Column serials go on across a Restore as pane serials do: a restored column never takes a serial the old session handed out

A Restore carried next_serial over for panes but started column serials at
1 again. So a restored column could take the serial a deleted column had,
and a script holding col/<n> from before the Restore would find a different
column there. The column counter is now carried over like the pane one, and
restoredcol maps each old serial to a fresh one.

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

2 files changed, 17 insertions, 0 deletions

diff --git a/src/dump.zig b/src/dump.zig
index 2d3c2593..1cc115be 100644
--- a/src/dump.zig
+++ b/src/dump.zig
@@ -852,6 +852,9 @@ fn initDump(gpa: std.mem.Allocator, opts: Options, zon_bytes: []const u8, previo
     errdefer p.deinit();
     if (previous) |old| {
         p.next_serial = old.next_serial;
+        // Columns as panes: a restored one takes a fresh serial, never one
+        // a column of the old session had, living or deleted.
+        p.next_column_serial = old.next_column_serial;
         p.lsp_seq = old.lsp_seq;
         p.pipe.seq = old.pipe.seq;
         p.cell_pixels = old.cell_pixels;
diff --git a/src/ninep/events.zig b/src/ninep/events.zig
index fe7af77e..906e7a9a 100644
--- a/src/ninep/events.zig
+++ b/src/ninep/events.zig
@@ -1176,6 +1176,20 @@ test "a Dump written and a Restore made are in the log, with their files" {
     try testing.expect(std.mem.endsWith(u8, log.bytes, try std.fmt.bufPrint(&want, "restoredcol {d} {d}\n", .{ pardes.layout.columnSerial(p, 0), pardes.layout.columnSerial(restored, 0) })));
 }
 
+test "a Restore gives columns fresh serials, past every serial the old session handed out" {
+    const p = try withFile(testing.allocator, "one\n");
+    defer p.deinit();
+    const first = pardes.layout.columnSerial(p, 0);
+    // Serials spent on columns since deleted.
+    p.next_column_serial += 5;
+    const spent = p.next_column_serial;
+    try dump.dumpState(p);
+    const restored = try dump.restore(p, p.dump_out.?, "/tmp/pardes.dump.zon");
+    defer restored.deinit();
+    for (0..restored.ncol) |c| try testing.expect(pardes.layout.columnSerial(restored, c) >= spent);
+    try testing.expect(pardes.layout.columnSerial(restored, 0) != first);
+}
+
 test "opens of the log share the open records, and a closed one frees its record" {
     const gpa = testing.allocator;
     const p = try withFile(gpa, "x\n");