Errnos that fit: a Dump into a missing DumpDir and a shell that is not there are ENOENT, a GUI-only setting EINVAL

A Dump into a DumpDir not there failed EIO `file not found`; `no shell
"x"` read as EIO through a mount; and a GUI-only setting on a terminal,
EINVAL in the reply, had no word 9ns reads as EINVAL. Each says so in the
words that give its errno: `no such directory`, `not found`, `invalid
here`.

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

1 files changed, 6 insertions, 4 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index 5f26a181..a474c781 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -386,7 +386,9 @@ fn checkBuiltin(p: *Pardes, req: Req, line: []const u8, scope: builtins.Scope) ?
         // terminal) is known, and says so rather than sound misspelt.
         if (config.Runtime.find(word) != null) {
             var why: [64]u8 = undefined;
-            return refuse(p, req, std.fmt.bufPrint(&why, "{s} is GUI-only", .{word}) catch "GUI-only", line);
+            // EINVAL, a request this build cannot take, in words 9ns reads
+            // as that: `invalid`.
+            return refuse(p, req, std.fmt.bufPrint(&why, "{s} is GUI-only, invalid here", .{word}) catch "GUI-only, invalid here", line);
         }
         return refuse(p, req, "unknown control message", line);
     };
@@ -1653,7 +1655,7 @@ test "a Restore of a file that is no dump fails the write before any warning, an
 
     p.fs.late_failure_len = 0;
     p.dumpFailed("/nowhere/pardes.dump.zon", error.FileNotFound);
-    try testing.expectEqualStrings("Dump /nowhere/pardes.dump.zon: file not found", p.fs.late_failure[0..p.fs.late_failure_len]);
+    try testing.expectEqualStrings("Dump /nowhere/pardes.dump.zon: no such directory", p.fs.late_failure[0..p.fs.late_failure_len]);
 }
 
 test "a setting this frontend cannot show says GUI-only, and DumpDir reads back the directory in effect" {
@@ -1661,8 +1663,8 @@ test "a setting this frontend cannot show says GUI-only, and DumpDir reads back
     defer p.deinit();
     const root_ctl = @intFromEnum(tree.TopFile.ctl);
     if (!builtins.capabilities.lift) {
-        try testing.expectEqualStrings("Lift is GUI-only \"Lift on\"", wr(p, root_ctl, "Lift on\n").reply.ename);
-        try testing.expectEqualStrings("GripWidth is GUI-only \"GripWidth 120\"", wr(p, root_ctl, "GripWidth 120\n").reply.ename);
+        try testing.expectEqualStrings("Lift is GUI-only, invalid here \"Lift on\"", wr(p, root_ctl, "Lift on\n").reply.ename);
+        try testing.expectEqualStrings("GripWidth is GUI-only, invalid here \"GripWidth 120\"", wr(p, root_ctl, "GripWidth 120\n").reply.ename);
     }
     try testing.expectEqualStrings("unknown control message \"Liftt on\"", wr(p, root_ctl, "Liftt on\n").reply.ename);
     var buf: [900]u8 = undefined;