Prevent improper files (like /dev/random) from being used as file arguments

[TiredTumblrina]

As per the suggestions in #10726 this pull request changes the argument parsing to only add a PathBuf to args.files if it is either a file or a symlink. This has been tested on the scenarios provided in the issue and simply opens an empty buffer as if no argument was provided in those cases. (instead of freezing)

[pascalkuthe]

I don't think the arg parsing is the right place to do this. We should fundamentally disallow opening non-files so it's consistent with :open/:vsplit and any other way a user would open a path

[TiredTumblrina]

That is a good point, I'll see if I can get this to work in a more interoperable way and will amend the PR

[TiredTumblrina]

By making changes to the Document::open method I have the :open command working as expected, however when I revert the prior changes to argument parsing the application errors out ungracefully:

> hx /dev/random
Error: unable to create new application

Caused by:
    0: open '/dev/random'
    1: Path argument /dev/random should lead is not a regular file or a symlink.

In this case, maybe it would be better to keep both checks so that the application does not crash when it gets an invalid input?

[kirawi]

You probably need to handle that error and just create an empty scratch buffer if the file can't open.

[TiredTumblrina]

done, thank you all for the suggestions and advice!

[the-mikedavis]

Overall this looks good to me but it seems like a nice opportunity for a small refactor since we start to care about what error type is returned by Editor::open. Since we care about "which error" happened let's switch away from returning an anyhow::Error and introduce a custom error type. We can write a pretty small one that doesn't need too many changes to the code that uses it with thiserror (which we already depend on in other crates):

#[derive(Debug, Error)]
pub enum DocumentOpenError {
    #[error("path must be a regular file, symlink or directory")]
    IrregularFile,
    #[error(transparent)]
    IoError(#[from] io::Error),
}

Document::open and all of the functions called within actually only return std::io::Errors at the moment so this refactor is mostly about changing the return types of those functions from Result<Whatever, anyhow::Error> to Result<Whatever, io::Error>. Then when we see that the file isn't a regular file in Document::open we can return Err(DocumentOpenError::IrregularFile) and we can match on that error exactly in application.rs.

[TiredTumblrina]

Thanks for the review! I've taken a stab at the refactoring, although let me know if more changes are needed, as I'm not too sure if some of the changes I made are ideal (especially those in application.rs).

[the-mikedavis]

Looking good! I just have some small nits