ErrShortBuffer is only used by ReadAtLeast.

Also, you shouldn’t need ErrShortBuffer with Reader. It’s legal to fail if len(p) is less than some desired buffer size, but non-standard as Readers conventionally return partial data instead of no data.

The problem with partial reads with small buffer is that they aren't actually possible with the current io.ReadAll() implementation.

https://play.golang.org/p/9e5bcYIb_1n

For a first read, partialReader has a buffer of 512 bytes. If it returns 256 then on the next read io.ReadAll() gives a buffer of only 256 bytes. If it wasn't enough on a first read then it won't get any bigger on the second one.

There's just no way for a downstream Reader to signal to upstream that this buffer isn't big enough for the read.

There's just no way for a downstream Reader to signal to upstream that this buffer isn't big enough for the read.

The io.Reader API does not provide any mechanism for that. The expectation is that any type that implements io.Reader and can only read entire chunks at a time will do its own buffering. There is no other way to honor the io.Reader interface.

As @ericlagergren says, an implementation of io.Reader should never return io.ErrShortBuffer.

I'm going to close this issue because I don't think there is anything to change here. Please comment if you disagree.