tidal "safe mode" for use with (web) collaborative/shared editors

[jwaldmann]

In collaborative live coding, there's always the problem that (by malice or by accident) some input can extract information from the system that runs tidal, or worse. Think of sending :! echo wat to ghci, and work from there ...

See discussion at https://github.com/munshkr/flok/issues/2 They want to have a language-agnostic solution, since their editor is.

I can imagine something that works just for tidal - since this is Haskell, and we have strong typing, we can simply forbid IO. Other languages can't.

I have experience with a similiar problem: automatically grading student (Haskell) programming exercises. My solution is that I force their code to match some blueprint (they can only fill in holes in specific places - for tidal, I imagine this would be _ in d1 $ _) and the compiler will check that the code is properly typed (in our case, the argument must be :: Pattern ControlMap).

I know this would exclude some tidal coding tricks (do { let foo = ... ; d1 $ .. ; d2 $ .. }) since this does not match the pattern, and you could still DOS the server (d1 $ let x = x in x) but so be it.

Summary: I can imagine an executable that

• connects to SuperDirt on startup
• accepts text blocks of the shape "dX $ ..." on stdin
• evaluates the argument with https://hackage.haskell.org/package/mueval , applies "dX" to the result
• prints something useful to stdout and stderr

This would also solve the problem of "where does tidal find its boot file", because this will be baked into the executable. - Well, it'll be traded for the problem that mueval needs to find the tidal modules for type checking and evaluation.

[jwaldmann]

Is this "minitidal" (#452)? Not really, my plan is to use mueval/hint. You mention this option in the linked issue.

[yaxu]

Hi @jwaldmann

A drop-in replacement for ghci would be amazing. If we could make it redistributable without the whole of ghc, that would be a game changer.. However, this is unfortunately difficult. https://github.com/haskell-hint/hint/issues/80

There has been some work on this sort of thing in the past.

I once made this: https://github.com/yaxu/tidal-websocket

In the 'data' folder is a html-based editor (using codemirror) that sent code to the websocket.

It would need some fixes up to work with newer tidal..

There was some discussion towards formalising the protocol here: https://github.com/tidalcycles/Tidal/issues/159

https://twitter.com/tidalbot/ is no longer working, but it used to use hint too.

I also made a django-based website in the past that rendered patterns as well: https://github.com/yaxu/patternlib

That bitrotted too..

[jwaldmann]

Hi.

I just made this https://github.com/jwaldmann/safe-tidal-cli (very naive) and I am trying to declare it as a repl for flok https://github.com/munshkr/flok/issues/64

The safe-tidal-cli is working locally (I send text to stdin, it sends commands to SuperDirt as it should). I am actually surprised that it found the Tidal library! But, ghci also finds it, since I did cabal install --lib tidal.

[EDIT] connection to flok is working now.

Of course, this repl needs to be made more robust, it needs a better input parser, better error reporting and so on.

[EDIT] and I think it will totally not solve the "make tidal distribution/deploy easier" problem: Hint loads Sound.Tidal.Context, so this needs to be installed first.

[jwaldmann]

I now have a version that solves the conflict

• want to provide usual d1 $ ... but also do { this ; that }
• but still don't want arbitrary user-defined IO

I am wrapping the Tidal functions that produce IO, don't expose the constructor, and the wrapper is a monad as well, see https://github.com/jwaldmann/safe-tidal-cli/blob/master/src/Sound/Tidal/Safe/Context.hs

This does not allow code blocks let foo = bar because we can't change the state of the ghci session.

[kuhy]

Hi.

I just made this https://github.com/jwaldmann/safe-tidal-cli (very naive) and I am trying to declare it as a repl for flok munshkr/flok#64

The safe-tidal-cli is working locally (I send text to stdin, it sends commands to SuperDirt as it should). I am actually surprised that it found the Tidal library! But, ghci also finds it, since I did cabal install --lib tidal.

[EDIT] connection to flok is working now.

Of course, this repl needs to be made more robust, it needs a better input parser, better error reporting and so on.

[EDIT] and I think it will totally not solve the "make tidal distribution/deploy easier" problem: Hint loads Sound.Tidal.Context, so this needs to be installed first.

Why just don't run it inside a container? I think it's so much easier. Here is my working example: https://github.com/kuhy/tidalbox