feat: Removes peer dependency on react-test-renderer. (#26)

Author: kpsroka

__tests__/__snapshots__/snapshotDiff.test.js.snap

@@ -129,3 +129,8 @@ exports[`diffs short strings 1`] = `
 +   abcy
     "
 `;
+
+exports[`failed optional deps throws with sensible message on missing react-test-renderer 1`] = `
+"Failed to load optional module \\"react-test-renderer\\". If you need to compare React elements, please add \\"react-test-renderer\\" to your project's dependencies.
+Cannot find module 'non-existent-module-for-testing' from 'snapshotDiff.test.js'"
+`;

__tests__/snapshotDiff.test.js

@@ -153,3 +153,24 @@ test('can use contextLines with React components', () => {
     })
   ).toMatchSnapshot();
 });
+
+describe('failed optional deps', () => {
+  beforeEach(() => {
+    jest.mock('react-test-renderer', () => {
+      // $FlowFixMe -- this is intended.
+      require('non-existent-module-for-testing'); // eslint-disable-line
+    });
+  });
+
+  afterEach(() => {
+    jest.resetModules();
+  });
+
+  test('throws with sensible message on missing react-test-renderer', () => {
+    const testComponentA = <Component test="a" />;
+    const testComponentB = <Component test="b" />;
+    expect(() =>
+      snapshotDiff(testComponentA, testComponentB)
+    ).toThrowErrorMatchingSnapshot();
+  });
+});

package.json

@@ -16,8 +16,7 @@
   },
   "repository": "https://github.com/thymikee/snapshot-diff",
   "peerDependencies": {
-    "jest": ">=16",
-    "react-test-renderer": ">=15"
+    "jest": ">=16"
   },
   "dependencies": {
     "jest-diff": "^22.0.6",

src/index.js

@@ -58,8 +58,24 @@ function diffStrings(valueA: any, valueB: any, options: Options) {
   });
 }
 
+function requireReactTestRenderer() {
+  try {
+    return require('react-test-renderer'); // eslint-disable-line import/no-extraneous-dependencies
+  } catch (error) {
+    if (error.code === 'MODULE_NOT_FOUND') {
+      throw new Error(
+        `Failed to load optional module "react-test-renderer". ` +
+          `If you need to compare React elements, please add "react-test-renderer" to your ` +
+          `project's dependencies.\n` +
+          `${error.message}`
+      );
+    }
+    throw error;
+  }
+}
+
 function diffReactComponents(valueA: any, valueB: any, options: Options) {
-  const renderer = require('react-test-renderer');
+  const renderer = requireReactTestRenderer();
   const reactValueA = renderer.create(valueA).toJSON();
   const reactValueB = renderer.create(valueB).toJSON();
   const prettyFormatOptions = { plugins: [ReactElement], min: true };