- document semantic nullability support in resolvers

Reviewed By: captbaritone

Differential Revision: D65289273

fbshipit-source-id: c5ba813b1d80c57a009619a3c9dbf7b5976cf701

website/docs/guides/relay-resolvers/errors.md

@@ -2,7 +2,7 @@
 id: errors
 title: "Error Handling"
 slug: /guides/relay-resolvers/errors/
-description: How Relay handles errors throw by resolvers
+description: How Relay handles errors thrown by resolvers
 ---
 
 Just like GraphQL servers, Relay Resolvers support field-level error handling. If an individual resolver throws an error, when that field is read, Relay will log that error to the environment's user-provided `relayFieldLogger` logger, and the field will become null.
@@ -46,3 +46,19 @@ const environment = new Environment({
 :::note
 [Live Resolvers](./live-fields.md) can potentially throw errors when they are first evaluated or when their `.read()` method is called. Both types of errors will be handled identically by Relay.
 :::
+
+## Support for Semantic Nullability
+
+Relay resolver fields can be specified as [semantically non-null](../../semantic-nullability/) just like server schema fields. Developers can add the directive `@semanticNonNull` in the docblock of a relay resolver in order to indicate that the field is non-nullable in the semantic sense, but that the client should still be prepared to handle errors.
+
+For example:
+```ts
+/**
+ * @RelayResolver RelayExample.semantic_non_null_field: String @semanticNonNull
+ */
+export function semantic_non_null_field(
+  model: RelayExampleModel,
+): string {
+  return model.someField ?? 'field was null, this is the default';
+}
+```

website/docs/guides/relay-resolvers/limitations.md

@@ -11,10 +11,6 @@ Relay Resolvers are do have some limitations. Here we will collect a list of kno
 
 In a full GraphQL implementation, resolvers would have access to an `info` argument. This argument is not available in Relay Resolvers today.
 
-## All fields must be nullable
-
-Today all resolvers must be typed as nullable in order to support coercing errors to null without having to implement null bubbling. In the future we intend Resolvers to support some version of [strict semantic nullability](https://github.com/graphql/graphql-wg/discussions/1410).
-
 ## Not all GraphQL constructs are supported
 
 Today Relay Resolvers only support a subset of GraphQL constructs. For example, it's not currently possible to define input types, enums or interfaces using Relay Resolvers.

website/versioned_docs/version-v18.0.0/guides/relay-resolvers/errors.md

@@ -46,3 +46,19 @@ const environment = new Environment({
 :::note
 [Live Resolvers](./live-fields.md) can potentially throw errors when they are first evaluated or when their `.read()` method is called. Both types of errors will be handled identically by Relay.
 :::
+
+## Support for Semantic Nullability
+
+Relay resolver fields can be specified as [semantically non-null](../../semantic-nullability/) just like server schema fields. Developers can add the directive `@semanticNonNull` in the docblock of a relay resolver in order to indicate that the field is non-nullable in the semantic sense, but that the client should still be prepared to handle errors.
+
+For example:
+```ts
+/**
+ * @RelayResolver RelayExample.semantic_non_null_field: String @semanticNonNull
+ */
+export function semantic_non_null_field(
+  model: RelayExampleModel,
+): string {
+  return model.someField ?? 'field was null, this is the default';
+}
+```

website/versioned_docs/version-v18.0.0/guides/relay-resolvers/limitations.md

@@ -11,10 +11,6 @@ Relay Resolvers are do have some limitations. Here we will collect a list of kno
 
 In a full GraphQL implementation, resolvers would have access to an `info` argument. This argument is not available in Relay Resolvers today.
 
-## All fields must be nullable
-
-Today all resolvers must be typed as nullable in order to support coercing errors to null without having to implement null bubbling. In the future we intend Resolvers to support some version of [strict semantic nullability](https://github.com/graphql/graphql-wg/discussions/1410).
-
 ## Not all GraphQL constructs are supported
 
 Today Relay Resolvers only support a subset of GraphQL constructs. For example, it's not currently possible to define input types, enums or interfaces using Relay Resolvers.