fix(highlight): add force in nvim_set_hl

runtime/doc/api.txt

@@ -1458,6 +1458,8 @@ nvim_set_hl({ns_id}, {name}, {*val})                           *nvim_set_hl()*
                  • cterm: cterm attribute map, like |highlight-args|. If not
                    set, cterm attributes will match those from the attribute
                    map documented above.
+                 • force: if true force update the highlight group when it
+                   exists.
 
 nvim_set_hl_ns({ns_id})                                     *nvim_set_hl_ns()*
     Set active namespace for highlights defined with |nvim_set_hl()|. This can

runtime/lua/vim/_meta/api.lua

@@ -1857,6 +1857,8 @@ function vim.api.nvim_set_decoration_provider(ns_id, opts) end
 ---              • cterm: cterm attribute map, like `highlight-args`. If not
 ---                set, cterm attributes will match those from the attribute
 ---                map documented above.
+---              • force: if true force update the highlight group when it
+---                exists.
 function vim.api.nvim_set_hl(ns_id, name, val) end
 
 --- Set active namespace for highlights defined with `nvim_set_hl()`. This can

runtime/lua/vim/_meta/api_keysets.lua

@@ -164,6 +164,7 @@ error('Cannot require a meta file')
 --- @field blend? integer
 --- @field fg_indexed? boolean
 --- @field bg_indexed? boolean
+--- @field force? boolean
 
 --- @class vim.api.keyset.highlight_cterm
 --- @field bold? boolean

src/nvim/api/keysets.h

@@ -168,6 +168,7 @@ typedef struct {
   Integer blend;
   Boolean fg_indexed;
   Boolean bg_indexed;
+  Boolean force;
 } Dict(highlight);
 
 typedef struct {

src/nvim/api/vim.c

@@ -151,6 +151,7 @@ Dictionary nvim_get_hl(Integer ns_id, Dict(get_highlight) *opts, Arena *arena, E
 ///                - cterm: cterm attribute map, like |highlight-args|. If not set,
 ///                         cterm attributes will match those from the attribute map
 ///                         documented above.
+///                - force: if true force update the highlight group when it exists.
 /// @param[out] err Error details, if any
 ///
 // TODO(bfredl): val should take update vs reset flag

src/nvim/highlight_group.c

@@ -799,11 +799,10 @@ int lookup_color(const int idx, const bool foreground, TriState *const boldp)
 void set_hl_group(int id, HlAttrs attrs, Dict(highlight) *dict, int link_id)
 {
   int idx = id - 1;  // Index is ID minus one.
-
   bool is_default = attrs.rgb_ae_attr & HL_DEFAULT;
 
   // Return if "default" was used and the group already has settings
-  if (is_default && hl_has_settings(idx, true)) {
+  if (is_default && hl_has_settings(idx, true) && !dict->force) {
     return;
   }
 

test/functional/api/highlight_spec.lua

@@ -625,4 +625,15 @@ describe('API: get highlight', function()
     eq('FooBarA        xxx cterm=bold,italic guifg=#ffffff',
       exec_capture('highlight FooBarA'))
   end)
+
+  it('can override exist highlight group by force #20323', function()
+    local white = tonumber('ffffff', 16)
+    local green = tonumber('00ff00', 16)
+    meths.set_hl(0, 'Foo', { fg=white })
+    meths.set_hl(0, 'Foo', { fg=green, force = true })
+    eq({ fg = green },meths.get_hl(0, {name = 'Foo'}))
+    meths.set_hl(0, 'Bar', {link = 'Comment', default = true})
+    meths.set_hl(0, 'Bar', {link = 'Foo',default = true, force = true})
+    eq({link ='Foo', default = true}, meths.get_hl(0, {name = 'Bar'}))
+  end)
 end)