A builtin or setting this build lacks is refused GUI-only, from an exec too

On a terminal, Fonts written to an exec was no builtin there, so it ran as a shell command and ended exit 127; ctl said unknown control message. Both now say Fonts is GUI-only, invalid here (a builtin another platform's build has, not in this build).

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

1 files changed, 19 insertions, 0 deletions

diff --git a/src/builtins.zig b/src/builtins.zig
index 9025da6d..b0499dc0 100644
--- a/src/builtins.zig
+++ b/src/builtins.zig
@@ -56,6 +56,22 @@ fn isEnabled(comptime T: type) bool {
     return !@hasDecl(T, "enabled") or T.enabled;
 }
 
+/// Why `word`, a builtin some build has, is none in this one: `GUI-only`
+/// for the GUI's own (`gui_only`), else `not in this build`; null for a
+/// word that is one here, or in no build.
+pub fn absentWhy(name: []const u8) ?[]const u8 {
+    @setEvalBranchQuota(20000);
+    inline for (@typeInfo(@This()).@"struct".decls) |d| {
+        if (comptime @TypeOf(@field(@This(), d.name)) == type) {
+            const T = @field(@This(), d.name);
+            if (comptime @typeInfo(T) == .@"struct" and @hasDecl(T, "run") and !isEnabled(T)) {
+                if (std.mem.eql(u8, d.name, name)) return if (@hasDecl(T, "gui_only")) "GUI-only" else "not in this build";
+            }
+        }
+    }
+    return null;
+}
+
 fn manualBuiltinCount() comptime_int {
     comptime {
         var count = 0;
@@ -814,6 +830,7 @@ pub const Fonts = struct {
     pub const scope: Scope = .session;
     pub const output: OutputTraits = .{ .name = config.fonts_buffer, .steps = true, .commands = true };
     pub const enabled = capabilities.font_picker;
+    pub const gui_only = true;
     pub fn run(c: Ctx) void {
         if (comptime enabled) apply(c) else unreachable;
     }
@@ -1319,6 +1336,7 @@ pub const EffectCode = struct {
     pub const takes_arg = true;
     pub const requires_arg = true;
     pub const enabled = capabilities.panel_transitions or capabilities.scene_shaders;
+    pub const gui_only = true;
     pub const output: OutputTraits = .{ .name = config.effect_code_buffer };
     pub fn run(c: Ctx) void {
         if (comptime enabled)
@@ -1335,6 +1353,7 @@ pub const Pet = struct {
     pub const takes_arg = true;
     pub const requires_arg = true;
     pub const enabled = pardes.platform == .gui;
+    pub const gui_only = true;
     pub fn run(c: Ctx) void {
         const name = std.mem.trim(u8, c.arg orelse return, " \t\r\n");
         c.p.settings.pet = std.meta.stringToEnum(@TypeOf(c.p.settings.pet), name) orelse return;