An event record written back without its trailing newline is taken, as every other line file's last line is

`printf 'MX0 10' > event` was refused as a malformed record, while exec,
look and every ctl take a last line with no newline. The event file now
does too: a write not ending in a newline is read as though it did, and
the write still counts the bytes that came.

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

1 files changed, 19 insertions, 4 deletions

diff --git a/src/ninep/events.zig b/src/ninep/events.zig
index c6505f52..63405781 100644
--- a/src/ninep/events.zig
+++ b/src/ninep/events.zig
@@ -688,8 +688,17 @@ fn scanNumber(data: []const u8, i: *usize) ?u32 {
 }
 
 /// Writing a Look or Exec record back performs the action it names.
-pub fn writeEvent(p: *Pardes, req: Req, id: usize) Reply {
-    const pane0 = p.panes[id] orelse return Reply.fail(req.tag, E.NOENT);
+pub fn writeEvent(p: *Pardes, asked: Req, id: usize) Reply {
+    const pane0 = p.panes[id] orelse return Reply.fail(asked.tag, E.NOENT);
+    // Its last record needs no newline, as every other line file's last
+    // line does not (`printf 'MX0 10' > event`).
+    var req = asked;
+    if (req.data.len > 0 and req.data[req.data.len - 1] != '\n') {
+        const whole = p.scratch.allocator().alloc(u8, req.data.len + 1) catch return Reply.fail(req.tag, E.NOMEM);
+        @memcpy(whole[0..req.data.len], req.data);
+        whole[req.data.len] = '\n';
+        req.data = whole;
+    }
     const serial = pane0.serial;
     {
         const body = pane_files.bodyOf(pane0);
@@ -783,7 +792,7 @@ pub fn writeEvent(p: *Pardes, req: Req, id: usize) Reply {
             else => unreachable,
         }
     }
-    return .{ .tag = req.tag, .written = @intCast(req.data.len) };
+    return .{ .tag = req.tag, .written = @intCast(asked.data.len) };
 }
 
 // ---- tests ----
@@ -984,11 +993,17 @@ test "writing an event record back performs the action it names" {
     try testing.expectEqual(Status.ok, wr(p, event, "FX0 10\nFX0 10\n").reply.status);
     try testing.expectEqualStrings("fs-ran", pane.msg[0..pane.msg_len]);
 
+    // The last record needs no newline, as any line file's last line.
+    pane.msg_len = 0;
+    const bare = wr(p, event, "FX0 10");
+    try testing.expectEqual(Status.ok, bare.reply.status);
+    try testing.expectEqual(@as(u32, 6), bare.reply.written);
+    try testing.expectEqualStrings("fs-ran", pane.msg[0..pane.msg_len]);
+
     pane.msg_len = 0;
     for ([_][]const u8{
         "FX0 10\nFQ0 1\n", // unknown type character
         "FX0 999\n", // out of range
-        "FX0 10", // no newline
         "FX5 1\n", // q0 > q1
         "FD0 3\n", // a report, not a request
         "F\n",