do block form of redirect_stdio

[vtjnash]

Julip (with code!): do block form of redirect_stdio

Inspired by samuelcolvin/JuliaByExample#6 (comment)

Usage examples:

redirect_stdio() do
  println("this goes to stdout")
end
redirect_stdio(stdout=false) do
  println("this goes to old stdout")
  println(STDERR, "this goes to new stderr")
end

Implementation:

function redirect_stdio(fn; stdin::Union(Bool,IO)=true, stdout::Union(Bool,IO)=true, stderr::Union(Bool,IO)=true)
  orig = (STDIN,STDOUT,STDERR)
  stdin_out = stdout_in = stderr_in = false
  try
    if stdin === true
        stdin_out = redirect_stdin()[2]
    elseif isa(stdin,IO)
        stdin_out = redirect_stdin(stdin)[2]
    end
    if stdout === true
        stdout_in = redirect_stdout()[1]
    elseif isa(stdout,IO)
        stdout_in = redirect_stdout(stdout)[1]
    end
    if stderr === true
        stderr_in = redirect_stderr()[1]
    elseif isa(stderr,IO)
        stderr_in = redirect_stderr(stderr)[1]
    end
    fn()
  finally
    stdin_out !== false && redirect_stdin(orig[1])
    stdout_in !== false && redirect_stdout(orig[2])
    stderr_in !== false && redirect_stderr(orig[3])
    stdin === true && close(stdin_out)
    stdout === true && close(stdout_in)
    stderr === true && close(stderr_in)
  end
end

thoughts? bugs?

[kmsquire]

In your example, I assume you mean

println(stderr, "this goes to new stderr")

[vtjnash]

what? I can't have a program that even executes my sentences to find bugs? (fixed above)

[vtjnash]

This needs to return stdin / stout / stderr

[JeffBezanson]

Why is this a 0.3 issue?

[vtjnash]

because I can merge this PR if the concept is approved of

[JeffBezanson]

I'm not convinced.

[tkelman]

redirect_stdio doesn't seem to exist any more.

[vtjnash]

it's shorthand for redirect_stderr / redirect_stdin / redirect_stdout

[tkelman]

Misread, sorry. Not going to be backported and not release blocking, so not a milestone issue.

[timholy]

Closed by #18165