A refused /pager write leaves its open no answer, not the +Pager it answered before

writePager emptied the answer only once the directory had passed, so a
read after a refused write on the same open still gave the last write's
serial. It is emptied first, as a refused look or exec leaves none.

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

1 files changed, 5 insertions, 1 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index f0dab28d..89d438df 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -648,6 +648,8 @@ pub fn readRoot(p: *Pardes, req: Req) Reply {
 /// session's) gets its one +Pager, made or emptied; the serial is what a
 /// read of this same open answers, never another client's.
 pub fn writePager(p: *Pardes, req: Req) Reply {
+    // A refused write leaves its open no answer, not the last one's.
+    p.fs.results_len = 0;
     var it = Messages.init(p, req.data);
     const line = it.next() orelse "";
     // Words 9ns maps back to EINVAL (`invalid`), as every refusal here.
@@ -661,7 +663,6 @@ pub fn writePager(p: *Pardes, req: Req) Reply {
     }
     if (comptime pardes.hosted) if (dir.len > 0) if (pardes.filesystem.localPath(dir)) |local| if (!exec_line.isDirectory(local))
         return tree.failText(req.tag, E.NOENT, std.fmt.bufPrint(&p.fs.ename, "pager: {s}: no such directory", .{dir[0..@min(dir.len, 256)]}) catch "pager: no such directory");
-    p.fs.results_len = 0;
     const id = pardes.panes.Output.openPager(p, p.active, dir) catch |err|
         return tree.failText(req.tag, if (err == error.NoPaneRoom or err == error.NoPaneSlots) E.NOSPC else E.IO, switch (err) {
             error.NoPaneRoom, error.NoPaneSlots => "pager: no space for a +Pager pane",
@@ -4045,6 +4046,9 @@ test "pager answers its +Pager on the open that asked, whatever another client e
     // `pardes -` once read, and wrote its text into.
     try testing.expect(!std.mem.eql(u8, want, rd(p, exec, 0, 64).bytes));
     try testing.expectEqualStrings(want, call(p, .{ .tag = 5, .op = .read, .node = pager, .handle = asked, .size = 64 }).bytes);
+    // Refused, the same open answers nothing, not its last answer.
+    try testing.expectEqual(E.INVAL, call(p, .{ .tag = 6, .op = .write, .node = pager, .handle = asked, .data = "relative\n" }).errno());
+    try testing.expectEqualStrings("", call(p, .{ .tag = 7, .op = .read, .node = pager, .handle = asked, .size = 64 }).bytes);
     // One directory a write, absolute, and there.
     try testing.expectEqual(E.INVAL, wr(p, pager, "/a\n/b\n").errno());
     const relative = wr(p, pager, "relative\n");