add support for post install commands for Python extensions

[smoors]

post install commands can be done with a hack if using python setup.py install:

'installopts': ' && some_post_install_stuff',

with pip however, this hack is not possible.

this PR adds support for post install commands for each individual extension, so one can use it in the same way as the usual postinstallcmds:

'ext_postinstallcmds': [list of commands]',

[ocaisa]

Since postinstallcmds is already in framework, I think it would be better to name this option to something like ext_postinstallcmds so that it'll turn up when searching the repo

[smoors]

@ocaisa thanks for the suggestions.
I've changed it to ext_postinstallcmds and made the code similar to how postinstallcmds was implemented, with added type checks.
I've also changed the default value to None instead of [] as this is also the case for postinstallcmds.

[ocaisa]

Code LGTM, have you got an easyconfig that uses it?

[smoors]

@ocaisa see easybuilders/easybuild-easyconfigs#12559

[ocaisa]

Tested with easybuilders/easybuild-easyconfigs#12559 and looks good, relevant output excerpt below, no impact on other extensions and does what it says on the tin:

== installing extension about 5.2 (5/7)...
  >> defining build environment for foss/2020b toolchain
  >> running command:
	[started at: 2021-04-10 08:02:04]
	[working dir: /users/ocaisa/.local/easybuild/build/DROP/1.0.3/foss-2020b-R-4.0.3/about]
	[output logged in /tmp/eb-7p6f46c9/easybuild-run_cmd-8lijbxou.log]
	tar xzf /shared/maintainers/sources/d/DROP/extensions/about-5.2.tar.gz
  >> command completed: exit 0, ran in < 1s
== 	configuring...
== 	building...
== 	testing...
== 	installing...
  >> running command:
	[started at: 2021-04-10 08:02:05]
	[working dir: /users/ocaisa/.local/easybuild/build/DROP/1.0.3/foss-2020b-R-4.0.3/about/about-5.2]
	[output logged in /tmp/eb-7p6f46c9/easybuild-run_cmd-jqxzxvve.log]
	pip install --prefix=/users/ocaisa/.local/easybuild/software/DROP/1.0.3-foss-2020b-R-4.0.3  --no-deps  --ignore-installed  --no-build-isolation  .
  >> command completed: exit 0, ran in 00h00m01s
== installing extension pandoc 1.0.2 (6/7)...
  >> defining build environment for foss/2020b toolchain
  >> running command:
	[started at: 2021-04-10 08:02:07]
	[working dir: /users/ocaisa/.local/easybuild/build/DROP/1.0.3/foss-2020b-R-4.0.3/pandoc]
	[output logged in /tmp/eb-7p6f46c9/easybuild-run_cmd-9tvs15xk.log]
	tar xzf /shared/maintainers/sources/d/DROP/extensions/v1.0.2.tar.gz
  >> command completed: exit 0, ran in < 1s
== 	configuring...
== 	building...
== 	testing...
== 	installing...
  >> running command:
	[started at: 2021-04-10 08:02:07]
	[working dir: /users/ocaisa/.local/easybuild/build/DROP/1.0.3/foss-2020b-R-4.0.3/pandoc/pandoc-1.0.2]
	[output logged in /tmp/eb-7p6f46c9/easybuild-run_cmd-u7trm40w.log]
	pip install --prefix=/users/ocaisa/.local/easybuild/software/DROP/1.0.3-foss-2020b-R-4.0.3  --no-deps  --ignore-installed  --no-build-isolation  .  && cp -a pandoc/definitions /users/ocaisa/.local/easybuild/software/DROP/1.0.3-foss-2020b-R-4.0.3/lib/python3.8/site-packages/pandoc/
  >> command completed: exit 0, ran in 00h00m01s

[boegel]

Hmm, I wonder if it wouldn't have been better to use the existing postinstallcmds instead...

You can already specify postinstallcmds for a specific extension (just like any other common easyconfig parameter), but doing so won't have any effect, unless a change like this is made in easyblocks that are used to install extensions.

So, how about just renaming to ext_postinstallcmds to postinstallcmds here after all (and removing the support for picking up ext_postinstallcmds, while this is still only in develop?

cc @smoors, @ocaisa

[smoors]

@boegel that would indeed be better.
I went for another parameter to avoid the clash with the global postinstallcmds, but it's easy to fix this, by adding this line to the __init__ function in extensionblock.py (similar to the start_dir parameter):

self.cfg['postinstallcmds'] = self.ext.get('options', {}).get('postinstallcmds', None)

because of the clash I assumed this was intended, but now I understand it was just not yet implemented.
I can make a PR for this if that's the way to go.