It appears that you're encountering an issue while attempting to create a Sitecore JSS app using the nextjs template for Sitecore 10.3. The error message you provided indicates a problem related to GraphQL and the usage of the "App" GraphQLObjectType.
The specific error message, "Cannot use GraphQLObjectType 'App' from another module or realm," suggests that there might be a conflict in the dependencies of GraphQL within your project.
Here's how you could approach resolving this issue:
Check Dependencies: Make sure you're not using conflicting or multiple versions of the
graphql package in your project. Inconsistent versions of GraphQL can lead to unexpected issues. You can inspect your project's
package-lock.json files to identify potential conflicting dependencies.
Resolutions: Consider using Yarn's selective version resolutions to ensure that only one version of the
graphql package is used throughout your project. This can help mitigate conflicts arising from multiple versions of the same package. The error message you received provides a link to the Yarn documentation on how to set up resolutions.
Dependency Tree: Examine your project's dependency tree to see if any other packages are indirectly bringing in different versions of GraphQL. You can use tools like
yarn why graphql or
npm ls graphql to identify which packages are depending on GraphQL and causing potential conflicts.
Clean Cache: Sometimes, issues can be resolved by clearing the package manager's cache and reinstalling dependencies. You can do this by running
yarn cache clean or
npm cache clean followed by
yarn install or
Update Packages: Ensure that all the packages and dependencies in your project are up to date. Outdated packages could potentially introduce compatibility issues.
Community Forums: If the issue persists, it might be helpful to consult the Sitecore community forums or any official documentation related to Sitecore JSS and Next.js integration. Others who have encountered a similar issue might have shared their solutions.
Remember to back up your project or create a snapshot before making significant changes to your dependencies, as modifying dependencies can sometimes lead to other unforeseen issues. If the problem persists, reaching out to Sitecore support or their community forums could provide you with more tailored assistance.
Hope this might help you, please let me know if you still have issues.