Reline misbehaves on Windows under stdin redirection

[rschmitt]

When stdin is redirected (such that $stdin.isatty is false), Readline.readline hangs on Windows. This one-line reproducer can be run in PowerShell to illustrate the problem (this is with Ruby 4.0.5):

$null | ruby -e "require 'readline'; STDERR.puts %Q{gate=#{Reline::IOGate.class}}; STDERR.puts %Q{`$stdin.isatty=#{`$stdin.isatty}}; p Readline.readline('> ')"

This prints the following and then goes into an infinite loop until killed with Ctrl-C:

gate=Reline::Windows
$stdin.isatty=false
>

Worse still, piping a non-null string ('input' | ruby -e ...) or even multiple lines (@('line1', 'line2') | ruby -e ...) results in the same behavior, apparently because Reline::Windows is reading directly from the console handle rather than the stdin stream.

Setting $env:TERM='dumb' (as per #616) shows the expected behavior: the program immediately reads EOF and returns:

$env:TERM='dumb'; $null | ruby -e "require 'readline'; STDERR.puts %Q{gate=#{Reline::IOGate.class}}; STDERR.puts %Q{`$stdin.isatty=#{`$stdin.isatty}}; p Readline.readline('> ')"; ri Env:\TERM
gate=Reline::Dumb
$stdin.isatty=false
> > nil

Non null inputs render strangely, but they still read correctly:

$env:TERM='dumb'; 'input' | ruby -e "require 'readline'; STDERR.puts %Q{gate=#{Reline::IOGate.class}}; STDERR.puts %Q{`$stdin.isatty=#{`$stdin.isatty}}; p Readline.readline('> ')"; ri Env:\TERM
gate=Reline::Dumb
$stdin.isatty=false
> iininpinpuinput> input
"input"