New and Tty run at /tagexec and a column's exec, and with no pane at all

The words New and Tty make a pane in the session's directory, and fs.md
already has them run at a tag no pane owns. But /tagexec refused New as a
pane's word, since the workspace tag does not hold it. Every header exec
also failed ENOENT when no pane was left, and Tty gave up when it had no
pane to take a directory from. Now New and Tty are every tag's words.
A header exec with no pane runs at the stand-in, as a click in the empty
window's tag does, and Tty with no pane asking starts in the session's
directory, as New's scratch does.

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

1 files changed, 28 insertions, 1 deletions

diff --git a/src/ninep/cols.zig b/src/ninep/cols.zig
index b1ca954c..4db78584 100644
--- a/src/ninep/cols.zig
+++ b/src/ninep/cols.zig
@@ -205,7 +205,8 @@ pub fn writeExec(p: *Pardes, req: Req, serial: ?u32) Reply {
         if (paneWord(line, if (serial == null) pardes.config.topbar_str else tagline.column_tag_default))
             return pardes.ctlfs.ctl.refuseTo(p, req, "not a session control message", line, "pane/<n>/ctl");
         const col = if (serial) |s| layout.columnBySerial(p, s) orelse return Reply.fail(req.tag, E.NOENT) else null;
-        if (p.panes[p.active] == null) return Reply.fail(req.tag, E.NOENT);
+        // With no pane at all, a word runs at the stand-in, as a click in
+        // the empty window's tag does (runBuiltinFrom).
         p.exec_column = col;
         defer p.exec_column = null;
         p.exec_header = true;
@@ -260,6 +261,8 @@ fn paneWord(line: []const u8, own: []const u8) bool {
     const word = cmd[0 .. std.mem.indexOfAny(u8, cmd, " \t+") orelse cmd.len];
     const b = std.meta.stringToEnum(pardes.builtins.registry.Builtin(), word) orelse return false;
     if (pardes.builtins.registry.scope(b) == .session) return false;
+    // A new pane is every tag's to make, in the session's directory.
+    if (b == .New or b == .Tty) return false;
     var words = std.mem.tokenizeScalar(u8, own, ' ');
     while (words.next()) |w| if (std.mem.eql(u8, w, word)) return false;
     return true;
@@ -280,6 +283,29 @@ test "a pane's word written to /tagexec or a column's exec is refused, and acts
     try testing.expectEqual(tree.Status.ok, th.wr(p, col_exec, "New\n").reply.status);
 }
 
+test "New and Tty run at /tagexec and a column's exec, with no pane at all too" {
+    const p = try th.withFile(testing.allocator, "x\n");
+    defer p.deinit();
+    const tagexec = @intFromEnum(tree.TopFile.tagexec);
+    const col_exec = tree.Node.ofCol(layout.columnSerial(p, 0), .exec);
+    for ([_]u64{ tagexec, col_exec }) |node| for ([_][]const u8{ "New\n", "Tty\n" }) |line| {
+        const before = p.next_serial;
+        try testing.expectEqual(tree.Status.ok, th.wr(p, node, line).reply.status);
+        try testing.expectEqual(before + 1, p.next_serial);
+    };
+    // Every pane gone: the workspace tag makes one all the same.
+    for ([_][]const u8{ "New\n", "Tty\n" }) |line| {
+        while (p.ncol > 0) {
+            const first = p.panes[p.col_panes[0][0]].?.serial;
+            _ = th.wr(p, tree.Node.of(first, .ctl), "delete\n");
+            if (p.anyPane() == null) break;
+        }
+        try testing.expect(p.anyPane() == null);
+        try testing.expectEqual(tree.Status.ok, th.wr(p, tagexec, line).reply.status);
+        try testing.expect(p.anyPane() != null);
+    }
+}
+
 test "every pane word a tag no pane owns does not hold is refused there, Edit included, and the pane is untouched" {
     const p = try th.withFile(testing.allocator, "keep me\n");
     defer p.deinit();
@@ -292,6 +318,7 @@ test "every pane word a tag no pane owns does not hold is refused there, Edit in
         var checked: usize = 0;
         for (std.enums.values(Builtin)) |b| {
             if (pardes.builtins.registry.scope(b) == .session) continue;
+            if (b == .New or b == .Tty) continue; // every tag's
             var owned = false;
             var words = std.mem.tokenizeScalar(u8, tag_file.own, ' ');
             while (words.next()) |w| owned = owned or std.mem.eql(u8, w, @tagName(b));