Handle Unknown errors in Erlang

[felixakiragreen]

Issue Described Here

How this happened:

• I encountered an unmatched clause {error,ehostdown} when trying to write .append() to a file mounted via smb.

What I did:

• Added a case for the POSIX error to is_posix_error in simplifile_erl.erl.
• @lpil noticed that in JavaScript unknown errors are converted to Unknown, but on Erlang it crashes.
• Added an unknown error case to posix_result, which converts the reason into a string.
• Added a test to ensure that any unknown errors properly return the Unknown type.

Questions:

• I discovered a number of lists of POSIX errors that had many more errors on them. This one by Apple seems to be one of the most comprehensive. If you want I can add support for the rest of them.
• The first test I wrote worked in Erlang, Node, and Bun, but not Deno. So in order to force an unknown error uniformly across all runtimes, I created a shim that let me pass in a bad argument. I hope this is acceptable, if you know another way please let me know.

[lpil]

This is a breaking change. Would it be better to use Unknown?

[lpil]

I think atom_to_binary would be better used here.

Would it also make sense to uppercase the string? To match how it is written in POSIX (and also also the JavaScript target)

[lpil]

This module could be removed and the @external reference ./simplifile_js.mjs directly.

[bcpeinhardt]

@felixakiragreen thank you for fixing this!

I think the main issue here is the crash/difference in error behavior. I think first, a PR fixing the erlang ffi to make use of the Unknown error variant to prevent the crash would be good that could be released as a patch version.

If we decide to change the list of recognized errors, we can do that in a follow up PR.

[bcpeinhardt]

The atom_to_binary function defaults to utf8, so it should be fine to pass the resulting binary to string:uppercase

[bcpeinhardt]

This was a docs update that doesn't affect the version number, so I think it shouldn't be in the changelog.

[bcpeinhardt]

closes #54

[felixakiragreen]

Thank you so much! 🙏