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, 5 insertions, 1 deletions

diff --git a/src/fs.zig b/src/fs.zig
index 339910a4..022a326a 100644
--- a/src/fs.zig
+++ b/src/fs.zig
@@ -1257,9 +1257,13 @@ pub const Namespace = struct {
     listeners: u16 = 0,
     origin: u8 = 'K',
     /// A ctl write is running builtins: one that would open a prompt for
-    /// its argument refuses (`refused`), since nobody is at the prompt.
+    /// its argument refuses (`refused`), since nobody is at the prompt, and
+    /// the first error one reports (`failure`) fails the write, as acme's
+    /// ctl answers a command's error (editors/acme/xfid.c:700).
     no_prompt: bool = false,
     refused: bool = false,
+    failure: [96]u8 = undefined,
+    failure_len: u8 = 0,
     /// A refusal that quotes the message it refuses, as Plan 9's cmderror
     /// does (kernel/misc/parse.c:82); answered at once (src/9p_io.zig).
     ename: [128]u8 = undefined,