fix(v:lua): fix emsg when calling v:lua directly

seandewar · seandewar · commit da9005af792f · 2021-08-12T22:35:25.000+01:00
v:lua expressions are represented using vvlua_partial. As v:lua isn't
intended to be called directly, it's given an empty pt_name.

Because of this, calling v:lua directly like "v:lua()" will cause "E117:
Unknown function: ", with an empty name.

Instead, have call_func() show the name "v:lua" in the emsg.
diff --git a/src/nvim/eval/userfunc.c b/src/nvim/eval/userfunc.c
@@ -1516,6 +1516,10 @@ call_func(
       if (len > 0) {
         error = ERROR_NONE;
         nlua_typval_call((const char *)funcname, len, argvars, argcount, rettv);
+      } else {
+        // v:lua was called directly; show its name in the emsg
+        XFREE_CLEAR(name);
+        funcname = (const char_u *)"v:lua";
       }
     } else if (fp != NULL || !builtin_function((const char *)rfname, -1)) {
       // User defined function.
diff --git a/test/functional/lua/luaeval_spec.lua b/test/functional/lua/luaeval_spec.lua
@@ -518,6 +518,7 @@ describe('v:lua', function()
 
     eq("Vim:E15: Invalid expression: v:['lua'].foo()", pcall_err(eval, "v:['lua'].foo()"))
     eq("Vim(call):E461: Illegal variable name: v:['lua']", pcall_err(command, "call v:['lua'].baar()"))
+    eq("Vim:E117: Unknown function: v:lua", pcall_err(eval, "v:lua()"))
 
     eq("Vim(let):E46: Cannot change read-only variable \"v:['lua']\"", pcall_err(command, "let v:['lua'] = 'xx'"))
     eq("Vim(let):E46: Cannot change read-only variable \"v:lua\"", pcall_err(command, "let v:lua = 'xx'"))
