      -16     

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[khsrali]

Thanks, @sphuber.
Changes make sense; the only thing is backward compatibility for plugins that have their description stored in 'get_description()' as a classmethod.

But since this is only a description, I think it's fine.

[sphuber]

Thanks, @sphuber. Changes make sense; the only thing is backward compatibility for plugins that have their description stored in 'get_description()' as a classmethod.

Which plugins would have this though? This has never been part of any plugin API. There are no classes in AiiDA that have the get_description class method as part of their interface. It was just a mistake in verdi plugin list that wasn't even ever hit because of the other bug.

[khsrali]

Which plugins would have this though? This has never been part of any plugin API. There are no classes in AiiDA that have the get_description class method as part of their interface. It was just a mistake in verdi plugin list that wasn't even ever hit because of the other bug.

aiida-firecrest was doing it that way, simply because of the way plugin_list() was written we thought that's the way.

Of course this would be an easy change for us.
Just saying that there might be other plugins out there that thought the same.

[sphuber]

aiida-firecrest was doing it that way, simply because of the way plugin_list() was written we thought that's the way.

Ah I see, well in that case I think it is fine as you say. Thanks for the review