allow redirect_std* to devnull (JuliaLang#36136) (JuliaLang#36146)

base/stream.jl

@@ -1098,6 +1098,15 @@ for (x, writable, unix_fd, c_symbol) in
  ($f)($(writable ? :write : :read))
  return (read, write)
  end
+ function ($f)(::DevNull)
+ global $x
+ nulldev = @static Sys.iswindows() ? "NUL" : "/dev/null"
+ handle = open(nulldev, write=$writable)
+ $(_f)(handle)
+ close(handle) # handle has been dup'ed in $(_f)
+ $x = devnull
+ return devnull
+ end
  end
 end
 
@@ -1115,7 +1124,7 @@ elsewhere.
 If called with the optional `stream` argument, then returns `stream` itself.
 
 !!! note
- `stream` must be a `TTY`, a `Pipe`, or a socket.
+ `stream` must be an `IOStream`, a `TTY`, a `Pipe`, a socket, or `devnull`.
 """
 redirect_stdout
 
@@ -1125,7 +1134,7 @@ redirect_stdout
 Like [`redirect_stdout`](@ref), but for [`stderr`](@ref).
 
 !!! note
- `stream` must be a `TTY`, a `Pipe`, or a socket.
+ `stream` must be an `IOStream`, a `TTY`, a `Pipe`, a socket, or `devnull`.
 """
 redirect_stderr
 
@@ -1137,7 +1146,7 @@ Note that the order of the return tuple is still `(rd, wr)`,
 i.e. data to be read from [`stdin`](@ref) may be written to `wr`.
 
 !!! note
- `stream` must be a `TTY`, a `Pipe`, or a socket.
+ `stream` must be an `IOStream`, a `TTY`, a `Pipe`, a socket, or `devnull`.
 """
 redirect_stdin
 

test/spawn.jl

@@ -255,6 +255,19 @@ end
  end
 end
 
+# issue #36136
+@testset "redirect to devnull" begin
+ @test redirect_stdout(devnull) do; println("Hello") end === nothing
+ @test redirect_stderr(devnull) do; println(stderr, "Hello") end === nothing
+ # stdin is unavailable on the workers. Run test on master.
+ ret = Core.eval(Main, quote
+ remotecall_fetch(1) do
+ redirect_stdin(devnull) do; read(stdin, String) end
+ end
+ end)
+ @test ret == ""
+end
+
 # Test that redirecting an IOStream does not crash the process
 let fname = tempname(), p
  cmd = """