Add allowOperation to batchMiddleware.

Author: richardwu

src/index.d.ts

@@ -148,6 +148,7 @@ export type BatchMiddlewareOpts = {
   maxBatchSize?: number;
   maxRequestsPerBatch?: number;
   allowMutations?: boolean;
+  allowOperation?: (operation: ConcreteBatch) => boolean;
   method?: 'POST' | 'GET';
   headers?: Headers | Promise<Headers> | ((req: RelayRequestBatch) => Headers | Promise<Headers>);
   // Available request modes in fetch options. For details see https://fetch.spec.whatwg.org/#requests

src/middlewares/__tests__/batch-test.js

@@ -438,6 +438,60 @@ describe('middlewares/batch', () => {
     });
   });
 
+  describe('option `allowOperation`', () => {
+    beforeEach(() => {
+      fetchMock.restore();
+    });
+
+    it('should not batch requests that return false', async () => {
+      fetchMock.mock({
+        matcher: '/graphql',
+        response: {
+          status: 200,
+          body: { data: {} },
+        },
+        method: 'POST',
+      });
+      fetchMock.mock({
+        matcher: '/graphql/batch',
+        response: {
+          status: 200,
+          body: [{ data: {} }, { data: {} }],
+        },
+        method: 'POST',
+      });
+
+      const req1 = mockReq(1, {
+        query: 'abc',
+      });
+      const req2 = mockReq(2);
+      const req3 = mockReq(3);
+      const req4 = mockReq(4, {
+        query: 'def',
+      });
+      const req5 = mockReq(4, {
+        query: 'no',
+      });
+
+      const rnl = new RelayNetworkLayer([
+        batchMiddleware({
+          allowOperation: (op) => !['abc', 'def'].includes(op.name),
+        }),
+      ]);
+      await Promise.all([
+        req1.execute(rnl),
+        req2.execute(rnl),
+        req3.execute(rnl),
+        req4.execute(rnl),
+        req5.execute(rnl),
+      ]);
+      const batchReqs = fetchMock.calls('/graphql/batch');
+      const singleReqs = fetchMock.calls('/graphql');
+      expect(batchReqs).toHaveLength(1);
+      expect(singleReqs).toHaveLength(2);
+    });
+  });
+
   it('should pass fetch options', async () => {
     fetchMock.mock({
       matcher: '/graphql/batch',

src/middlewares/batch.js

@@ -59,6 +59,7 @@ export default function batchMiddleware(options?: BatchMiddlewareOpts): Middlewa
   const batchUrl = opts.batchUrl || '/graphql/batch';
   const maxBatchSize = opts.maxBatchSize || DEFAULT_BATCH_SIZE;
   const maxRequestsPerBatch = opts.maxRequestsPerBatch || 0; // 0 is the same as no limit
+  const allowOperation = opts.allowOperation || true;
   const singleton = {};
 
   const fetchOpts = {};
@@ -81,6 +82,10 @@ export default function batchMiddleware(options?: BatchMiddlewareOpts): Middlewa
       );
     }
 
+    if (isFunction(opts.allowOperation) && !opts.allowOperation(req.operation)) {
+      return next(req);
+    }
+
     // req with FormData can not be batched
     if (req.isFormData()) {
       return next(req);
@@ -97,6 +102,7 @@ export default function batchMiddleware(options?: BatchMiddlewareOpts): Middlewa
       singleton,
       maxBatchSize,
       maxRequestsPerBatch,
+      allowOperation,
       fetchOpts,
     });
   };