No error when removing field from data structure without migration

[lippling]

Hi,

I have the following code:

data File = File {
    fileName     :: String
  , filePath     :: FilePath
  , fileContents :: ByteString
}
$(deriveSafeCopy 0 'base ''File)

data Database = Database [File]
$(deriveSafeCopy 0 'base ''Database)

addFile :: File -> Update Database ()
addFile file = do
    Database files <- get
    put $ Database (file:files)

viewFiles :: Int -> Query Database [File]
viewFiles limit = do
    Database files <- ask
    return $ take limit files

$(makeAcidic ''Database ['addFile, 'viewFiles]) 

I did some tests and in one test I removed the fileName field. Then I ran a ViewFiles 10 query and no error showed up, but the resulting data was incorrect.

For example:
I inserted File "a" "b" "c" and after removing the field I got Field "a" "\NUL" back.

It was also possible to add new Files to the state. The new Files were ok when retrieved by a query. (A migration solved the problem too, of course).

Is this behavior intentional or a bug? I would expect an error, because the structure doesn't match the persisted structure.

[stepcut]

This is a limitation of the way SafeCopy is currently implemented. It is expected behavior -- but an error would be better. The short answer is "don't do that". The long answer is that it would be nice (for a variety of reasons) if acid-state/safecopy could produce a schema for the .log files.