Merge pull request #417 from dfuse-io/fix/subscription-panic-in-resolver

Fixed `reflect.Value.Type on zero Value` panic when subscription resolver itself panics

Author: pavelnikolov

internal/exec/exec.go

@@ -39,7 +39,7 @@ type extensionser interface {
 }
 
 func makePanicError(value interface{}) *errors.QueryError {
-	return errors.Errorf("graphql: panic occurred: %v", value)
+	return errors.Errorf("panic occurred: %v", value)
 }
 
 func (r *Request) Execute(ctx context.Context, s *resolvable.Schema, op *query.Operation) ([]byte, []*errors.QueryError) {
@@ -326,7 +326,7 @@ func (r *Request) execList(ctx context.Context, sels []selected.Selection, typ *
 				r.execSelectionSet(ctx, sels, typ.OfType, &pathSegment{path, i}, s, resolver.Index(i), &entryouts[i])
 			}(i)
 		}
-		for i := 0; i < concurrency;i++ {
+		for i := 0; i < concurrency; i++ {
 			sem <- struct{}{}
 		}
 	} else {

internal/exec/subscribe.go

@@ -61,6 +61,11 @@ func (r *Request) Subscribe(ctx context.Context, s *resolvable.Schema, op *query
 		}
 	}()
 
+	// Handles the case where the locally executed func above panicked
+	if len(r.Request.Errs) > 0 {
+		return sendAndReturnClosed(&Response{Errors: r.Request.Errs})
+	}
+
 	if f == nil {
 		return sendAndReturnClosed(&Response{Errors: []*errors.QueryError{err}})
 	}

subscription_test.go

@@ -543,3 +543,33 @@ func TestSchemaSubscribe_CustomResolverTimeout(t *testing.T) {
 		},
 	})
 }
+
+type subscriptionsPanicInResolver struct{}
+
+func (r *subscriptionsPanicInResolver) OnPanic() <-chan string {
+	panic("subscriptionsPanicInResolver")
+}
+
+func TestSchemaSubscribe_PanicInResolver(t *testing.T) {
+	r := &struct {
+		*subscriptionsPanicInResolver
+	}{
+		subscriptionsPanicInResolver: &subscriptionsPanicInResolver{},
+	}
+	gqltesting.RunSubscribe(t, &gqltesting.TestSubscription{
+		Schema: graphql.MustParseSchema(`
+			type Query {}
+			type Subscription {
+				onPanic : String!
+			}
+		`, r),
+		Query: `
+			subscription {
+				onPanic
+			}
+		`,
+		ExpectedResults: []gqltesting.TestResponse{
+			{Errors: []*qerrors.QueryError{{Message: "panic occurred: subscriptionsPanicInResolver"}}},
+		},
+	})
+}