Every EINVAL a write gets says why; DEL in an exec or look line is a control character

An empty name, a word written to log other than follow, a data, sel, dot
or dirty write to a pane with no text, a truncate other than to zero,
and a control character in a look line written through a held open were
refused with no words, logged as `Invalid argument`. Each says its reason
now; and DEL is refused in exec and look lines as in names.

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

1 files changed, 1 insertions, 1 deletions

diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index ed0e0352..391847f5 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -1007,7 +1007,7 @@ fn write(p: *Pardes, req: Req, target: Target) Reply {
     if (o.what != .lines and o.what != .ctl) return writeNow(p, req, target);
     // A clicked line holds no control character: refused at once, not held
     // to fail unseen at the close.
-    if (resultsFile(target)) for (req.data) |c| if (c < ' ' and c != '\t' and c != '\n' and c != '\r') return Reply.fail(req.tag, E.INVAL);
+    if (resultsFile(target)) for (req.data) |c| if ((c < ' ' and c != '\t' and c != '\n' and c != '\r') or c == 0x7f) return failText(req.tag, E.INVAL, ctl.e_control);
     o.pending.appendSlice(p.gpa, req.data) catch return Reply.fail(req.tag, E.NOMEM);
     const end = ctl.completeEnd(p, o.pending.items);
     if (end == 0) {