effect-deprecated/process

A simple library for interacting with external processes and command-line programs via Effect-TS (port of zio-process)

Welcome to Effect-TS - Process

Please follow up to: https://github.com/Effect-TS/process/tree/master/packages/process

Install

We recommend the usage of yarn and if you have yarn workspaces that handles by default hoisting of dependencies:

yarn add @effect-ts/core @effect-ts/node @effect-ts/process

process's Issues

Redirect stderr to stdout when Command.redirectErrorStream is true

Is your feature request related to a problem? Please describe.

The redirectErrorStream property on a StandardCommand should cause the stderr stream to be redirected to stdout. At the moment, this is not implemented.

Describe the solution you'd like

If we have a shell script called both-streams.sh such as this:

#!/bin/bash

function echoerr {
  echo "$@" 1>&2
}

echo "stdout1"
echoerr "stderr1"

echo "stdout2"
echoerr "stderr2"

then the redirectErrorStream combinator should cause the stderr stream to be redirected to stdout.

  it("should merge stderr into stdout when redirectErrorStream is true", () =>
    T.gen(function* (_) {
      const command = pipe(
        Command.command("./both-streams-test.sh"),
        Command.workingDirectory("packages/process/test/bash"),
        Command.redirectErrorStream(true)
      )
  
      const { stderr, stdout } = yield* _(
        pipe(
          T.do,
          T.bind("process", () => Command.run(command)),
          T.bind("stdout", ({ process }) =>
            ProcessStream.string(Process.stdout(process))
          ),
          T.bind("stderr", ({ process }) =>
            ProcessStream.string(Process.stderr(process))
          )
        )
      )
  
      expect(stderr).toBe("")
      expect(stdout).toBe("stdout1\nstderr1\nstdout2\nstderr\n")
    }))

Describe alternatives you've considered

None

Additional context

Based on this discussion on StackOverflow, it doesn't seem possible to ensure correct ordering of the stdout and stderr output streams.

Also for context:

• Issue related to this in libuv
• Issue related to this in node (archive)

Fix errors throw when using `Command.inheritIO`

Allow for capturing stdout and stderr separately

Is your feature request related to a problem? Please describe.

At the moment, if one would like to capture the output of stdout and stderr separately, it must be done in parallel. For example:

This will properly capture stdout and stderr into a Tuple.

pipe(
  Command.command("ls"),
  Command.run,
  T.chain((process) =>
    T.zipPar_(
      ProcessStream.string(Process.stdout(process)),
      ProcessStream.string(Process.stderr(process))
    )
  )
)

but this will capture only stdout

pipe(
  T.do,
  T.bind("process", () => Command.command("ls")),
  T.bind("stdout", ({ process }) => ProcessStream.string(Process.stdout(process))),
  T.bind("stderr", ({ process }) => ProcessStream.string(Process.stderr(process)))
)

Describe the solution you'd like

To be able to capture stdout and stderr separately even when not running in parallel (as is done in the original implementation).

Describe alternatives you've considered

None

Additional context

I believe the root cause of the issue is how the NodeJS ReadableStream is actually drained here. I am open to suggestions on alternative approaches. For reference, here is the original implementation.