Joincol with no column to the right and Theme with no such theme say so

Both did nothing without a word, from a click or a ctl write alike, and a
script could not tell a no-op from success. Joincol in the rightmost column
now fails 'Joincol: no column to the right'. A Theme name that is none says so
and names the themes sharing its first letter, since all of them (ThemeSel
lists them) are too many for a message or a refused write; a startup config
line still fails quietly, as its other bad lines do.

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

1 files changed, 28 insertions, 2 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index 386fd9a9..1ba78457 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -213,7 +213,12 @@ fn checkBuiltin(p: *Pardes, req: Req, line: []const u8, scope: builtins.Scope) ?
     const takes = switch (setting.action) {
         .theme => for (pardes.themes) |t| {
             if (std.mem.eql(u8, t.name, arg)) break true;
-        } else false,
+        } else {
+            // `refuse` quotes the line after it, in what is left of 128.
+            var near: [40]u8 = undefined;
+            var why: [104]u8 = undefined;
+            return refuse(p, req, std.fmt.bufPrint(&why, "bad value in control message; like it: {s}; ThemeSel lists all", .{pardes.colors.themesNear(&near, arg)}) catch "bad value in control message", line);
+        },
         .font => config.Runtime.FontSpec.parse(arg) != null,
         else => probe: {
             var probe = p.settings;
@@ -638,7 +643,9 @@ test "the root ctl reads the settings as a write takes them, and takes the sessi
     try testing.expectEqualStrings("not a session control message \"Del\"", wr(p, root_ctl, "Del").reply.ename);
     try testing.expectEqualStrings("unknown control message \"Nonsense 1\"", wr(p, root_ctl, "Nonsense 1").reply.ename);
     try testing.expectEqualStrings("bad value in control message \"Verbose maybe\"", wr(p, root_ctl, "Verbose maybe").reply.ename);
-    try testing.expectEqualStrings("bad value in control message \"Theme no-such-theme\"", wr(p, root_ctl, "Theme no-such-theme").reply.ename);
+    const no_theme = wr(p, root_ctl, "Theme no-such-theme").reply.ename;
+    try testing.expectStringStartsWith(no_theme, "bad value in control message; like it: n");
+    try testing.expect(std.mem.endsWith(u8, no_theme, "; ThemeSel lists all \"Theme no-such-theme\""));
     try testing.expectEqualStrings("wrong #args in control message \"Newcol 2\"", wr(p, root_ctl, "Newcol 2").reply.ename);
     try testing.expectEqualStrings("wrong #args in control message \"Theme\"", wr(p, root_ctl, "Theme").reply.ename);
     // A bare required word fails the check, so the line before never runs.
@@ -951,3 +958,22 @@ test "an error's words give the errno a mount reads: EINVAL for what is malforme
         for (other) |w| try testing.expect(std.ascii.findIgnoreCase(c.text, w) == null);
     }
 }
+
+test "Joincol with no column to the right and Theme with no such theme say so" {
+    const gpa = testing.allocator;
+    const p = try withFile(gpa, "x\n");
+    defer p.deinit();
+    const root_ctl = @intFromEnum(tree.TopFile.ctl);
+    const joined = wr(p, root_ctl, "Joincol\n");
+    try testing.expectEqual(tree.Status.err, joined.reply.status);
+    try testing.expectStringStartsWith(joined.reply.ename, "Joincol: no column to the right");
+    const themed = wr(p, root_ctl, "Theme drak\n");
+    try testing.expectEqual(E.INVAL, themed.errno());
+    try testing.expectStringStartsWith(themed.reply.ename, "bad value in control message; like it: ");
+    try testing.expect(std.mem.indexOf(u8, themed.reply.ename, " dark") != null or std.mem.indexOf(u8, themed.reply.ename, ": dark") != null);
+    try testing.expect(std.mem.endsWith(u8, themed.reply.ename, "\"Theme drak\""));
+    // A click on the word says it on the message row.
+    _ = wr(p, Node.of(serialOf(p), .exec), "Theme drak\n");
+    const pane = p.panes[p.active].?;
+    try testing.expect(std.mem.indexOf(u8, pane.msg[0..pane.msg_len], "no theme \"drak\"") != null);
+}