Every pane pardes spawns gets $PARDES_MOUNT, the session's own directory under 9ns --mntgen ($NINE_MOUNT/pardes/<name>), unset when it is not known

9ns says --mntgen with NINE_MNTGEN=1 (cloud9). Under `9ns --unix` the
mount is the server it dialled, never this session (its socket does not
exist until it starts), so it stays unset there; scripts fall back to
`9p -a "unix!$PARDES_9P"`. Nothing is statted: the name comes from the
session's socket and the environment. selfmount checks both modes.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 48 insertions, 0 deletions

diff --git a/test/selfmount.py b/test/selfmount.py
index 8d78487d..0111e6ac 100644
--- a/test/selfmount.py
+++ b/test/selfmount.py
@@ -27,6 +27,46 @@ sys.path.insert(0, str(Path(__file__).resolve().parent))
 from ninep import Client
 
 
+def unix_mount(ns, binary, served, env, name, fixture):
+    """A second editor under `9ns --unix <the first's socket>`, on the
+    fixture (a command runs from a file's pane, not a terminal's): what its
+    command pane sees in $PARDES_MOUNT."""
+    second = name + 'u'
+    sock = f'{os.environ["XDG_RUNTIME_DIR"]}/pardes-9p-{second}.sock'
+    out = Path(f'/tmp/{second}.mount')
+    env = dict(env, PARDES_DUMP=f'/tmp/{second}.dump.zon')
+    pid, master = pty.fork()
+    if pid == 0:
+        os.execve(ns, ['9ns', '--unix', served, '--', binary, '--tty', '--9p=' + second, str(fixture)], env)
+    fcntl.ioctl(master, termios.TIOCSWINSZ, struct.pack('HHHH', 30, 100, 0, 0))
+    os.set_blocking(master, False)
+    try:
+        deadline = time.monotonic() + 30
+        while time.monotonic() < deadline and not out.exists():
+            try:
+                os.read(master, 65536)
+            except OSError:
+                pass
+            if os.path.exists(sock) and not out.with_suffix('.sent').exists():
+                time.sleep(.3)
+                with Client(sock) as client:
+                    client.write('/ctl', b'Shell sh\n')
+                    client.write('/exec', f'echo "${{PARDES_MOUNT-unset}}" > {out}.tmp; mv {out}.tmp {out}\n'.encode())
+                out.with_suffix('.sent').touch()
+            time.sleep(.1)
+        return out.read_text().strip() if out.exists() else 'timeout'
+    finally:
+        os.kill(pid, signal.SIGTERM)
+        time.sleep(.2)
+        try:
+            os.kill(pid, signal.SIGKILL)
+        except ProcessLookupError:
+            pass
+        os.waitpid(pid, 0)
+        for path in (out, out.with_suffix('.sent'), Path(f'/tmp/{second}.dump.zon')):
+            path.unlink(missing_ok=True)
+
+
 def run(binary):
     ns = shutil.which('9ns') or str(Path.home() / '.local/bin/9ns')
     runtime = os.environ.get('XDG_RUNTIME_DIR')
@@ -128,6 +168,14 @@ def run(binary):
                         return exits[-1].split()[2]
                     time.sleep(.1)
                 return 'timeout'
+            # A pane's command finds the session's own directory in
+            # $PARDES_MOUNT (9ns --mntgen says NINE_MNTGEN=1).
+            check(run(f'test "$PARDES_MOUNT" = {mount} && grep -q . "$PARDES_MOUNT/index"\n'.encode()) == '0',
+                  '$PARDES_MOUNT is the session under the mntgen mount, and it answers')
+            # Under `9ns --unix` the mount is another server, never this
+            # session: a second editor started there leaves it unset.
+            seen_mount = unix_mount(ns, binary, sock, env, name, fixture)
+            check(seen_mount == 'unset', f'under 9ns --unix $PARDES_MOUNT is unset ({seen_mount!r})')
             # Followed from before the burst: a fresh open of the log reads
             # only what its 64 KiB ring still holds, which a burst this size
             # outgrows, and a follower the ring outruns reads `lost N`, so