The Compiler

A short introduction of the Relay Compiler

Relay's compiler is responsible for taking all GraphQL operations defined in your code, analyze their relationships and check their validity. It then compiles them to generated files containing optimized artifacts that Relay uses at runtime to make queries and understand the response. This means that Relay moves work like parsing and understanding how responses to queries are structured to compile time. A good example of how Relay treats performance as a core feature.

In addition to emitting runtime artifacts, the compiler also emits ReScript types through RescriptRelay's language plugin for the compiler, describing your operations and their relationships. RescriptRelay takes these types and uses them to enforce type safety. This means that Relay and RescriptRelay can guarantee type-safety when interacting with all data, and that you'll get a great developer experience through the tooling that types enable.

As said before, you really don't have to think about the generated artifacts as RescriptRelay does the heavy lifting of using them for you, but if you're interested, have a look at the files in your artifactDirectory.

You can read more about the Relay compiler here.

How RescriptRelay uses the Relay compiler

When you run the compiler, you run rescript-relay-compiler and not relay-compiler - why is that? Well, it's because RescriptRelay ships a thin layer on top of relay-compiler, that sets up the configuration the Relay compiler needs to produce ReScript automatically. It also enforces a more strict configuration of Relay that RescriptRelay needs to do its thing.