It breaks. Which is weird because you can create a string which isn't valid UTF-8 (eg "\xbd\xb2\x3d\xbc\x20\xe2\x8c\x98") and print it out with no trouble; you just can't pass it to e.g. `os.Create` or `os.Open`.
(Bash and a variety of other utils will also complain about it being valid UTF-8; neovim won't save a file under that name; etc.)
$ cat main.go
package main
import (
"log"
"os"
)
func main() {
f, err := os.Create("\xbd\xb2\x3d\xbc\x20\xe2\x8c\x98")
if err != nil {
log.Fatalf("create: %v", err)
}
_ = f
}
$ go run .
$ ls -1
''$'\275\262''='$'\274'' ⌘'
go.mod
main.goYes, that was my assumption when bash et al also had problems with it.
If you stuff random binary data into a string, Go just steams along, as described in this post.
Over the decades I have lost data to tools skipping non-UTF-8 filenames. I should not be blamed for having files that were named before UTF-8 existed.
Windows doing something similar wouldn't surprise me at all. I believe NTFS internally stores filenames as UTF-16, so enforcing UTF-8 at the API boundary sounds likely.