Platform independent path comparison

[suvayu]

The datapackage spec requires all paths in the package metadata to be POSIX paths, however the implementation doesn't enforce this in a platform independent manner, so some functions when run on Window can generate path strings like "path_to\\data.csv". This poses two problems:

1. corrupt/non-conformant package metadata maybe written
2. path comparisons may fail on some OS combinationss (when package creation and the path comparison are not happening on the same OS).

Two separate resolutions are required:

• ensure paths in the metadata are POSIX paths (implemented in sark.dpkg._ensure_posix)
• a uniform interface to do path comparisons
  1. if the files are same, aka, Path(..).samefile(..)
  2. if two relative paths are same (may not point to the same file, as depends on base path)

[olejandro]

@suvayu, it seems that ensuring POSIX causes dpkg.read_pkg() to fail on datapackages with inline data (and therefore no path specified). Here is an example: https://github.com/MaREI-EPMG/ireland-carbon-budget-scenarios-2021/security

[suvayu]

I'm not surprised since I never tested with inline data :(. Do you get KeyError of some kind?

I'm employed elsewhere now, so I need to find some free time outside of work to fix this. Probably not a big fix though.

[olejandro]

Thanks a lot! yes, it is complaining that path is missing.
I've just submitted a pull request removing a windows specific check for posix. It seems no longer needed (?)

[suvayu]

Hi @olejandro I fixed the issue with #26, please have a look if it works for you.