Fixing null pointer exception on DAO update when config is missing

kong/dao/schemas_validation.lua

@@ -75,7 +75,7 @@ function _M.validate_entity(tbl, schema, options)
             if type(v.default) == "function" then
               t[column] = v.default(t)
             else
-              t[column] = v.default
+              t[column] = utils.deep_copy(v.default)
             end
           end
           -- [INSERT_VALUE]

spec/integration/dao/cassandra/base_dao_spec.lua

@@ -594,6 +594,24 @@ describe("Cassandra", function()
           inserted_plugin.consumer_id = nil
         end)
 
+        it("should insert a plugin with an empty config if none is specified", function()
+          local api_t = faker:fake_entity("api")
+          local api, err = dao_factory.apis:insert(api_t)
+          assert.falsy(err)
+          assert.truthy(api)
+
+          local plugin, err = dao_factory.plugins:insert({
+            name = "request-transformer",
+            api_id = api.id
+          })
+
+          assert.falsy(err)
+          assert.truthy(plugin)
+          assert.falsy(plugin.consumer_id)
+          assert.same("request-transformer", plugin.name)
+          assert.same({}, plugin.config)
+        end)
+
         it("should select a plugin configuration by 'null' uuid consumer_id and remove the column", function()
           -- Now we should be able to select this plugin
           local rows, err = dao_factory.plugins:find_by_keys {
@@ -602,7 +620,7 @@ describe("Cassandra", function()
           }
           assert.falsy(err)
           assert.truthy(rows[1])
-          assert.are.same(inserted_plugin, rows[1])
+          assert.same(inserted_plugin, rows[1])
           assert.falsy(rows[1].consumer_id)
         end)
       end)

spec/unit/dao/entities_schemas_spec.lua

@@ -287,6 +287,20 @@ describe("Entities Schemas", function()
       assert.equal("second is not a number", errors["config.second"])
     end)
 
+    it("should have an empty config if none is specified and if the config schema does not have default", function()
+      -- Insert key-auth, whose config has some default values that should be set
+      local plugin = {name = "key-auth", api_id = "stub"}
+      local valid = validate_entity(plugin, plugins_schema, {dao = dao_stub})
+      assert.same({key_names = {"apikey"}, hide_credentials = false}, plugin.config)
+      assert.True(valid)
+
+      -- Insert reauest-transformer, whose default config has no default values, and should be empty
+      local plugin2 = {name = "response-transformer", api_id = "stub"}
+      valid = validate_entity(plugin2, plugins_schema, {dao = dao_stub})
+      assert.same({}, plugin2.config)
+      assert.True(valid)
+    end)
+
     describe("self_check", function()
       it("should refuse `consumer_id` if specified in the config schema", function()
         local stub_config_schema = {