purescript-node / purescript-node-child-process Goto Github PK

Want to know the best way to use this in the browser I heard recently all of purescript changed to es6 fully did this as well?

@joneshf: I just pushed your repository to here - sorry for being impatient.

I just noticed there's no license. Would you be ok with MIT? Is assigning copyright to PureScript ok?

Is there a reason why this library does only has bindings to the async versions of the functions? spawnSync e.g. is missing. purescript-node-fs has split them into a Sync and Async module, maybe an option for this one too?

I noticed the onSpawn handler is missing here.

Adding it is straight-forward though we should use EffectFn2 for this:

export function onSpawn(cp) {
  return function (cb) {
    return function () {
      cp.on("spawn", function () {
        cb();
      });
    };
  };
}

mkOnClose currently adds a callback for the "exit" signal, yet the node documentation clearly states that "close" “is distinct from the 'exit' event, since multiple processes might share the same stdio streams.”.

My intention was that you would be able to put any kind of Stream with any row of effects into the ShareStream constructor, which is what led me to write it as it is now:

data StdIOBehaviour = ShareStream (forall r eff. Stream r eff) | [...]

However, pretty much any Stream you might come across is going to have something in both of these rows, so as far as I can tell, you pretty much have to use unsafeCoerce to actually use this constructor.

Possible solutions:

• Define newtype StdIOBehaviour = StdIOBehaviour Foreign and replace the constructors with normal functions. So eg Pipe would become a normal value pipe :: StdIOBehaviour, and ShareStream would become shareStream :: forall r eff. Stream r eff -> StdIOBehaviour. You lose pattern matching by doing it this way, but it is very simple, and if a user of this library really wanted to do some kind of case analysis, they could use purescript-foreign.
• Keep the ADT and use purescript-exists so that we have something like ShareStream (exists r. exists eff. Stream r eff) (although of course we can't actually do that). I guess it would have to be something like data StdIOBehaviour = ShareStream (Exists (Exists Stream)) which is a bit weird.
• Keep the ADT and define an opaque AnyStream type for use with the ShareStream constructor. So something like this:

-- A stream where you don't know whether it's readable or writable,
-- or what the effects associated with reading/writing are.
foreign import data AnyStream :: *

toAnyStream :: forall r eff. Stream r eff -> AnyStream

-- It is the caller's responsibility to check that the `Stream` being returned
-- has the appropriate type.
unsafeFromAnyStream :: forall r eff. AnyStream -> Stream r eff

data StdIOBehaviour = ShareStream AnyStream | [...]

We need to add a better wrapper around ChildProcess and Node Streams

• we'll need to move from pulp to spago to be able to use purescript-node-streams-aff
• add Aff module with improved API

Related purescript-deprecated/purescript-node-streams-aff#8

Currently, Node.ChildProcess.spawn with a non-existent executable will return a ChildProcess which isn't "real". For example, its pid will be undefined. This is not ideal.

Currently, you have to handle this by calling onError. Unfortunately, onError is used for other failure conditions that do not happen immediately; see the Node docs.

It's not currently clear to me how best to handle this.

See also joneshf/purescript-node-child-process#4

For each of stdin, stdout, and stderr, the stream will be accessible on the child process object if and only if "pipe" was passed as the relevant stdio options. For example, if you did var child = spawn(cmd, args, { stdio: ["pipe", someStream, "pipe"]}, then you would be able to read child.stderr and write child.stdin, but child.stdout would be null.

Currently, we throw an error if you try to access one of the standard streams after spawning it and passing something other than Pipe for that stream. It might be nice to work out how to do this in a safer way than just failing at runtime, if possible.

when I try to write custom something like

import Node.Process as Node.Process


noInputOnlyOutput = [Just Ignore, Just (ShareStream Node.Process.stdout), Just Pipe]

I cannot

https://github.com/purescript-node/purescript-node-process/blob/88871d84a69f47dd2d1d9eccd7cc942be4457d46/src/Node/Process.purs#L125-L126

[1/1 TypesDoNotUnify] webpack/NextjsWebpack/Utils/OnFilesChangedRunCommand.purs:26:53

  26  noInputOnlyOutput = [Just Ignore, Just (ShareStream Node.Process.stdout), Just Pipe]
                                                          ^^^^^^^^^^^^^^^^^^^

  Could not match type

    ( write :: Write
    )

  with type

    r0

it also cannot be rewritten with Exists

data StdIOBehaviour
  = Pipe
  | Ignore
  | ShareStream (Exists Stream)
  | ShareFD FS.FileDescriptor

  Could not match kind

    # Type

  with kind

    Type

But it's Unit