REPL test: fix destructive kill timer to do something

Previously, isopen(t) was guaranteed to be false, and the timer would just quietly expire

stdlib/REPL/test/repl.jl

@@ -16,8 +16,26 @@ include(joinpath(BASE_TEST_PATH, "testenv.jl"))
 include("FakeTerminals.jl")
 import .FakeTerminals.FakeTerminal
 
+
+function kill_timer(delay)
+ # Give ourselves a generous timer here, just to prevent
+ # this causing e.g. a CI hang when there's something unexpected in the output.
+ # This is really messy and leaves the process in an undefined state.
+ # the proper and correct way to do this in real code would be to destroy the
+ # IO handles: `close(stdout_read); close(stdin_write)`
+ test_task = current_task()
+ function kill_test(t)
+ # **DON'T COPY ME.**
+ # The correct way to handle timeouts is to close the handle:
+ # e.g. `close(stdout_read); close(stdin_write)`
+ schedule(test_task, "hard kill repl test"; error=true)
+ print(stderr, "WARNING: attempting hard kill of repl test after exceeding timeout\n")
+ end
+ return Timer(kill_test, delay)
+end
+
 # REPL tests
-function fake_repl(f; options::REPL.Options=REPL.Options(confirm_exit=false))
+function fake_repl(@nospecialize(f); options::REPL.Options=REPL.Options(confirm_exit=false))
  # Use pipes so we can easily do blocking reads
  # In the future if we want we can add a test that the right object
  # gets displayed by intercepting the display
@@ -31,6 +49,7 @@ function fake_repl(f; options::REPL.Options=REPL.Options(confirm_exit=false))
  repl = REPL.LineEditREPL(FakeTerminal(input.out, output.in, err.in), true)
  repl.options = options
 
+ hard_kill = kill_timer(900) # Your debugging session starts now. You have 15 minutes. Go.
  f(input.in, output.out, repl)
  t = @async begin
  close(input.in)
@@ -40,6 +59,7 @@ function fake_repl(f; options::REPL.Options=REPL.Options(confirm_exit=false))
  @test read(err.out, String) == ""
  #display(read(output.out, String))
  Base._wait(t)
+ close(hard_kill)
  nothing
 end
 
@@ -69,14 +89,6 @@ fake_repl() do stdin_write, stdout_read, repl
  notify(b)
  wait(c)
 
- # Give ourselves a generous timer here, just to prevent
- # this causing e.g. a CI hang when there's something unexpected
- # in the output.
- t = Timer(200) do t
- isopen(t) || return
- error("Stuck waiting for repl test")
- end
-
  # Latex completions
  write(stdin_write, "\x32\\alpha\t")
  readuntil(stdout_read, "α")
@@ -247,14 +259,12 @@ fake_repl() do stdin_write, stdout_read, repl
  write(stdin_write, "1+1\n") # populate history with a trivial input
  readline(stdout_read)
  write(stdin_write, "\e[A\n")
- t = Timer(10) do t
- isopen(t) || return
- error("Stuck waiting for the repl to write `1+1`")
+ let t = kill_timer(60)
+ # yield make sure this got processed
+ readuntil(stdout_read, "1+1")
+ readuntil(stdout_read, "\n\n")
+ close(t) # cancel timeout
  end
- # yield make sure this got processed
- readuntil(stdout_read, "1+1")
- close(t)
- readuntil(stdout_read, "\n\n")
 
  # Issue #10222
  # Test ignoring insert key in standard and prefix search modes
@@ -287,11 +297,12 @@ fake_repl() do stdin_write, stdout_read, repl
  # Now, down arrow, enter, should get us back to 2
  write(stdin_write, "\e[B\n")
  readuntil(stdout_read, s2)
- close(t)
 
  # Close REPL ^D
  write(stdin_write, '\x04')
  Base._wait(repltask)
+
+ nothing
 end
 
 function buffercontents(buf::IOBuffer)