A ThemeFile that cannot be read or is no theme fails its write, and a bad path says why

The theme is read when the host performs the request, after the write had been answered, so a missing file or a bad theme only showed a message; and a path not ending .zon said only invalid theme path. Load failures are now the waiting write's (late, as a Save's), and the path refusal says a theme file is a .zon.

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

1 files changed, 8 insertions, 4 deletions

diff --git a/src/builtins.zig b/src/builtins.zig
index ca01e0fe..ec6afeae 100644
--- a/src/builtins.zig
+++ b/src/builtins.zig
@@ -808,10 +808,14 @@ pub const ThemeFile = struct {
     pub const requires_arg = true;
     pub const enabled = pardes.hosted;
     pub fn run(c: Ctx) void {
-        if (comptime enabled)
-            colors.requestThemeFile(c.p, c.id, c.arg orelse return)
-        else
-            unreachable;
+        if (comptime !enabled) unreachable;
+        const arg = std.mem.trim(u8, c.arg orelse return, " \t\r\n");
+        // Said with why, not "invalid theme path".
+        if (!std.mem.endsWith(u8, arg, ".zon")) {
+            var said: [320]u8 = undefined;
+            return c.p.reportFailure(c.id, std.fmt.bufPrint(&said, "ThemeFile: {s}: invalid theme path: a theme file is a .zon (DumpThemes writes some to start from)", .{arg[0..@min(arg.len, 200)]}) catch "ThemeFile: invalid theme path: a theme file is a .zon");
+        }
+        colors.requestThemeFile(c.p, c.id, arg);
     }
 };