remove the if ...

no, it's there on purpose...

the default implementation of extra_options in EasyBlock must still return a list (of tuples) for now, until we switch to making it return a dict in EasyBuild v2.0

the list will be empty by default though, so I've added the check here to only complain in case the list is non-empty...

then you are not deprecating anything yet. the new format should work, any old behaviour should be converted in new style.

this makes no sense. either deprecate the oldstyle or not.

We can't get rid of the old-style config file yet, since it still handles old-style configuring... The deprecation of the old-style variables etc. is handled in different places.

Without the if, using --deprecated triggers a deprecation error straight away, since easybuild_config.py is still there (and must be).

We can trigger a deprecation (error) if a non-default old-style config file was specified via -C.

same remark as above: then you are not deprecating anything. the actual move to 2.0 should be no more then removing code blocks that convert oldstyle in new style.

I could reimplement what the old-style default config file easybuild_config.py does in config.py, but that would be wasted effort since we actually want to get rid of it

the deprecation of what is being defined via easybuild_config.py is handled in other places, in code blocks that can simply be dropped once we clean things up (EasyBuild v2.1?)

note that this whole block will disappear too (anything under the if SUPPORT_OLDSTYLE), so with EasyBuild v2.1 we will be able to just delete all of this, no need to convert code at all...

why the elif? also for HybridListDict .items() should work? make the above

if isinstance(opts, (dict, HybridListDict)):

true that, will fix

well, I do have a reason actually... keeping this separate makes it easy to remove this again in a future version, instead of having to refactor code to flesh out the HybridListDict...