Fixup after enabling recursive variables validation

Author: Totktonada

graphql/convert_schema/union.lua

@@ -98,8 +98,10 @@ local function create_union_types(avro_schema, opts)
         if type == 'null' then
             is_nullable = true
         else
-            local variant_type = convert(type, {context = context})
             local box_field_name = type.name or avro_helpers.avro_type(type)
+            table.insert(context.path, box_field_name)
+            local variant_type = convert(type, {context = context})
+            table.remove(context.path, #context.path)
             union_types[#union_types + 1] = box_type(variant_type,
                 box_field_name, {
                     gen_argument = gen_argument,

graphql/core/rules.lua

@@ -549,7 +549,9 @@ function rules.variableUsageAllowed(node, context)
             end
 
             if not isTypeSubTypeOf(variableType, argumentType) then
-              error('Variable type mismatch')
+              error(('Variable "%s" type mismatch: expected "%s", got "%s"')
+                :format(variableName, tostring(variableType.name),
+                tostring(argumentType.name)))
             end
           elseif argument.value.kind == 'inputObject' then
             for _, child in ipairs(argument.value.values) do

test/testdata/common_testdata.lua

@@ -1566,9 +1566,11 @@ function common_testdata.run_queries(gql_wrapper)
             }
         }
     ]]
-    local ok, err = pcall(gql_wrapper.compile, gql_wrapper, query_20)
+    local ok, _ = pcall(gql_wrapper.compile, gql_wrapper, query_20)
     test:is(ok, true, 'correct variable usage as InputUnion')
 
+    -- XXX: add offset (non-null argument) case: make proper error is the case
+
     -- }}}
 
     assert(test:check(), 'check plan')

test/testdata/compound_index_testdata.lua

@@ -1318,7 +1318,7 @@ function compound_index_testdata.run_queries(gql_wrapper)
     -- (top-level collection, full primary key)
 
     local query_6 = [[
-        query users($limit: Int, $user_str: String, $user_num: Long) {
+        query users($limit: Int, $user_str: String!, $user_num: Long!) {
             user_collection(limit: $limit, offset: {user_str: $user_str,
                     user_num: $user_num}) {
                 user_str