CC @ianlancetaylor

Embedded directories do not implement Seek. (This bit me yesterday.)

Ah, I see. So I want a guarantee that (*embed.FS).Open returns a fs.File that implements io.Seeker when the returned value is a file, not a directory.

Yep. Or we could make directories seekers too, I guess.

I think it would be fine to document that the result of embed.FS.Open, when opening a file that is not a directory, will implement io.Seeker.

This doesn't have to be a proposal, so taking it out of the proposal process.

Yep. Or we could make directories seekers too, I guess.

This sounds better to me, as *os.File has Seek even for directories. Always returning an error at openDir.Seek should be fine.

I think it would be fine to document that the result of embed.FS.Open, when opening a file that is not a directory, will implement io.Seeker.

Hmm, always having Seek sounds less confusing. What do you think?

While it might be true currently, wouldn’t adopting this make it impossible/much-more-difficult for the compiler to change how embedded files are stored? For instance to automatically compress them. I seem to recall being able to decide that kind of thing at a later time was part of the original proposal or discussion.

I suppose I don't see a reason to support Seek for embedded directories. And we don't support it today.

Since we already support Seek for embedded files, it's going to be pretty hard to change that. We can still compress the embedded data, we'll just have to decompress the entire file if it is opened.

Change https://golang.org/cl/313352 mentions this issue: embed: guarantee the returned file of FS.Open implements io.Seeker