fix(completion): check that healthcheck name is string (#28458)

2 files changed, 16 insertions, 1 deletions

diff --git a/src/nvim/cmdexpand.c b/src/nvim/cmdexpand.c
index c1d219c32f..49944aa895 100644
--- a/src/nvim/cmdexpand.c
+++ b/src/nvim/cmdexpand.c
@@ -2598,7 +2598,8 @@ static char *get_healthcheck_names(expand_T *xp FUNC_ATTR_UNUSED, int idx)
     last_gen = get_cmdline_last_prompt_id();
   }
 
-  if (names.type == kObjectTypeArray && idx < (int)names.data.array.size) {
+  if (names.type == kObjectTypeArray && idx < (int)names.data.array.size
+      && names.data.array.items[idx].type == kObjectTypeString) {
     return names.data.array.items[idx].data.string.data;
   }
   return NULL;
diff --git a/test/functional/plugin/health_spec.lua b/test/functional/plugin/health_spec.lua
index 529d182603..9c17e74e19 100644
--- a/test/functional/plugin/health_spec.lua
+++ b/test/functional/plugin/health_spec.lua
@@ -6,6 +6,8 @@ local curbuf_contents = t.curbuf_contents
 local command = t.command
 local eq, neq, matches = t.eq, t.neq, t.matches
 local getcompletion = t.fn.getcompletion
+local exec_lua = t.exec_lua
+local assert_alive = t.assert_alive
 local insert = t.insert
 local source = t.source
 local fn = t.fn
@@ -20,6 +22,7 @@ describe(':checkhealth', function()
     eq(false, status)
     eq('Invalid $VIMRUNTIME: bogus', string.match(err, 'Invalid.*'))
   end)
+
   it("detects invalid 'runtimepath'", function()
     clear()
     command('set runtimepath=bogus')
@@ -27,6 +30,7 @@ describe(':checkhealth', function()
     eq(false, status)
     eq("Invalid 'runtimepath'", string.match(err, 'Invalid.*'))
   end)
+
   it('detects invalid $VIM', function()
     clear()
     -- Do this after startup, otherwise it just breaks $VIMRUNTIME.
@@ -34,6 +38,7 @@ describe(':checkhealth', function()
     command('checkhealth nvim')
     matches('ERROR $VIM .* zub', curbuf_contents())
   end)
+
   it('completions can be listed via getcompletion()', function()
     clear()
     eq('nvim', getcompletion('nvim', 'checkhealth')[1])
@@ -41,6 +46,15 @@ describe(':checkhealth', function()
     eq('vim.lsp', getcompletion('vim.ls', 'checkhealth')[1])
     neq('vim', getcompletion('^vim', 'checkhealth')[1]) -- should not complete vim.health
   end)
+
+  it('completion checks for vim.health._complete() return type #28456', function()
+    clear()
+    exec_lua([[vim.health._complete = function() return 1 end]])
+    eq({}, getcompletion('', 'checkhealth'))
+    exec_lua([[vim.health._complete = function() return { 1 } end]])
+    eq({}, getcompletion('', 'checkhealth'))
+    assert_alive()
+  end)
 end)
 
 describe('health.vim', function()