Add :quit repl command #719
Conversation
Gabriella439
left a comment
There was a problem hiding this comment.
@kedashoe: Your solution is actually just fine. The Interrupt exception is how repline expects to signal the end of the REPL eval loop. Just one minor comment
dhall/src/Dhall/Repl.hs
Outdated
| cmdQuit :: ( MonadIO m, MonadState Env m ) => [String] -> m () | ||
| cmdQuit _ = do | ||
| liftIO (putStrLn "Goodbye.") | ||
| throw Interrupt |
There was a problem hiding this comment.
You usually want to prefer throwIO instead of throw since throw can accidentally be triggered by evaluation whereas throwIO is evaluation-safe. Or in other words:
throw x `seq` () = throw x
throwIO x `seq` () = ()| throw Interrupt | |
| liftIO (throwIO Interrupt) |
There was a problem hiding this comment.
ah so technically it is possible it could throw without putStrLning? Updated.
There was a problem hiding this comment.
Yeah! The repline loop has logic that checks if the last command was non-empty when an Interrupt was thrown. If the command is empty then it says Goodbye. and if it was non-empty then it says nothing. This is why you had to insert an explicit Goodbye. to match the behavior because :quit was a non-empty command.
|
Thank you for contributing this! 🙂 |
For #707
Not sure what the "best" way to quit is,
throw Interruptseems a bit odd to me but I couldn't figure out a better way..