fix(idl): dedupe Anchor IDL fetches during Suspense retries

app/entities/idl/model/__tests__/use-idl-from-anchor-program-seed.test.ts

@@ -0,0 +1,66 @@
+import { Program } from '@coral-xyz/anchor';
+import { PublicKey } from '@solana/web3.js';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+
+import { Cluster } from '@/app/utils/cluster';
+
+import { resetCacheForTesting, useIdlFromAnchorProgramSeed } from '../use-idl-from-anchor-program-seed';
+
+describe('useIdlFromAnchorProgramSeed', () => {
+    const url = 'https://any.rpc.address';
+
+    afterEach(() => {
+        vi.unstubAllGlobals();
+        vi.restoreAllMocks();
+        resetCacheForTesting();
+    });
+
+    it('should not fire duplicate /api/anchor requests for the same key while the request is in flight', () => {
+        const fetchMock = vi.fn(() => new Promise<Response>(() => {}));
+        vi.stubGlobal('fetch', fetchMock);
+
+        const programAddress = PublicKey.unique().toBase58();
+
+        let firstThrown: unknown;
+        let secondThrown: unknown;
+
+        try {
+            useIdlFromAnchorProgramSeed(programAddress, url, Cluster.MainnetBeta);
+        } catch (e) {
+            firstThrown = e;
+        }
+        try {
+            useIdlFromAnchorProgramSeed(programAddress, url, Cluster.MainnetBeta);
+        } catch (e) {
+            secondThrown = e;
+        }
+
+        expect(firstThrown).toBeInstanceOf(Promise);
+        expect(secondThrown).toBe(firstThrown);
+        expect(fetchMock).toHaveBeenCalledTimes(1);
+    });
+
+    it('should not call Program.fetchIdl twice for the same key while the request is in flight on a Custom cluster', () => {
+        const fetchIdlSpy = vi.spyOn(Program, 'fetchIdl').mockReturnValue(new Promise(() => {}));
+
+        const programAddress = PublicKey.unique().toBase58();
+
+        let firstThrown: unknown;
+        let secondThrown: unknown;
+
+        try {
+            useIdlFromAnchorProgramSeed(programAddress, url, Cluster.Custom);
+        } catch (e) {
+            firstThrown = e;
+        }
+        try {
+            useIdlFromAnchorProgramSeed(programAddress, url, Cluster.Custom);
+        } catch (e) {
+            secondThrown = e;
+        }
+
+        expect(firstThrown).toBeInstanceOf(Promise);
+        expect(secondThrown).toBe(firstThrown);
+        expect(fetchIdlSpy).toHaveBeenCalledTimes(1);
+    });
+});

app/entities/idl/model/use-idl-from-anchor-program-seed.ts

@@ -15,6 +15,16 @@ export function getProvider(url: string) {
     return new AnchorProvider(new Connection(url), new NodeWallet(Keypair.generate()), {});
 }
 
+function recordInFlight(key: string, promise: Promise<void>) {
+    cachedAnchorProgramPromises[key] = { __type: 'promise', promise };
+}
+
+export function resetCacheForTesting() {
+    for (const k of Object.keys(cachedAnchorProgramPromises)) {
+        delete cachedAnchorProgramPromises[k];
+    }
+}
+
 export function useIdlFromAnchorProgramSeed(programAddress: string, url: string, cluster?: Cluster): Idl | null {
     const key = `${programAddress}-${url}`;
     const cacheEntry = cachedAnchorProgramPromises[key];
@@ -43,6 +53,7 @@ export function useIdlFromAnchorProgramSeed(programAddress: string, url: string,
                 .catch(_ => {
                     cachedAnchorProgramPromises[key] = { __type: 'result', result: null };
                 });
+            recordInFlight(key, promise);
         } else {
             const programId = new PublicKey(programAddress);
             promise = Program.fetchIdl<Idl>(programId, getProvider(url))
@@ -59,10 +70,7 @@ export function useIdlFromAnchorProgramSeed(programAddress: string, url: string,
                 .catch(_ => {
                     cachedAnchorProgramPromises[key] = { __type: 'result', result: null };
                 });
-            cachedAnchorProgramPromises[key] = {
-                __type: 'promise',
-                promise,
-            };
+            recordInFlight(key, promise);
         }
         throw promise;
     } else if (cacheEntry.__type === 'promise') {