This RFC is an attempt to identify and standardize error codes for GraphQL errors. This has bee previously discussed, and some great work and ideas came out of it. Follow the previous discussion here - #698

Errors ( error codes ) are the silent guardians in the programming world. Though no one wants them in their code, they actually teach us a lot and mold our thinking process. This is especially true for statically typed compiled languages like c, rust etc, where the compiler scolds and guides the programmer to fix the program's syntax. A few strong argument for having a standard set of error codes for GraphQL can be -

1. A well documented set of errors would help developers get a better understanding of the underlying spec. Potential suggestions to fix these errors would help developer productivity.
2. As the spec matures, this would force holistic system thinking and help catch outliers and potential issues. A good amount of effort is being put into creating comparability test suite for the GraphQL spec.

This proposal puts forward the intent to add code key to the standard errors spec in GraphQL. A sample implementation for the same is attached along with a sample output -

"errors": [ { "message": "Query root type must be provided.", "code": "GQ0001" } ]

Sample code to achieve this - https://github.com/shobhitchittora/graphql-js/commit/4fdfa74cbfbbcc01c2316a49ec1b6f1c94987e7c

The idea here is to have a listing of error messages and codes for the below phases of the runtime - Parse, Validate and Execute.

A mapping of all the identified and important errors codes would be kept in a config ( possibly a js module of json file ) like -

const MESSAGE_DETAILS = {
  'Query root type must be provided.': {
    code: 'GQ0001'
  }, 
  ...
}

Some reference in the open where errors have status codes associated for better understanding and traceability.

• React error codes -> https://github.com/facebook/react/blob/master/scripts/error-codes/codes.json
• Rust lang -> https://doc.rust-lang.org/error-index.html
• TypeScript -> https://github.com/microsoft/TypeScript/blob/master/src/compiler/diagnosticMessages.json