fix(api): return both link and attributes with nvim_get_hl (#22824)

Problem: No way to get the actual highlight attributes for a linked
group through |nvim_get_hl()| (not the attributes from the link target).
Solution: Return the actual attributes as well as the link target name.

2 files changed, 17 insertions, 14 deletions

diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index ca5dd97020..9812313b7b 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -95,6 +95,9 @@ Integer nvim_get_hl_id_by_name(String name)
 /// @param[out] err Error details, if any.
 /// @return Highlight groups as a map from group name to a highlight definition map as in |nvim_set_hl()|,
 ///                   or only a single highlight definition map if requested by name or id.
+///
+/// @note When the `link` attribute is defined in the highlight definition
+///       map, other attributes will not be taking effect (see |:hi-link|).
 Dictionary nvim_get_hl(Integer ns_id, Dict(get_highlight) *opts, Arena *arena, Error *err)
   FUNC_API_SINCE(11)
 {
@@ -113,6 +116,10 @@ Dictionary nvim_get_hl(Integer ns_id, Dict(get_highlight) *opts, Arena *arena, E
 ///       values of the Normal group. If the Normal group has not been defined,
 ///       using these values results in an error.
 ///
+///
+/// @note If `link` is used in combination with other attributes; only the
+///       `link` will take effect (see |:hi-link|).
+///
 /// @param ns_id Namespace id for this highlight |nvim_create_namespace()|.
 ///              Use 0 to set a highlight group globally |:highlight|.
 ///              Highlights from non-global namespaces are not active by default, use
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index 057447c9f4..56fa206247 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -797,9 +797,9 @@ void set_hl_group(int id, HlAttrs attrs, Dict(highlight) *dict, int link_id)
   }
 
   HlGroup *g = &hl_table[idx];
+  g->sg_cleared = false;
 
   if (link_id > 0) {
-    g->sg_cleared = false;
     g->sg_link = link_id;
     g->sg_script_ctx = current_sctx;
     g->sg_script_ctx.sc_lnum += SOURCING_LNUM;
@@ -809,11 +809,10 @@ void set_hl_group(int id, HlAttrs attrs, Dict(highlight) *dict, int link_id)
       g->sg_deflink_sctx = current_sctx;
       g->sg_deflink_sctx.sc_lnum += SOURCING_LNUM;
     }
-    goto update;
+  } else {
+    g->sg_link = 0;
   }
 
-  g->sg_cleared = false;
-  g->sg_link = 0;
   g->sg_gui = attrs.rgb_ae_attr;
 
   g->sg_rgb_fg = attrs.rgb_fg_color;
@@ -865,7 +864,6 @@ void set_hl_group(int id, HlAttrs attrs, Dict(highlight) *dict, int link_id)
     }
   }
 
-update:
   if (!updating_screen) {
     redraw_all_later(UPD_NOT_VALID);
   }
@@ -1533,17 +1531,15 @@ static bool hlgroup2dict(Dictionary *hl, NS ns_id, int hl_id, Arena *arena)
   }
   HlAttrs attr =
     syn_attr2entry(ns_id == 0 ? sgp->sg_attr : ns_get_hl(&ns_id, hl_id, false, sgp->sg_set));
+  *hl = arena_dict(arena, HLATTRS_DICT_SIZE + 1);
   if (link > 0) {
-    *hl = arena_dict(arena, 1);
     PUT_C(*hl, "link", STRING_OBJ(cstr_as_string(hl_table[link - 1].sg_name)));
-  } else {
-    *hl = arena_dict(arena, HLATTRS_DICT_SIZE);
-    Dictionary hl_cterm = arena_dict(arena, HLATTRS_DICT_SIZE);
-    hlattrs2dict(hl, NULL, attr, true, true);
-    hlattrs2dict(hl, &hl_cterm, attr, false, true);
-    if (kv_size(hl_cterm)) {
-      PUT_C(*hl, "cterm", DICTIONARY_OBJ(hl_cterm));
-    }
+  }
+  Dictionary hl_cterm = arena_dict(arena, HLATTRS_DICT_SIZE);
+  hlattrs2dict(hl, NULL, attr, true, true);
+  hlattrs2dict(hl, &hl_cterm, attr, false, true);
+  if (kv_size(hl_cterm)) {
+    PUT_C(*hl, "cterm", DICTIONARY_OBJ(hl_cterm));
   }
   return true;
 }