A Rename that previews other files answers its preview pane to the 9P write that asked it, and says on the message row that it previewed and applied nothing

A multi-file Rename filled a +Search preview but the waiting exec write
answered the pane it was asked from, and nothing was said. lspResponse
now notes the pane it filled (fs.lsp_result); the write that waited for
the answer reads that pane back, as a look or an exec answers the pane
it went to, and the message row says `Rename: N edit(s) across files,
previewed, not applied`.

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

4 files changed, 37 insertions, 0 deletions

diff --git a/src/9p_io.zig b/src/9p_io.zig
index ea3f799c..a4340ddf 100644
--- a/src/9p_io.zig
+++ b/src/9p_io.zig
@@ -317,7 +317,20 @@ pub const Listener = struct {
         if (core.effects_len != 0) pardes.turn.awaitSettled(epoch);
         if (core.fs.lsp_answer_at) |n| {
             core.fs.lsp_answer_at = null;
+            core.fs.lsp_result = null;
             pardes.turn.awaitLsp(n);
+            // The answer filled a pane (a Rename's preview): that is what
+            // this write's open reads back, as look and exec answer.
+            if (l.core == core) if (core.fs.lsp_result) |serial| {
+                core.fs.lsp_result = null;
+                core.fs.results[0] = serial;
+                core.fs.results_len = 1;
+                if (pardes.ctlfs.openOf(core, req)) |o| {
+                    o.results.list[0] = serial;
+                    o.results.len = 1;
+                    o.results.read = 0;
+                }
+            };
         }
         core.fs.write_waits = false;
         // ponytail: one slot, so a failure of another client's effects that
diff --git a/src/fs.zig b/src/fs.zig
index 0c04e873..7d6b0d71 100644
--- a/src/fs.zig
+++ b/src/fs.zig
@@ -1529,6 +1529,9 @@ pub const Namespace = struct {
     /// A 9P write asked a language server something: the answer count it
     /// waits to change (`turn.lsp_answers`), so its failure is the write's.
     lsp_answer_at: ?u64 = null,
+    /// The pane a language answer filled (a Rename's preview): what the
+    /// waiting 9P write answers once it is in (9p_io).
+    lsp_result: ?u32 = null,
     /// The most a Twrite of the request being served can carry (msize less
     /// its header), 0 when unknown: a write shorter than it is the whole of
     /// what its client wrote, one that fills it may be cut and go on.
diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index b17f150a..f0dab28d 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -4105,3 +4105,15 @@ test "Tty+bash on a pane ctl is Tty with its argument, as exec and the tag take
     try testing.expectEqual(Status.ok, r.reply.status);
     try testing.expect(r.spawned);
 }
+
+test "a Rename that reaches other files previews them, says so, and is the pane a waiting write answers" {
+    const p = try withFile(testing.allocator, "x\n");
+    defer p.deinit();
+    const id = p.active;
+    p.fs.lsp_result = null;
+    p.lspRequest(id, .rename, "sum");
+    p.lspResponse(p.lsp_wait.?.id, "lib.rs:2:8 sum\nmain.rs:4:13-15 sum\n");
+    const preview = p.panes[p.panes[id].?.search_pane.?].?;
+    try testing.expectEqual(preview.serial, p.fs.lsp_result.?);
+    try testing.expect(th.logHas(p, "Rename: 2 edit(s) across files, previewed, not applied"));
+}
diff --git a/src/pardes.zig b/src/pardes.zig
index f5001797..ca0980f4 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -6764,6 +6764,15 @@ pub const Pardes = struct {
             p.reportError(w.pane, "language response", err);
             return;
         };
+        // What a 9P write that asked it answers: the pane the rows are in
+        // (a multi-file Rename's preview), not the pane it was asked from.
+        if (pane.search_pane) |rid| if (p.panes[rid]) |rp| {
+            p.fs.lsp_result = rp.serial;
+        };
+        if (w.kind == .rename) {
+            var said_buf: [96]u8 = undefined;
+            p.setMessage(w.pane, std.fmt.bufPrint(&said_buf, "Rename: {d} edit(s) across files, previewed, not applied", .{nrows}) catch "Rename: previewed");
+        }
         if (panes.Output.traits(from).jumps) {
             const result = p.panes[pane.search_pane orelse return] orelse return;
             const file = pane.file orelse return;