From 8469def61324feb5e278f88bebad36af7a0d997e Mon Sep 17 00:00:00 2001
From: Gabriel Schneider <gbrls@0x4200.cafe>
Date: Mon, 28 Sep 2026 23:38:31 -0300
Subject: A send to Python's REPL runs once, the Enter after the paste, not in
 it

A one-line send (print(1)) to Python 3.14 stopped at ... and needed another
Enter: its REPL takes a bracketed paste, and an Enter read in the same read
as the paste is part of the paste, one line or not (checked in a real pty).
Into a REPL that asked for bracketed paste, the Enters (two for an open
block) now wait for its next output, its answer to the paste, or 250 ms
with nothing. fs-test runs python3 in a real pty and checks a one-line exec
prints at once; the docs' pty/data recipe says to send the Enter apart.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 test/fs.py | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

(limited to 'test')

diff --git a/test/fs.py b/test/fs.py
index 890e75f6..81989f88 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -3,6 +3,7 @@ import contextlib
 import fcntl
 import json
 import os
+import shutil
 import signal
 from pathlib import Path
 import subprocess
@@ -466,6 +467,51 @@ def unattended_messages_expire(binary):
             assert not shown(), 'an unattended message outlived MessageLinger'
 
 
+def python_repl_runs_one_line(binary):
+    """A one-line exec sent to Python's own REPL (3.13's pyrepl, which asks
+    for bracketed paste) runs at once, with no second Enter: the Enter
+    reaches it after the paste, not inside it. A real pty, a real python3."""
+    python = shutil.which('python3')
+    if python is None:
+        return
+    version = subprocess.run([python, '-c', 'import sys; print(sys.version_info >= (3, 13))'],
+                             capture_output=True, text=True).stdout.strip()
+    if version != 'True':
+        return
+    with tempfile.TemporaryDirectory(prefix='pardes-repl-') as directory:
+        with session(binary, Path(directory), 'repl') as (client, _):
+            def panes(client):
+                return {int(row.split()[0]) for row in client.read('/index').splitlines()}
+            before = panes(client)
+            client.write('/pane/1/ctl', b'Tty\n')
+            deadline = time.monotonic() + 10
+            while time.monotonic() < deadline and panes(client) == before:
+                time.sleep(.05)
+            tty = max(panes(client) - before)
+            def body():
+                return client.read(f'/pane/{tty}/body').decode('utf-8', 'replace')
+            def wait_for(text, seconds=15):
+                deadline = time.monotonic() + seconds
+                while time.monotonic() < deadline:
+                    if text in body():
+                        return True
+                    time.sleep(.1)
+                return False
+            assert wait_for('$') or wait_for('>'), body()
+            client.write(f'/pane/{tty}/pty/data', python.encode() + b' -q\r')
+            assert wait_for('>>>'), body()
+            client.write(f'/pane/{tty}/ctl', b'Repl python\n')
+            # An exec on the REPL's own body goes to the REPL, as its event
+            # record written back does: an empty range acts on its text.
+            fid = client.open(f'/pane/{tty}/event', 2)
+            try:
+                record = b'MX0 0 0 10 print(6*7)\n'
+                client.rpc(118, struct.pack('<IQI', fid, 0, len(record)) + record)
+                assert wait_for('\n42'), body()
+            finally:
+                client.close(fid)
+
+
 def signal_cleans_up(binary):
     """A detached session told to stop by a signal unlinks its sockets."""
     for sig in [signal.SIGTERM, signal.SIGINT, signal.SIGHUP]:
@@ -487,6 +533,7 @@ def test(binary, quic=False):
     run_file(binary)
     exit_answers(binary)
     unattended_messages_expire(binary)
+    python_repl_runs_one_line(binary)
     signal_cleans_up(binary)
     for options, message in [
         (['--fs'], b'no such option'),
-- 
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