--wait waits on the pane its look answered, read on the look's own open, not one found again by name in /index

The forwarded look was a write and nothing more, and --wait then
looked its file up in /index. /index shows names escaped (`\\` for a
backslash, `\xNN`), so a file named with one matched no pane and
--wait exited 0 at once, as if the pane were already closed. The look
is now asked on one open (Client.ask) and its answer is the pane
waited on; /index by name stays only for a look that answers none.

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

2 files changed, 27 insertions, 6 deletions

diff --git a/src/main.zig b/src/main.zig
index 6c46b22c..de501047 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -281,11 +281,12 @@ fn forwardWords(err: anyerror, buf: []u8) []const u8 {
 /// connection ends with the session -- exit 1.
 fn waitForDel(io: std.Io, gpa: std.mem.Allocator, dial: []const u8, path: []const u8, known: ?u32) noreturn {
     _ = io;
-    // The pane this launch made (a name not there yet) is known by its
-    // serial; one a look opened or went to is found by its file. Found by
-    // none after the look went there, it was closed already: that is the
-    // end being waited for, not a failure (a pane closed between the look
-    // and this read made `--wait` exit 1 before).
+    // The pane this launch made (a name not there yet), or the one its
+    // look answered, is known by its serial; one the look answered none
+    // for is found by its file. Found by none after the look went there,
+    // it was closed already: that is the end being waited for, not a
+    // failure (a pane closed between the look and this read made `--wait`
+    // exit 1 before).
     const serial = known orelse found: {
         const first = ninep_io.Client.read(gpa, dial, "/index", "/index") catch std.process.exit(1);
         defer gpa.free(first);
@@ -660,7 +661,11 @@ fn nativeMain(init: std.process.Init) !void {
         if (found_path != null) {
             var command_buf: [8192]u8 = undefined;
             const command = std.fmt.bufPrint(&command_buf, "{s}{s}\n", .{ path, word[target.path.len..] }) catch |err| Refuse.with(init.io, word, err);
-            ninep_io.Client.write(arena, parent.dial, look, command) catch |err| Refuse.with(init.io, word, err);
+            // The pane it went to, read on the open that asked (another
+            // client's look meanwhile is not this one's): what --wait waits on.
+            const went = ninep_io.Client.ask(arena, parent.dial, look, command) catch |err| Refuse.with(init.io, word, err);
+            var rows = std.mem.tokenizeAny(u8, went, " \n");
+            if (rows.next()) |row| made_serial = std.fmt.parseInt(u32, row, 10) catch null;
         } else {
             const made = ninep_io.Client.read(arena, parent.dial, "/pane/new", "/pane/new") catch |err| Refuse.with(init.io, word, err);
             const serial = std.fmt.parseInt(u32, std.mem.trim(u8, made, " \n"), 10) catch |err| Refuse.with(init.io, word, err);
diff --git a/test/fs.py b/test/fs.py
index fcd779d1..483ef320 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -1395,6 +1395,22 @@ def test(binary, quic=False):
             assert time.monotonic() - deleted < .05, time.monotonic() - deleted
             assert second.wait(timeout=5) == 0
             assert edited.read_bytes() == b'edited\n'
+            # --wait waits on the pane its look answered, on the look's own
+            # open: a name /index shows escaped (a backslash is `\\` there)
+            # is still the pane waited on, not one already gone.
+            odd = root / 'wait\\odd.txt'
+            odd.write_bytes(b'odd\n')
+            before = serials()
+            waiting = subprocess.Popen([binary, '--wait', str(odd)], cwd=root, env=env,
+                                       stdout=subprocess.DEVNULL, stderr=subprocess.PIPE)
+            deadline = time.monotonic() + 3
+            while not serials() - before and time.monotonic() < deadline:
+                time.sleep(.01)
+            odd_pane, = serials() - before
+            time.sleep(.5)
+            assert waiting.poll() is None, waiting.stderr.read()
+            client.remove(f'/pane/{odd_pane}')
+            assert waiting.wait(timeout=5) == 0
             # A name not there yet opens a pane named it, as acme's B does,
             # and Save creates it: git's and fish's temporary files are.
             fresh = root / 'wait new.txt'