Merge pull request #3193 from smolinari/patch-1

docs(resolvers-map): add notes about missing non-value types for nullable fields and args

Author: kamilmysliwiec

content/graphql/resolvers-map.md

@@ -269,6 +269,8 @@ getAuthor(
 ) {}
 ```
 
+> info **Hint** In the case of `firstName`, which is a GraphQL nullable field, it isn't necessary to add the non-value types of `null` or `undefined` to the type of this field. Just be aware, you'll need to type guard for these possible non-value types in your resolvers, because a GraphQL nullable field will allow those types to pass through to your resolver.
+
 #### Dedicated arguments class
 
 With inline `@Args()` calls, code like the example above becomes bloated. Instead, you can create a dedicated `GetAuthorArgs` arguments class and access it in the handler method as follows:
@@ -295,7 +297,7 @@ class GetAuthorArgs {
 }
 ```
 
-> info **Hint** Again, due to TypeScript's metadata reflection system limitations, it's required to either use the `@Field` decorator to manually indicate type and optionality, or use a [CLI plugin](/graphql/cli-plugin).
+> info **Hint** Again, due to TypeScript's metadata reflection system limitations, it's required to either use the `@Field` decorator to manually indicate type and optionality, or use a [CLI plugin](/graphql/cli-plugin). Also, in the case of `firstName`, which is a GraphQL nullable field, it isn't necessary to add the non-value types of `null` or `undefined` to the type of this field. Just be aware, you'll need to type guard for these possible non-value types in your resolvers, because a GraphQL nullable field will allow those types to pass through to your resolver. 
 
 This will result in generating the following part of the GraphQL schema in SDL: