feat(UserInputError): handle unhandled errors. (#5508)

Co-authored-by: David Glasser <glasser@davidglasser.net>

CHANGELOG.md

@@ -9,6 +9,9 @@ The version headers in this history reflect the versions of Apollo Server itself
 
 ## vNEXT
 
+- `apollo-server-core`: If a client does not provide a value or provides null for a variable declared to be non-null, this is now reported as an error with an `extensions.code` of `BAD_USER_INPUT` rather than `INTERNAL_SERVER_ERROR`. (This is similar to a change we made in v2.23.0 for variables that are sent as the wrong type.) [PR #5508](https://github.com/apollographql/apollo-server/pull/5508) [Issue #5353](https://github.com/apollographql/apollo-server/issues/5353)
+
+
 ## v3.0.2
 
 - `apollo-server-types`: TypeScript typings for `info.cacheControl` are now added to `GraphQLResolveInfo` as part of `apollo-server-types` rather than a nested file in `apollo-server-core`, and the field now has a named type, `ResolveInfoCacheControl`. [PR #5512](https://github.com/apollographql/apollo-server/pull/5512)

packages/apollo-server-core/src/requestPipeline.ts

@@ -378,16 +378,32 @@ export async function processGraphQLRequest<TContext>(
 
       // The first thing that execution does is coerce the request's variables
       // to the types declared in the operation, which can lead to errors if
-      // they are of the wrong type. We change any such errors into
-      // UserInputError so that their code doesn't end up being
-      // INTERNAL_SERVER_ERROR, since these are client errors.
+      // they are of the wrong type. It also makes sure that all non-null
+      // variables are required and get non-null values. If any of these thingss
+      // lead to errors, we change them into UserInputError so that their code
+      // doesn't end up being INTERNAL_SERVER_ERROR, since these are client
+      // errors.
+      //
+      // This is hacky! Hopefully graphql-js will give us a way to separate
+      // variable resolution from execution later; see
+      // https://github.com/graphql/graphql-js/issues/3169
       const resultErrors = result.errors?.map((e) => {
         if (
           e.nodes?.length === 1 &&
           e.nodes[0].kind === Kind.VARIABLE_DEFINITION &&
-          e.message.startsWith(
+          (e.message.startsWith(
             `Variable "$${e.nodes[0].variable.name.value}" got invalid value `,
-          )
+          ) ||
+            (e.nodes[0].type.kind === Kind.NON_NULL_TYPE &&
+              e.nodes[0].type.type.kind === Kind.NAMED_TYPE &&
+              (e.message.startsWith(
+                `Variable "$${e.nodes[0].variable.name.value}" of required ` +
+                  `type "${e.nodes[0].type.type.name.value}!" was not provided.`,
+              ) ||
+                e.message.startsWith(
+                  `Variable "$${e.nodes[0].variable.name.value}" of non-null ` +
+                    `type "${e.nodes[0].type.type.name.value}!" must not be null.`,
+                ))))
         ) {
           return fromGraphQLError(e, {
             errorClass: UserInputError,

packages/apollo-server-integration-testsuite/src/ApolloServer.ts

@@ -343,6 +343,51 @@ export function testApolloServer<AS extends ApolloServerBase>(
         expect(result.errors[0].extensions.code).toBe('BAD_USER_INPUT');
       });
 
+      it('catches required type variable error and returns UserInputError', async () => {
+        const { url: uri } = await createApolloServer({
+          typeDefs: gql`
+            type Query {
+              hello(x: String!): String
+            }
+          `,
+        });
+
+        const apolloFetch = createApolloFetch({ uri });
+
+        const result = await apolloFetch({
+          query: `query ($x:String!) {hello(x:$x)}`,
+        });
+        expect(result.data).toBeUndefined();
+        expect(result.errors).toBeDefined();
+        expect(result.errors[0].message).toMatch(
+          `Variable "$x" of required type "String!" was not provided.`,
+        );
+        expect(result.errors[0].extensions.code).toBe('BAD_USER_INPUT');
+      });
+
+      it('catches non-null type variable error and returns UserInputError', async () => {
+        const { url: uri } = await createApolloServer({
+          typeDefs: gql`
+            type Query {
+              hello(x: String!): String
+            }
+          `,
+        });
+
+        const apolloFetch = createApolloFetch({ uri });
+
+        const result = await apolloFetch({
+          query: `query ($x:String!) {hello(x:$x)}`,
+          variables: { x: null },
+        });
+        expect(result.data).toBeUndefined();
+        expect(result.errors).toBeDefined();
+        expect(result.errors[0].message).toMatch(
+          `Variable "$x" of non-null type "String!" must not be null.`,
+        );
+        expect(result.errors[0].extensions.code).toBe('BAD_USER_INPUT');
+      });
+
       describe('schema creation', () => {
         it('accepts typeDefs and resolvers', async () => {
           const typeDefs = gql`