`_interopRequireDefault Is Not A Function` When Loading Local File

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Introduction

When upgrading to React Native 0.79.1 and Metro 0.82.1, developers may encounter a peculiar issue where importing local files using the index.ts file as an entry point results in a _interopRequireDefault is not a function error. This issue arises due to the introduction of package export support in Metro 0.82.1, which is enabled by default. In this article, we will delve into the root cause of this problem and explore possible solutions to resolve it.

Understanding the Issue

The error _interopRequireDefault is not a function occurs when the Metro bundler attempts to resolve the import statement using the index.ts file as an entry point. This file is responsible for exporting the default component, which is then imported by the screen. However, with the introduction of package export support in Metro 0.82.1, the bundler starts to treat the index.ts file as a package, leading to the error.

Reproducing the Issue

To reproduce the issue, follow these steps:

  1. Create a React Native project using the latest version of React Native (0.79.1) and Metro (0.82.1).
  2. Create a subfolder within the project directory, e.g., components.
  3. Inside the components folder, create an index.ts file that exports the default component, e.g., WarningModal.
  4. In the screen, import the WarningModal component using the index.ts file as an entry point, e.g., import { WarningModal } from './components';.
  5. Run the app and observe the _interopRequireDefault is not a function error.

Possible Solutions

To resolve the issue, try the following solutions:

1. Disable Package Export Support

As mentioned earlier, package export support is enabled by default in Metro 0.82.1. To disable it, add the following configuration to your metro.config.js file:

module.exports = {
  // ...
  resolver: {
    unstable_enablePackageExports: false,
  },
};

This will disable package export support, and the import statement should work as expected.

2. Use a Different Import Statement

Instead of using the index.ts file as an entry point, try importing the component directly from the file, e.g., import WarningModal from './components/warning_modal';. This should bypass the package export support and resolve the issue.

3. Update the index.ts File

If you're using a recent version of TypeScript, you may need to update the index.ts file to use the export * from syntax instead of the export { default as WarningModal } from syntax. This will ensure that the component is exported correctly and can be imported using the index.ts file as an entry point.

Conclusion

The _interopRequireDefault is not a function error when loading local files using the index.ts file as an entry point is a known issue in React Native 0.79.1 and Metro 0.82.1. To resolve this issue, try disabling package export support, using a different import statement, or updating the index.ts file to use the export * from syntax. By following these solutions, you should be able to resolve the issue and continue developing your React Native app.

Additional Resources

Troubleshooting Tips

  • Make sure you're using the latest version of React Native and Metro.
  • Verify that the index.ts file is correctly exporting the default component.
  • Check the import statement to ensure it's using the correct file path and syntax.
  • If you're still experiencing issues, try disabling package export support or using a different import statement.
    _interopRequireDefault is not a function when loading local file: Q&A =====================================================

Introduction

In our previous article, we explored the issue of _interopRequireDefault is not a function when loading local files using the index.ts file as an entry point in React Native 0.79.1 and Metro 0.82.1. In this article, we will provide a Q&A section to help you better understand the issue and its solutions.

Q: What is the root cause of the _interopRequireDefault is not a function error?

A: The root cause of the error is the introduction of package export support in Metro 0.82.1, which is enabled by default. This feature treats the index.ts file as a package, leading to the error.

Q: How can I reproduce the issue?

A: To reproduce the issue, follow these steps:

  1. Create a React Native project using the latest version of React Native (0.79.1) and Metro (0.82.1).
  2. Create a subfolder within the project directory, e.g., components.
  3. Inside the components folder, create an index.ts file that exports the default component, e.g., WarningModal.
  4. In the screen, import the WarningModal component using the index.ts file as an entry point, e.g., import { WarningModal } from './components';.
  5. Run the app and observe the _interopRequireDefault is not a function error.

Q: What are the possible solutions to resolve the issue?

A: There are three possible solutions to resolve the issue:

  1. Disable Package Export Support: Add the following configuration to your metro.config.js file:
module.exports = {
  // ...
  resolver: {
    unstable_enablePackageExports: false,
  },
};

This will disable package export support, and the import statement should work as expected.

  1. Use a Different Import Statement: Instead of using the index.ts file as an entry point, try importing the component directly from the file, e.g., import WarningModal from './components/warning_modal';. This should bypass the package export support and resolve the issue.

  2. Update the index.ts File: If you're using a recent version of TypeScript, you may need to update the index.ts file to use the export * from syntax instead of the export { default as WarningModal } from syntax. This will ensure that the component is exported correctly and can be imported using the index.ts file as an entry point.

Q: Why is this issue specific to React Native 0.79.1 and Metro 0.82.1?

A: This issue is specific to React Native 0.79.1 and Metro 0.82.1 because of the introduction of package export support in Metro 0.82.1. This feature is not available in earlier versions of Metro, and therefore, the issue does not occur in those versions.

Q: Can I use a workaround to resolve the issue?

A: Yes, you can use a workaround to resolve the issue. One possible workaround is to use a different import statement, such as import WarningModal from './components/warning_modal';. This should bypass the package export support and resolve the issue.

Q How can I prevent this issue from occurring in the future?

A: To prevent this issue from occurring in the future, you can disable package export support by adding the following configuration to your metro.config.js file:

module.exports = {
  // ...
  resolver: {
    unstable_enablePackageExports: false,
  },
};

This will ensure that the index.ts file is not treated as a package, and the import statement should work as expected.

Conclusion

The _interopRequireDefault is not a function error when loading local files using the index.ts file as an entry point is a known issue in React Native 0.79.1 and Metro 0.82.1. By understanding the root cause of the issue and using the possible solutions, you can resolve the issue and continue developing your React Native app.