feat(persisted): Allow nullish hashes for skipping persisted logic (#…

…3324)

.changeset/seven-adults-fix.md

@@ -0,0 +1,5 @@
+---
+'@urql/exchange-persisted': minor
+---
+
+Allow persisted query logic to be skipped by the `persistedExchange` if the passed `generateHash` function resolves to a nullish value. This allows (A)PQ to be selectively disabled for individual operations.

exchanges/persisted/src/persistedExchange.test.ts

@@ -119,6 +119,27 @@ it('retries query persisted query resulted in unsupported', async () => {
   expect(operations[2].extensions).toEqual(undefined);
 });
 
+it('skips operation when generateHash returns a nullish value', async () => {
+  const { result, operations, exchangeArgs } = makeExchangeArgs();
+
+  result.mockImplementationOnce(operation => ({
+    ...queryResponse,
+    operation,
+    data: null,
+  }));
+
+  const res = await pipe(
+    fromValue(queryOperation),
+    persistedExchange({ generateHash: async () => null })(exchangeArgs),
+    take(1),
+    toPromise
+  );
+
+  expect(res.operation.context.persistAttempt).toBe(true);
+  expect(operations.length).toBe(1);
+  expect(operations[0]).not.toHaveProperty('extensions.persistedQuery');
+});
+
 it.each([true, 'force', 'within-url-limit'] as const)(
   'sets `context.preferGetMethod` to %s when `options.preferGetForPersistedQueries` is %s',
   async preferGetMethodValue => {

exchanges/persisted/src/persistedExchange.ts

@@ -68,14 +68,18 @@ export interface PersistedExchangeOptions {
    * hashes at compile-time, or need to use a custom SHA-256 function,
    * you may pass one here.
    *
+   * If `generateHash` returns either `null` or `undefined`, the
+   * operation will not be treated as a persisted operation, which
+   * essentially skips this exchange’s logic for a given operation.
+   *
    * Hint: The default SHA-256 function uses the WebCrypto API. This
    * API is unavailable on React Native, which may require you to
    * pass a custom function here.
    */
   generateHash?(
     query: string,
     document: TypedDocumentNode<any, any>
-  ): Promise<string>;
+  ): Promise<string | undefined | null>;
   /** Enables persisted queries to be used for mutations.
    *
    * @remarks