fix(api): nvim_set_hl bail out on invalid group name (#20021)

2 files changed, 11 insertions, 4 deletions

diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index b164106cef..a1721d433f 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -86,8 +86,7 @@ Dictionary nvim_get_hl_by_name(String name, Boolean rgb, Error *err)
   int id = syn_name2id(name.data);
 
   if (id == 0) {
-    api_set_error(err, kErrorTypeException, "Invalid highlight name: %s",
-                  name.data);
+    api_set_error(err, kErrorTypeException, "Invalid highlight name: %s", name.data);
     return result;
   }
   result = nvim_get_hl_by_id(id, rgb, err);
@@ -105,8 +104,7 @@ Dictionary nvim_get_hl_by_id(Integer hl_id, Boolean rgb, Error *err)
 {
   Dictionary dic = ARRAY_DICT_INIT;
   if (syn_get_final_id((int)hl_id) == 0) {
-    api_set_error(err, kErrorTypeException,
-                  "Invalid highlight id: %" PRId64, hl_id);
+    api_set_error(err, kErrorTypeException, "Invalid highlight id: %" PRId64, hl_id);
     return dic;
   }
   int attrcode = syn_id2attr((int)hl_id);
@@ -175,6 +173,10 @@ void nvim_set_hl(Integer ns_id, String name, Dict(highlight) *val, Error *err)
   FUNC_API_SINCE(7)
 {
   int hl_id = syn_check_group(name.data, name.size);
+  if (hl_id == 0) {
+    api_set_error(err, kErrorTypeException, "Invalid highlight name: %s", name.data);
+    return;
+  }
   int link_id = -1;
 
   HlAttrs attrs = dict2hlattrs(val, true, &link_id, err);
diff --git a/test/functional/api/highlight_spec.lua b/test/functional/api/highlight_spec.lua
index 2730f7e23d..3b36563d21 100644
--- a/test/functional/api/highlight_spec.lua
+++ b/test/functional/api/highlight_spec.lua
@@ -354,4 +354,9 @@ describe("API: set highlight", function()
     meths.set_hl(0, 'Normal', {fg='#000083', bg='#0000F3'})
     eq({foreground = 131, background = 243}, nvim("get_hl_by_name", 'Normal', true))
   end)
+
+  it('does not segfault on invalid group name #20009', function()
+    eq('Invalid highlight name: foo bar', pcall_err(meths.set_hl, 0, 'foo bar', {bold = true}))
+    assert_alive()
+  end)
 end)