allow to provide underlying storage for ssr exchange

.changeset/fluffy-mirrors-pretend.md

@@ -0,0 +1,5 @@
+---
+'@urql/core': minor
+---
+
+allow to provide underlying storage for ssr exchange

packages/core/src/exchanges/ssr.test.ts

@@ -5,7 +5,7 @@ import { Client } from '../client';
 import { queryOperation, queryResponse } from '../test-utils';
 import { ExchangeIO, Operation, OperationResult } from '../types';
 import { CombinedError, formatDocument } from '../utils';
-import { ssrExchange } from './ssr';
+import { SSRDataStorage, ssrExchange } from './ssr';
 
 let forward: ExchangeIO;
 let exchangeInput;
@@ -52,6 +52,31 @@ it('caches query results correctly', () => {
   });
 });
 
+it('caches query results correctly when storage is provided', () => {
+  output.mockReturnValueOnce(queryResponse);
+
+  const storage: SSRDataStorage = {};
+  const ssr = ssrExchange({ storage });
+  const { source: ops$, next } = input;
+  const exchange = ssr(exchangeInput)(ops$);
+
+  publish(exchange);
+  next(queryOperation);
+
+  const data = ssr.extractData();
+  expect(storage).toEqual(data);
+
+  expect(Object.keys(storage)).toEqual(['' + queryOperation.key]);
+
+  expect(storage).toEqual({
+    [queryOperation.key]: {
+      data: serializedQueryResponse.data,
+      error: undefined,
+      hasNext: false,
+    },
+  });
+});
+
 it('serializes query results quickly', () => {
   const result: OperationResult = {
     ...queryResponse,

packages/core/src/exchanges/ssr.ts

@@ -36,6 +36,10 @@ export interface SSRData {
   [key: string]: SerializedResult;
 }
 
+export interface SSRDataStorage {
+  [key: string]: SerializedResult | null;
+}
+
 /** Options for the `ssrExchange` allowing it to either operate on the server- or client-side. */
 export interface SSRExchangeParams {
   /** Indicates to the {@link SSRExchange} whether it's currently in server-side or client-side mode.
@@ -74,6 +78,11 @@ export interface SSRExchangeParams {
    * not serialize this data by default, unless this flag is set.
    */
   includeExtensions?: boolean;
+
+  /**
+   * If provided, this will be used as underlying storage for the serialized results.
+   */
+  storage?: SSRDataStorage;
 }
 
 /** An `SSRExchange` either in server-side mode, serializing results, or client-side mode, deserializing and replaying results..
@@ -188,7 +197,8 @@ const revalidated = new Set<number>();
 export const ssrExchange = (params: SSRExchangeParams = {}): SSRExchange => {
   const staleWhileRevalidate = !!params.staleWhileRevalidate;
   const includeExtensions = !!params.includeExtensions;
-  const data: Record<string, SerializedResult | null> = {};
+  const data: Record<string, SerializedResult | null> =
+    params.storage !== undefined ? params.storage : {};
 
   // On the client-side, we delete results from the cache as they're resolved
   // this is delayed so that concurrent queries don't delete each other's data