fix(hl): return cterm fg/bg even if they match Normal neovim#18981

Fixes neovim#18980

- 831fa45 is related but this doesn't regress that
- The `cterm_normal_fg_color != ae.cterm_fg_color` comparison is originally
  carried from patch to patch starting all the way back in 29bc6df where it
  was avoiding setting a HL attr. But `hlattrs2dict()` now is just
  informational.

src/nvim/highlight.c

@@ -794,11 +794,11 @@ Dictionary hlattrs2dict(HlAttrs ae, bool use_rgb)
       PUT(hl, "special", INTEGER_OBJ(ae.rgb_sp_color));
     }
   } else {
-    if (cterm_normal_fg_color != ae.cterm_fg_color && ae.cterm_fg_color != 0) {
+    if (ae.cterm_fg_color != 0) {
       PUT(hl, "foreground", INTEGER_OBJ(ae.cterm_fg_color - 1));
     }
 
-    if (cterm_normal_bg_color != ae.cterm_bg_color && ae.cterm_bg_color != 0) {
+    if (ae.cterm_bg_color != 0) {
       PUT(hl, "background", INTEGER_OBJ(ae.cterm_bg_color - 1));
     }
   }

test/functional/api/highlight_spec.lua

@@ -133,6 +133,13 @@ describe('API: highlight',function()
     eq({ underline = true, standout = true, },
        meths.get_hl_by_name('cursorline', 0));
 
+    -- Test cterm & Normal values. #18024 (tail) & #18980
+    -- Ensure Normal, and groups that match Normal return their fg & bg cterm values
+    meths.set_hl(0, 'Normal', {ctermfg = 17, ctermbg = 213})
+    meths.set_hl(0, 'NotNormal', {ctermfg = 17, ctermbg = 213})
+    -- Note colors are "cterm" values, not rgb-as-ints
+    eq({foreground = 17, background = 213}, nvim("get_hl_by_name", 'Normal', false))
+    eq({foreground = 17, background = 213}, nvim("get_hl_by_name", 'NotNormal', false))
   end)
 
   it('nvim_get_hl_id_by_name', function()