fix: error thrown for nullable field resolving null

Closes #22
mesosphere · Mar 6, 2019 · af83c91 · af83c91
1 parent d4cca0b
commit af83c91
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Showing 2 changed files with 33 additions and 2 deletions.
diff --git a/src/__tests__/graphqlObservable-test.ts b/src/__tests__/graphqlObservable-test.ts
@@ -99,6 +99,7 @@ const fieldResolverSchema = makeExecutableSchema({
 
     type Item {
       nodeFieldResolver: ObjectValue!
+      nullableNodeFieldResolver: ObjectValue
       giveMeTheParentFieldResolver: ObjectValue!
       giveMeTheArgsFieldResolver(arg: String!): ObjectValue!
       giveMeTheContextFieldResolver: ObjectValue!
@@ -139,6 +140,9 @@ const fieldResolverSchema = makeExecutableSchema({
       nodeFieldResolver() {
         return of({ value: "I am a node field resolver" });
       },
+      nullableNodeFieldResolver() {
+        return null;
+      },
       giveMeTheParentFieldResolver(parent) {
         return of({ value: JSON.stringify(parent) });
       },
@@ -488,6 +492,29 @@ describe("graphqlObservable", function() {
           m.expect(result.pipe(take(1))).toBeObservable(expected);
         });
 
+        itMarbles("if nullable field resolver returns null, it resolves null", function(m) {
+          const query = gql`
+            query {
+              item {
+                nullableNodeFieldResolver {
+                  value
+                }
+              }
+            }
+          `;
+          const expected = m.cold("(a|)", {
+            a: {
+              data: {
+                item: {
+                  nullableNodeFieldResolver: null
+                }
+              }
+            }
+          });
+          const result = graphql(fieldResolverSchema, query, null, {});
+          m.expect(result.pipe(take(1))).toBeObservable(expected);
+        });
+
         itMarbles("the field resolvers 1st argument is parent", function(m) {
           const query = gql`
             query {

diff --git a/src/reactive-graphql.ts b/src/reactive-graphql.ts
@@ -20,7 +20,8 @@ import {
   isScalarType,
   isEnumType,
   isObjectType,
-  parse
+  isNonNullType,
+  parse,
 } from "graphql";
 
 // WARNING: This is NOT a spec complete graphql implementation
@@ -145,7 +146,10 @@ export default function graphql<T = object>(
       return resolvedObservable.pipe(
         concatMap(emitted => {
           if (!emitted) {
-            return throwObservable("resolver emitted empty value");
+            if (isNonNullType(type)) {
+              return throwObservable(`resolver for ${field.name} emitted empty value`);
+            }
+            return of(null);
           }
 
           if (emitted instanceof Array) {