fix(eval): skip over v:lua properly (#27517)

Problem:  Error when parsing v:lua in a ternary expression.
Solution: Set rettv->v_type for v:lua even if not evaluating.

3 files changed, 15 insertions, 2 deletions

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 4734e46362..3d224bfa0f 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -3238,6 +3238,13 @@ static int eval7(char **arg, typval_T *rettv, evalarg_T *const evalarg, bool wan
       } else {
         // skip the name
         check_vars(s, (size_t)len);
+        // If evaluate is false rettv->v_type was not set, but it's needed
+        // in handle_subscript() to parse v:lua, so set it here.
+        if (rettv->v_type == VAR_UNKNOWN && !evaluate && strnequal(s, "v:lua.", 6)) {
+          rettv->v_type = VAR_PARTIAL;
+          rettv->vval.v_partial = vvlua_partial;
+          rettv->vval.v_partial->pt_refcount++;
+        }
         ret = OK;
       }
     }
@@ -3442,7 +3449,7 @@ static int eval_method(char **const arg, typval_T *const rettv, evalarg_T *const
   int len;
   char *name = *arg;
   char *lua_funcname = NULL;
-  if (strncmp(name, "v:lua.", 6) == 0) {
+  if (strnequal(name, "v:lua.", 6)) {
     lua_funcname = name + 6;
     *arg = (char *)skip_luafunc_name(lua_funcname);
     *arg = skipwhite(*arg);  // to detect trailing whitespace later
@@ -7614,6 +7621,10 @@ int handle_subscript(const char **const arg, typval_T *rettv, evalarg_T *const e
   const char *lua_funcname = NULL;
 
   if (tv_is_luafunc(rettv)) {
+    if (!evaluate) {
+      tv_clear(rettv);
+    }
+
     if (**arg != '.') {
       tv_clear(rettv);
       ret = FAIL;
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 28365e16df..8dbff8a7a6 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -1726,7 +1726,7 @@ static void f_exists(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
       n = false;  // Trailing garbage.
     }
   } else if (*p == '*') {  // Internal or user defined function.
-    n = strncmp(p, "*v:lua.", 7) == 0 ? nlua_func_exists(p + 7) : function_exists(p + 1, false);
+    n = strnequal(p, "*v:lua.", 7) ? nlua_func_exists(p + 7) : function_exists(p + 1, false);
   } else if (*p == ':') {
     n = cmd_exists(p + 1);
   } else if (*p == '#') {
diff --git a/test/functional/lua/luaeval_spec.lua b/test/functional/lua/luaeval_spec.lua
index 171d37ba55..b28cfa4dd2 100644
--- a/test/functional/lua/luaeval_spec.lua
+++ b/test/functional/lua/luaeval_spec.lua
@@ -538,6 +538,8 @@ describe('v:lua', function()
     eq('\tbadval', eval("v:lua.require'leftpad'('badval')"))
     eq(9003, eval("v:lua.require'bar'.doit()"))
     eq(9004, eval("v:lua.require'baz-quux'.doit()"))
+    eq(9003, eval("1 ? v:lua.require'bar'.doit() : v:lua.require'baz-quux'.doit()"))
+    eq(9004, eval("0 ? v:lua.require'bar'.doit() : v:lua.require'baz-quux'.doit()"))
   end)
 
   it('throw errors for invalid use', function()