don't assume File.mkdir_p succeeds when writing metadata.

[kivikakk]

This is a minor change which makes working with Nix a little bit easier.

write_metadata/2 passes a failed file write to its caller, __using__/2, which logs it as a warning. This is great, but on Nix the File.mkdir_p/1 fails before we get there, and currently this causes the whole process to abort.

This PR just forwards any error from File.mkdir_p/1 to the caller instead of raising a MatchError.

[philss]

@kivikakk thank you for the PR! This makes sense to me. Can you please run mix format, so it passes the linter?

Also, there is another way to write the same thing you did with the with macro:

with :ok <- File.mkdir_p(dir) do
  File.write(metadata_file, inspect(metadata, limit: :infinity, pretty: true))
end

This means that if the match is unsuccessful, the code will return whatever the result of the expression is.

[kivikakk]

@kivikakk thank you for the PR! This makes sense to me. Can you please run mix format, so it passes the linter?

Also, there is another way to write the same thing you did with the with macro:

Thank you! I've used that (and run mix format).

[kivikakk]

Ta! :)