Errors are said in words, and a refusal names what it takes

A failure read `Del k|j: InvalidArgument`, `Kill: NoSuchCommand`, `ill-formed control message`, or nothing at all. reportError now spells an error's name as words, and the refusals name their accepted forms: pty/ctl lists its verbs, a flag file takes 1 or 0, a setting word takes on or off, Del takes k, j or nothing, Repl takes - or a language. Kill with nothing to stop says so, /focus says pane, a Look that found nothing says no match, and pty/run on a command pane says it is not a shell. A ctl write's failure has room for the Repl list and is cut between words, the Repl word at a character.

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

4 files changed, 34 insertions, 8 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index 4e1c039b..680a09b0 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -200,7 +200,7 @@ const Builtin = builtins.registry.Builtin();
 /// Refuses a control message, quoting it the way Plan 9's cmderror does
 /// (kernel/misc/parse.c:82): `unknown control message "Bogus 3"`.
 fn refuse(p: *Pardes, req: Req, why: []const u8, line: []const u8) Reply {
-    const room = p.fs.ename.len - why.len - 3;
+    const room = p.fs.ename.len -| (why.len + 3);
     const text = std.fmt.bufPrint(&p.fs.ename, "{s} \"{s}\"", .{ why, line[0..@min(line.len, room)] }) catch why;
     return tree.failText(req.tag, E.INVAL, text);
 }
@@ -399,7 +399,7 @@ pub fn writeFocus(p: *Pardes, req: Req) Reply {
     return .{ .tag = req.tag, .written = @intCast(req.data.len) };
 }
 
-const e_no_pane = "no such window";
+const e_no_pane = "no such pane";
 
 pub fn readPane(p: *Pardes, req: Req, pane: *Pane) Reply {
     var buf: [pane_text_cap]u8 = undefined;
@@ -666,7 +666,7 @@ test "the root ctl reads the settings as a write takes them, and takes the sessi
     // its line; the lines before it have taken effect, as in acme.
     const failed = wr(p, root_ctl, "Verbose on\nMount x\nVerbose off");
     try testing.expectEqual(E.IO, failed.errno());
-    try testing.expectEqualStrings("Mount name dial: MissingArgument \"Mount x\"", failed.reply.ename);
+    try testing.expectEqualStrings("Mount name dial: missing argument \"Mount x\"", failed.reply.ename);
     try testing.expect(p.settings.verbose);
     try testing.expect(!p.fs.no_prompt);
     try testing.expectEqual(Status.ok, wr(p, root_ctl, "Verbose off").reply.status);
diff --git a/src/ninep/events.zig b/src/ninep/events.zig
index cff42c55..ffdea95b 100644
--- a/src/ninep/events.zig
+++ b/src/ninep/events.zig
@@ -877,7 +877,7 @@ test "a refused or failed write is an err record in the log, saying which file a
     _ = wr(p, @intFromEnum(tree.TopFile.ctl), "Bogus");
     try testing.expectEqualStrings("err - ctl: unknown control message \"Bogus\"\n", next.record(p, f, frozen));
     _ = wr(p, @intFromEnum(tree.TopFile.focus), "99999");
-    try testing.expectEqualStrings("err - focus: no such window\n", next.record(p, f, frozen));
+    try testing.expectEqualStrings("err - focus: no such pane\n", next.record(p, f, frozen));
     // A write that succeeds says nothing.
     _ = wr(p, Node.of(serial, .addr), "#0");
     try testing.expectEqual(Status.again, call(p, .{ .tag = 5, .op = .read, .node = log, .handle = f, .off = frozen, .size = 4096 }).reply.status);
diff --git a/src/ninep/pane.zig b/src/ninep/pane.zig
index 77be80c6..d2b2a791 100644
--- a/src/ninep/pane.zig
+++ b/src/ninep/pane.zig
@@ -507,7 +507,7 @@ fn writeRange(req: Req, pane: *Pane, file: PaneFile) Reply {
 
 fn writeFlag(p: *Pardes, req: Req, pane: *Pane, file: PaneFile) Reply {
     const word = std.mem.trim(u8, req.data, " \t\r\n");
-    if (!std.mem.eql(u8, word, "1") and !std.mem.eql(u8, word, "0")) return Reply.fail(req.tag, E.INVAL);
+    if (!std.mem.eql(u8, word, "1") and !std.mem.eql(u8, word, "0")) return tree.failText(req.tag, E.INVAL, "takes 1 or 0");
     const on = word[0] == '1';
     const pf = &pane.fs;
     switch (file) {
@@ -873,8 +873,10 @@ test "the flag files read and write the state acme kept behind ctl verbs" {
 
     for ([_]u64{ dirty, mark, scroll }) |node| {
         try testing.expectEqual(@as(u64, 2), call(p, .{ .tag = 1, .op = .getattr, .node = node }).reply.attr.size);
-        for ([_][]const u8{ "", "yes", "2", "0 1", "true" }) |bad|
+        for ([_][]const u8{ "", "yes", "2", "0 1", "true" }) |bad| {
             try testing.expectEqual(E.INVAL, wr(p, node, bad).errno());
+            try testing.expectEqualStrings("takes 1 or 0", wr(p, node, bad).reply.ename);
+        }
     }
 
     try testing.expectEqualStrings("0\n", rd(p, dirty, 0, 8).bytes);
diff --git a/src/ninep/pty.zig b/src/ninep/pty.zig
index 88dafdfc..a2a40811 100644
--- a/src/ninep/pty.zig
+++ b/src/ninep/pty.zig
@@ -43,7 +43,7 @@ pub fn writeCtl(p: *Pardes, req: Req, id: usize) Reply {
         while (it.next()) |raw| {
             const line = std.mem.trim(u8, raw, " \t\r");
             if (line.len == 0) continue;
-            if (!verb(p, id, line, apply)) return tree.failText(req.tag, E.INVAL, tree.e_bad_ctl);
+            if (!verb(p, id, line, apply)) return tree.failText(req.tag, E.INVAL, e_bad_pty_ctl);
         }
     }
     return .{ .tag = req.tag, .written = @intCast(req.data.len) };
@@ -165,7 +165,10 @@ pub fn writeRun(p: *Pardes, req: Req, id: usize, pane: *Pane) Reply {
     const pf = &pane.fs;
     const state = pane.terminal orelse return tree.failText(req.tag, E.INVAL, e_bad_line);
     const marks = &state.stream.handler;
-    if (pf.unmarked) {
+    if (pane.command != null) {
+        // Its child is the command, and no shell is there to take a line.
+        answer(p, slot, "error {s}", .{if (pane.command_done) "command done; not a shell" else "a command runs here, not a shell"});
+    } else if (pf.unmarked) {
         answer(p, slot, "error no prompt marks", .{});
     } else if (waitingRun(p, pane) != null or (marks.prompts > 0 and (marks.phase != .input or
         !pardes.panes.Terminal.promptInputEmpty(pane) or p.hostTtyTaken(id))))
@@ -335,6 +338,7 @@ fn waitingRun(p: *Pardes, pane: *Pane) ?*Run {
 }
 
 const e_bad_line = "bad command line";
+const e_bad_pty_ctl = tree.e_bad_ctl ++ "; takes winsize COLS ROWS, sig INT|TERM|HUP|QUIT|KILL, or exec";
 
 pub fn readData(p: *Pardes, req: Req, pf: *pane_files.State) Reply {
     if (pf.pty_out.empty()) return .{ .tag = req.tag, .status = .again };
@@ -505,6 +509,7 @@ test "every pty/ctl verb, and every refusal" {
     }) |bad| {
         const a = wr(p, ctl, bad);
         try testing.expectEqual(E.INVAL, a.errno());
+        try testing.expectEqualStrings(e_bad_pty_ctl, a.reply.ename); // names what it takes
         try testing.expect(a.winsize == null);
         try testing.expect(a.signal == null);
         try testing.expect(!a.spawned);
@@ -743,6 +748,25 @@ test "run answers how its command ended once the shell is back at a prompt" {
     for (p.fs.opens) |o| try testing.expect(o.node == 0);
 }
 
+test "run on a command pane says no shell is there" {
+    const gpa = testing.allocator;
+    const p = try withTerm(gpa);
+    defer p.deinit();
+    const node = Node.of(serialOf(p), .pty_run);
+    const pane = p.panes[0].?;
+    pane.command = try gpa.dupe(u8, "make");
+    for ([_]struct { bool, []const u8 }{
+        .{ false, "error a command runs here, not a shell\n" },
+        .{ true, "error command done; not a shell\n" },
+    }) |case| {
+        pane.command_done = case[0];
+        const o = call(p, .{ .tag = 1, .op = .open, .node = node });
+        _ = call(p, .{ .tag = 2, .op = .write, .node = node, .handle = o.reply.handle, .data = "ls\n" });
+        try testing.expectEqualStrings(case[1], call(p, .{ .tag = 3, .op = .read, .node = node, .handle = o.reply.handle, .size = 64 }).bytes);
+        _ = call(p, .{ .tag = 4, .op = .release, .node = node, .handle = o.reply.handle });
+    }
+}
+
 test "a run's answer says cut when its output's start is gone, and reads a bounded tail" {
     const gpa = testing.allocator;
     const p = try withTerm(gpa);