Using GraphQL Codegen Typed Document Node Fragment to Create a Query

Learn how to effectively use `GraphQL Code Generator` to create queries with typed DocumentNode fragments, and explore common errors and solutions.
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Solving the Problem of Creating Queries with GraphQL Codegen Typed Document Nodes

When working with GraphQL, developers often utilize fragments to modularize their queries and share reusable pieces of code. However, there can be some hurdles when using GraphQL Code Generator alongside Typed Document Node Fragments. If you've encountered an error while trying to integrate a fragment into a query, you are not alone. In this post, we'll walk through the situation step by step, exploring both the problem and the effective solution.

The Challenge: Generating Queries with Fragments

Typically, you might have defined a fragment with the GraphQL Code Generator, resulting in an object like this:

[[See Video to Reveal this Text or Code Snippet]]

This fragment object should theoretically allow you to create a GraphQL query as shown below:

[[See Video to Reveal this Text or Code Snippet]]

However, you might encounter a frustrating error that states:

"Cannot read properties of undefined (reading 'source')"

After some investigation, it becomes clear that the issue arises from the fragment object missing certain properties that the gql template literal expects.

Understanding the Issue

The discrepancy lies in the loc and source properties. A standard fragment created using the gql template literal includes these properties, enabling proper recognition by the GraphQL client. For example, a standard fragment looks like this:

[[See Video to Reveal this Text or Code Snippet]]

This structure includes a loc property that contains metadata, crucial for the execution of queries. Your generated MMovieConnectionFragmentDoc lacks this structure, leading to the error when you try to use it in the query.

The Solution: Wrapping the Fragment for Successful Query Creation

Despite this challenge, there is a straightforward way to utilize the generated fragment in your queries successfully. The trick is to convert the fragment back to a string and wrap it in gql to add those necessary properties. Here’s how you can do it:

Step-by-Step Guide

Import the required libraries:
If you’re using graphql, make sure to include it in your imports.

[[See Video to Reveal this Text or Code Snippet]]

Convert the Document Node:

[[See Video to Reveal this Text or Code Snippet]]

Create the Query with the Fragment:
Integrate your fragment into the query seamlessly:

[[See Video to Reveal this Text or Code Snippet]]

By following these steps, you can circumvent the limitations imposed by the missing properties in the generated DocumentNode and successfully create a query using your typed fragment.

Conclusion

In conclusion, while working with GraphQL Code Generator and typed fragments, you may run into certain challenges due to missing properties like loc and source. By wrapping your DocumentNode fragments in gql after converting them back to a string, you can create robust and reusable GraphQL queries without encountering the usual pitfalls.

Feel free to share your experiences with GraphQL and the GraphQL Code Generator in the comments below, and let’s help each other navigate this powerful technology!