fix(argon2) avoid getting config upvalue in largon2_verify and better

"too many arguments" error messages

spec/argon2_spec.lua

@@ -43,7 +43,7 @@ describe("encrypt()", function()
 
     assert.has_error(function()
       argon2.encrypt("", "", {}, "")
-    end, "bad argument #4 to 'encrypt' (found too many arguments)")
+    end, "expecting no more than 3 arguments, but got 4")
   end)
   it("salt too short", function()
     local hash, err = argon2.encrypt("password", "")
@@ -92,6 +92,10 @@ describe("verify()", function()
   it("should throw error on invalid argument", function()
     assert.has_error(function()
       argon2.verify(nil)
+    end, "expecting 2 arguments, but got 1")
+
+    assert.has_error(function()
+      argon2.verify(nil, nil)
     end, "bad argument #1 to 'verify' (string expected, got nil)")
 
     assert.has_error(function()
@@ -100,7 +104,7 @@ describe("verify()", function()
 
     assert.has_error(function()
       argon2.verify("", "", "")
-    end, "bad argument #3 to 'verify' (found too many arguments)")
+    end, "expecting 2 arguments, but got 3")
   end)
   it("should verify ok", function()
     local hash = assert(argon2.encrypt("password", "somesalt"))
@@ -128,15 +132,15 @@ describe("module settings", function()
   it("should throw error on invalid argument", function()
     assert.has_error(function()
       argon2.t_cost(0, 0)
-    end, "bad argument #2 to 't_cost' (found too many arguments)")
+    end, "expecting no more than 1 arguments, but got 2")
 
     assert.has_error(function()
       argon2.t_cost ""
     end, "bad argument #1 to 't_cost' (expected t_cost to be a number, got string)")
 
     assert.has_error(function()
-      argon2.argon2d(0, 0)
-    end, "bad argument #2 to 'argon2d' (found too many arguments)")
+      argon2.argon2d(0)
+    end, "bad argument #1 to 'argon2d' (invalid option '0')")
 
     assert.has_error(function()
       argon2.argon2d "idk"

src/argon2.c

@@ -91,11 +91,13 @@ largon2_fetch_config(lua_State *L)
 static largon2_config_t*
 largon2_arg_init(lua_State *L, int nargs)
 {
-    luaL_argcheck(L, lua_gettop(L) <= nargs, nargs + 1,
-                  "found too many arguments");
+    if (lua_gettop(L) > nargs) {
+        luaL_error(L, "expecting no more than %d arguments, but got %d",
+                   nargs, lua_gettop(L));
+        return NULL;
+    }
 
-    while (lua_gettop(L) < nargs)
-        lua_pushnil(L);
+    lua_settop(L, nargs);
 
     return largon2_fetch_config(L);
 }
@@ -305,7 +307,10 @@ largon2_verify(lua_State *L)
     size_t              plainlen;
     argon2_type         type;
 
-    largon2_arg_init(L, 2);
+    if (lua_gettop(L) != 2) {
+        return luaL_error(L, "expecting 2 arguments, but got %d",
+                          lua_gettop(L));
+    }
 
     encoded = luaL_checkstring(L, 1);
     plain   = luaL_checklstring(L, 2, &plainlen);