A ctl write fails when a builtin it runs fails, and a missing required argument is refused before anything runs

A ctl write failed only on a malformed line: Mount x reported its error
in the editor while the write succeeded, and a bare Mount failed only as
it ran, after earlier lines of the write. acme's ctl answers a command's
error (editors/acme/xfid.c:700). Builtins now declare requires_arg beside
takes_arg (settings: those with a value to set), and the check refuses a
bare one as wrong #args before any line runs; while a ctl runs, the first
error a builtin reports fails the write, quoted with its line, and the
prompt refusal quotes its line too. Docs say what a failure mid-write
leaves done.

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

1 files changed, 6 insertions, 0 deletions

diff --git a/src/Messages.zig b/src/Messages.zig
index c7ff09be..f4ea1c3e 100644
--- a/src/Messages.zig
+++ b/src/Messages.zig
@@ -388,6 +388,12 @@ pub fn messageLog(m: *const Messages, i: usize) ?*const LoggedMessage {
 pub fn reportError(p: *Pardes, id: usize, operation: []const u8, err: anyerror) void {
     var buf: [256]u8 = undefined;
     const text = std.fmt.bufPrint(&buf, "{s}: {s}", .{ operation, @errorName(err) }) catch operation;
+    // A builtin a ctl write runs: its first error is also the write's.
+    if (p.fs.no_prompt and p.fs.failure_len == 0) {
+        const n = @min(text.len, p.fs.failure.len);
+        @memcpy(p.fs.failure[0..n], text[0..n]);
+        p.fs.failure_len = @intCast(n);
+    }
     setMessage(p, id, text);
 }