fixes variable default to null, where it should be undefiend

Changelog.md

@@ -6,6 +6,9 @@
 
 - Removed leftover `apollo-client@beta` peer dep.  <br/>
   [@brentertz](https://github.com/brentertz) in [#3064](https://github.com/apollographql/react-apollo/pull/3064)
+- Stop setting optional input to `null`, when using the `graphql` HOC.  <br/>
+  [@ZhengYuTay](https://github.com/ZhengYuTay) in [#3056](https://github.com/apollographql/react-apollo/pull/3056)
+
 
 ## 2.5.6 (2019-05-22)
 

src/hoc-utils.tsx

@@ -12,10 +12,7 @@ export function getDisplayName<P>(WrappedComponent: React.ComponentType<P>) {
   return WrappedComponent.displayName || WrappedComponent.name || 'Component';
 }
 
-export function calculateVariablesFromProps<TProps>(
-  operation: IDocumentDefinition,
-  props: TProps,
-) {
+export function calculateVariablesFromProps<TProps>(operation: IDocumentDefinition, props: TProps) {
   let variables: OperationVariables = {};
   for (let { variable, type } of operation.variables) {
     if (!variable.name || !variable.name.value) continue;
@@ -30,7 +27,7 @@ export function calculateVariablesFromProps<TProps>(
 
     // Allow optional props
     if (type.kind !== 'NonNullType') {
-      variables[variableName] = null;
+      variables[variableName] = undefined;
     }
   }
   return variables;

test/client/graphql/queries/api.test.tsx

@@ -228,7 +228,7 @@ describe('[queries] api', () => {
         }
       }
     `;
-    const vars1 = { cursor: null };
+    const vars1 = { cursor: undefined };
     const data1 = {
       allPeople: { cursor: 1, people: [{ name: 'Luke Skywalker' }] },
     };