Fix Shopify app Cannot read properties of null error

Are you a Shopify app developer encountering the frustrating “Cannot read properties of null (reading ‘useContext’)” error? You’re not alone. This error can be a roadblock for many developers, especially those new to using the Command Line Interface (CLI) for Shopify app development. In this comprehensive guide, we’ll explore the causes of this error and provide you with practical solutions to get your app development back on track.

Understanding the Error

What Does the Error Mean?

The “Cannot read properties of null (reading ‘useContext’)” error typically occurs when there’s an issue with the React context in your Shopify app. This error suggests that the context you’re trying to access is null, which can happen for various reasons.

Common Scenarios

Incorrect Hook Usage

One of the most common causes of this error is attempting to use the useContext hook outside of a functional component. Remember, React hooks can only be used within the body of a function component.

Context Definition Issues

Another frequent culprit is an improperly defined or incorrectly imported context. Ensure that your context is correctly set up and imported into the component where you’re trying to use it.

Package Compatibility

Sometimes, the error can stem from incompatible versions of React and related packages. It’s crucial to maintain version compatibility across your project dependencies.

Troubleshooting Steps

Verify Your Code Structure

First, double-check your component structure. Make sure you’re using the useContext hook within a functional component. Here’s a quick example of correct usage:

import React, { useContext } from 'react';
import MyContext from './MyContext';

function MyComponent() {
  const contextValue = useContext(MyContext);
  // Rest of your component code
}

Check Context Implementation

Ensure that your context is properly created and provided. Here’s a basic example:

import React, { createContext } from 'react';

const MyContext = createContext(null);

function MyProvider({ children }) {
  // Provide a value to the context
  return <MyContext.Provider value={/* your value here */}>{children}</MyContext.Provider>;
}

export { MyContext, MyProvider };

Update Dependencies

If you suspect package incompatibility, try updating your dependencies. Run the following command in your project directory:

npm update

This will update all packages to their latest compatible versions.

The Most Likely Solution

After investigating various potential causes, the most effective solution to this error appears to be related to a package issue. The accepted solution involves following the steps outlined in a GitHub issue comment:

1. Navigate to your project directory.
2. Run the following command:

npm i @shopify/cli-kit@3.48.0 @shopify/cli@3.48.0 @shopify/app@3.48.0

This command installs specific versions of Shopify CLI packages that are known to resolve the “Cannot read properties of null (reading ‘useContext’)” error.

Additional Considerations

Checking Tutorial Steps

If you’re following a tutorial, such as the one from Gadget.dev for creating a pre-purchase checkout UI extension, it’s worth revisiting the steps to ensure you haven’t missed any crucial details. Small oversights can sometimes lead to unexpected errors.

Exploring Alternative IDEs

While Visual Studio Code (VS Code) is a popular choice for Shopify app development, you might want to try using a different Integrated Development Environment (IDE) if the error persists. Sometimes, IDE-specific settings or extensions can interfere with app functionality.

Leveraging Community Resources

Don’t hesitate to reach out to the Shopify developer community for support. The Shopify Discord community forum can be an invaluable resource for troubleshooting specific issues and getting advice from experienced developers.

Best Practices for Error Prevention

Regular Dependency Audits

Regularly audit and update your project dependencies to ensure you’re using the most stable and compatible versions. You can use the following command to check for outdated packages:

npm outdated

Thorough Testing

Implement comprehensive testing practices in your development workflow. This includes unit tests for individual components and integration tests to catch context-related issues early in the development process.

Staying Informed

Keep up-to-date with the latest Shopify app development best practices and changes to the Shopify CLI. Regularly check the official Shopify developer documentation at https://shopify.dev for updates and new features.

By following these guidelines and implementing the suggested solutions, you should be able to resolve the “Cannot read properties of null (reading ‘useContext’)” error and continue developing your Shopify app with confidence. Remember, persistence and careful debugging are key to overcoming development challenges. Happy coding!