[Feature] clone jest-next-dynamic (#2)

.babelrc.js

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+module.exports = {
+  presets: ["next/babel"],
+  plugins: ["babel-plugin-dynamic-import-node"]
+};

.gitignore

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+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Runtime data
+pids
+*.pid
+*.seed
+*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+lib-cov
+
+# Coverage directory used by tools like istanbul
+coverage
+
+# nyc test coverage
+.nyc_output
+
+# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+bower_components
+
+# node-waf configuration
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+build/Release
+
+# Dependency directories
+node_modules/
+jspm_packages/
+
+# TypeScript v1 declaration files
+typings/
+
+# Optional npm cache directory
+.npm
+
+# Optional eslint cache
+.eslintcache
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
+*.tgz
+
+# Yarn Integrity file
+.yarn-integrity
+
+# dotenv environment variables file
+.env
+
+# Build cache
+.cache
+
+# next.js build output
+.next
+
+## Test result
+__snapshots__

index.js

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+const mockInitializers = [];
+
+module.exports = function preloadAll() {
+  if (mockInitializers.length) {
+    // Copy and empty out `mockInitializers` right away so that any newly
+    // enqueued components are found in the next pass.
+    const initializers = mockInitializers.slice();
+    mockInitializers.length = 0;
+    // While loading the components in this round of initializers, more
+    // components may have been dynamically imported, adding more initializers
+    // we should run and await.
+    return Promise.all(initializers.map(preload => preload())).then(preloadAll);
+  } else {
+    return Promise.resolve();
+  }
+};
+
+function createFactory(moduleName) {
+  return () => {
+    const dynamicModule = jest.requireActual(moduleName);
+    const dynamic = dynamicModule.default;
+
+    const mockDynamic = (loader, options) => {
+      // Remove webpack-specific functionality added by the next/babel preset.
+      if (loader && typeof loader === "object" && loader.loadableGenerated) {
+        const { loadableGenerated, ...mockLoader } = loader;
+        loader = mockLoader;
+      }
+      if (options && typeof options === "object" && options.loadableGenerated) {
+        const { loadableGenerated, ...mockOptions } = options;
+        options = mockOptions;
+      }
+      const LoadableComponent = dynamic(loader, options);
+      mockInitializers.push(() =>
+        LoadableComponent.preload
+          ? LoadableComponent.preload()
+          : LoadableComponent.render.preload());
+      return LoadableComponent;
+    };
+
+    // Replace the `default` export on the existing module so that other exports
+    // and non-enumerable properties remain.
+    dynamicModule.default = mockDynamic;
+    return dynamicModule;
+  };
+}
+
+// In order to more easily include this feature in shared Jest setups (like
+// presets), use `virtual: true` to avoid throwing an error when `next` isn't
+// actually installed or it's a version without `next-server` (introduced in
+// Next.js 8).
+for (const moduleName of ["next/dynamic", "next-server/dynamic"]) {
+  jest.doMock(moduleName, createFactory(moduleName), { virtual: true });
+}

index.test.js

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+import React from "react";
+import TestRenderer from "react-test-renderer";
+import preloadAll from "./index";
+import NextDynamicNested from "./test/NextDynamicNested";
+
+beforeAll(async () => {
+  await preloadAll();
+});
+
+it("renders nested next/dynamic components", () => {
+  expect(TestRenderer.create(<NextDynamicNested />).toJSON()).toMatchSnapshot();
+});