FSWriteStream>>nextPut: does not truncate a file in memory

[MariusDoe]

When using an FSMemoryStore, after closing a write stream that only called nextPut:, the file is not properly truncated. nextPutAll: does not have this behavior.

| fs ref |
fs := FileSystem memory.
ref := fs / 'test'.
ref writeStreamDo: [:s | s nextPutAll: 'abc'].
ref contents. "'abc'"
ref writeStreamDo: [:s | s nextPutAll: 'xy'].
ref contents. "'xy'"
ref writeStreamDo: [:s | s nextPut: $!].
ref contents. "'!y'"

Some investigation:

• FSWriteStream>>basicNextPut: calls at:put: on the FSMemoryHandle
• at:put: is overridden on FSMemoryHandle, to (among other things) do size := size max: index (keeping at least the original size)
• normally (in FSHandle>>at:put: and with basicNextPutAll:), at:write:startingAt:count: is called, which, on FSMemoryHandle, sets size to the index of the byte that was written last (correctly truncating the file)

I'm not sure whether basicNextPut: is at fault for calling at:put: instead of at:write:startingAt:count: or whether at:put: should instead set the size to the index - maybe at:put: is sometimes used to set bytes in the middle of a file, without wanting a truncation?