A second pardes --detach=NAME while NAME runs says "a session named NAME is already running" and exits 1, with no error trace

The second session built its whole core before its bind failed, then
returned an error that main printed with a Zig error-return trace. The
name is now checked first: a live session's socket is said, and the
process exits 1 having made nothing.

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

2 files changed, 20 insertions, 1 deletions

diff --git a/src/detached/server.zig b/src/detached/server.zig
index 78b85836..588912bb 100644
--- a/src/detached/server.zig
+++ b/src/detached/server.zig
@@ -1238,6 +1238,17 @@ pub const detached_cols = 160;
 pub const detached_rows = 50;
 
 pub fn run(init: std.process.Init, opts: pardes.Options, name: []const u8) !void {
+    // A name a live session holds: said, exit 1, before anything is made
+    // (no error trace, no second session racing the first for the socket).
+    if (comptime supported) {
+        var path_buf: [path_max]u8 = undefined;
+        if (sessionPath(&path_buf, name)) |path| if (ninep_io.statNoFollow(path) != null and alive(path)) {
+            var said: [path_max + 64]u8 = undefined;
+            const text = std.fmt.bufPrint(&said, "pardes: a session named {s} is already running\n", .{name}) catch "pardes: a session of that name is already running\n";
+            std.Io.File.stderr().writeStreamingAll(init.io, text) catch {};
+            std.process.exit(1);
+        };
+    }
     const gpa = init.gpa;
     const allocs = pardes.memory.init(gpa);
     defer pardes.memory.deinit();
@@ -1282,7 +1293,7 @@ pub fn run(init: std.process.Init, opts: pardes.Options, name: []const u8) !void
     try session.initAsync();
     if (!session.listen(name)) {
         try std.Io.File.stderr().writeStreamingAll(init.io, "pardes: could not bind a detached session socket\n");
-        return error.NoSocket;
+        std.process.exit(1);
     }
 
     session.ninep = ninep_io.listen(init.io, gpa, core, opts.ninep_name, name, opts.ninep_tcp, opts.ninep_quic);
diff --git a/test/fs.py b/test/fs.py
index 2782407d..8d830c48 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -1306,6 +1306,14 @@ def test(binary, quic=False):
         # opened is deleted, as an $EDITOR must; one on a file already open
         # waits on that pane; a session that goes away ends it with 1.
         with session(binary, root, 'wait') as (client, address):
+            # A second --detach of a name a live session holds: said, exit 1,
+            # no Zig error trace.
+            second_env = {k: v for k, v in os.environ.items() if not k.startswith('PARDES_')}
+            second_env.update(HOME=str(root), XDG_RUNTIME_DIR=str(root))
+            second = subprocess.run([binary, '--detach=wait'], cwd=root, env=second_env,
+                                    stdout=subprocess.DEVNULL, stderr=subprocess.PIPE, timeout=20)
+            assert second.returncode == 1, second
+            assert second.stderr == b'pardes: a session named wait is already running\n', second.stderr
             status = dict(line.split(maxsplit=1) for line in client.read('/status').decode().splitlines())
             env = {k: v for k, v in os.environ.items() if k != 'PARDES_FORWARD_LOOK'}
             env.update(PARDES_9P=str(address), PARDES_PANE='1', PARDES_PID=status['pid'])