pattern matching in hostfs doesn't match fatfs (f_findfirst bug)

[stevesims]

When MOS makes a call to the faffs's f_findfirst function, passing in a pattern of "" (i.e. an empty string) and providing a path to a valid directory, the expected behaviour from fatfs is to return FR_OK, but leave the file info object with an empty filename, as there was not actually a file to match against

The emulator however will return the first file it finds inside the given path. It behaves instead as if a pattern of * had been set, rather than an empty string.

It should be noted that the emulator does not implement f_findfirst itself - instead it patches over f_opendir and f_readdir, the building blocks that f_findfirst makes use of. inside f_findfirst fatfs first sets a pat value on the dir object passed into the function to the pattern being matched for the find call. it then calls f_findnext which in turn will call f_readdir to read the first matching directory entry.

It should be noted that file pattern matching does work inside the emulator. calling f_findfirst with a pattern string that is anything besides an empty string will work as expected. (At this time I cannot see how it accomplishes that.)

A simple work-around for this limitation (discovered whilst writing this ticket 😁 ) is to set the pattern to .. ideally the emulator should use that work-around itself, as when MOS eventually exposes the use of f_findfirst to other applications they may run into this same issue