Attach in a detached session is refused with words: bare is wrong #args, a name no session has is "no such session"

A detached session's core has no frontend loop to take an Attach, so
the word was asked and never answered: a ctl write of it succeeded
and nothing happened. The core now knows it is a detached session's,
and Attach there says why: bare names no session but itself, a name
with no session behind it is said so, and one that is a session is
told to be attached from a frontend.

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

1 files changed, 17 insertions, 0 deletions

diff --git a/src/pardes.zig b/src/pardes.zig
index f479f44d..4472df8f 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -573,6 +573,20 @@ test "Attach asks for a session and tears nothing down" {
     try std.testing.expect(p.panes[0] != null);
 }
 
+test "Attach in a detached session: bare is wrong #args, a name no session has says so, and nothing is asked" {
+    if (comptime !can_attach) return;
+    const p = try Pardes.init(std.testing.allocator, .{ .tty_only = true, .detached_session = true });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    const pane = p.panes[0].?;
+    try std.testing.expect(p.executeBuiltinLine(0, "Attach"));
+    try std.testing.expect(drainForAttach(p) == null);
+    try std.testing.expectStringStartsWith(pane.msg[0..pane.msg_len], "wrong #args");
+    try std.testing.expect(p.executeBuiltinLine(0, "Attach zz-no-such-session-qq"));
+    try std.testing.expect(drainForAttach(p) == null);
+    try std.testing.expectEqualStrings("Attach: zz-no-such-session-qq: no such session", pane.msg[0..pane.msg_len]);
+}
+
 test "Detach asks the frontend to leave, and says so when there is nothing to leave" {
     if (comptime !can_attach) return; // compiled out where nothing polls `takeAttach` — see `can_attach`
     const gpa = std.testing.allocator;
@@ -4199,6 +4213,9 @@ pub const Options = struct {
     /// load a dump of another instance instead of spawning shells (acme -l)
     load_path: ?[]const u8 = null,
     nested: bool = false,
+    /// The core of a `--detach` session (detached/server.zig): it has no
+    /// terminal of its own, so Attach there is refused with why.
+    detached_session: bool = false,
     startup_config: ?[]const u8 = null,
     ninep_name: []const u8 = "",
     ninep_tcp: ?[]const u8 = null,