raise error for patches without .patch extension and no destination given (WIP)

[smoors]

fixes #3688

[boegelbot]

@smoors: Tests failed in GitHub Actions, see https://github.com/easybuilders/easybuild-framework/actions/runs/930954127
Output from first failing test suite run:

ERROR: test_exts_list (test.framework.easyconfig.EasyConfigTest)
Test handling of list of extensions.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/runner/6d4aa4fdc0b5a03ef8615fca018a066aacb6668e/lib/python2.7/site-packages/test/framework/easyconfig.py", line 477, in test_exts_list
    exts_sources = eb.fetch_extension_sources()
  File "/tmp/runner/6d4aa4fdc0b5a03ef8615fca018a066aacb6668e/lib/python2.7/site-packages/easybuild/framework/easyblock.py", line 626, in fetch_extension_sources
    ext_patches = self.fetch_patches(patch_specs=ext_options.get('patches', []), extension=True)
  File "/tmp/runner/6d4aa4fdc0b5a03ef8615fca018a066aacb6668e/lib/python2.7/site-packages/easybuild/framework/easyblock.py", line 471, in fetch_patches
    "For file to copy, use tuple(filename, destination)", patch_spec)
EasyBuildError: "No '.patch' suffix in file toy-0.0.eb implies file to copy, but no destination path given. For file to copy, use tuple(filename, destination)"

----------------------------------------------------------------------
Ran 782 tests in 1059.240s

FAILED (errors=1)
ERROR: Not all tests were successful.

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[boegel]

@smoors Isn't the copy location implicitly the current directory then, in the current implementation? Cfr. the failing test...

So, rather than making this a backwards-incompatible change, maybe we should deprecate it instead, and make it an error only in EasyBuild 5.0?

Can you also check whether any of the easyconfigs in the central repository will need to be updated?

[smoors]

@boegel no, the failing test stops at fetch_extension_sources(), so it's not actually doing anything with the patch beyond fetching and checking.

In the current implementation, implicit copy is currently only done for patches without .patch suffix that have a path associated with them, as in tuple(filename, destination). In all other cases it is treated as a normal patch.

I also checked the central EB repository, and the few 'patches' that don't have a .patch suffix all have a path, so there's nothing to update there.

It's only backward incompatible for the rare cases where users deviate from the documentation that says patches should have .patch suffix: https://caylo-easybuild.readthedocs.io/en/latest/Writing_easyconfig_files.html#source-files-and-patches

For me the current behavior is problematic, especially for new users, because in some cases it's ok to have a patch without .patch suffix, while in other cases it just copies the patch without actually patching anything.

But if you prefer to deprecate it first, that's ok with me. Do you still prefer that?

[smoors]

superseded by #3920