fix: preserve component props when className.target is false (#226)

* test: add breaking test

* fix: preserve left/right props on deepMergeConfig

Author: jamsch

src/__tests__/native/components.test.tsx

@@ -0,0 +1,56 @@
+import { Button as RNButton, type ButtonProps } from "react-native";
+
+import { render } from "@testing-library/react-native";
+import { copyComponentProperties } from "react-native-css/components/copyComponentProperties";
+import { registerCSS, testID } from "react-native-css/jest";
+import { useCssElement } from "react-native-css/native";
+import type {
+  StyledConfiguration,
+  StyledProps,
+} from "react-native-css/runtime.types";
+
+test("Component preserves props when mapping specifies 'target: false'", () => {
+  registerCSS(`.sign-in { color: orange; }`);
+
+  const mapping: StyledConfiguration<typeof RNButton> = {
+    className: {
+      target: false,
+      nativeStyleMapping: {
+        color: "color",
+      },
+    },
+  };
+
+  const Button = copyComponentProperties(
+    RNButton,
+    (props: StyledProps<ButtonProps, typeof mapping>) => {
+      return useCssElement(RNButton, props, mapping);
+    },
+  );
+
+  const onPress = jest.fn();
+
+  const result = render(
+    <Button
+      testID={testID}
+      className="sign-in"
+      title="Sign In"
+      onPress={onPress}
+    />,
+  );
+
+  expect(result.getByText("Sign In")).toBeTruthy();
+
+  const renderedElement = result.getByTestId(testID);
+  const renderedProps = renderedElement.props;
+
+  expect(renderedProps.testID).toBe(testID);
+  expect(renderedProps).not.toHaveProperty("className");
+
+  // the <Text> element in the RN button
+  // should apply an orange color to the element (because of the "sign-in" className)
+  const titleElement = result.getByText("Sign In");
+  expect(titleElement.props.style).toBeInstanceOf(Array);
+  expect(titleElement.props.style).toHaveLength(2);
+  expect(titleElement.props.style[1]).toEqual({ color: "#ffa500" });
+});

src/native/styles/index.ts

@@ -362,7 +362,7 @@ function deepMergeConfig(
       result = Object.assign({}, left, right);
     }
   } else {
-    result = { ...left };
+    result = Object.assign({}, left, right);
   }
 
   if (