refactor: Decompose simulation, add tests by askov · Pull Request #928 · solana-foundation/explorer

askov · 2026-04-08T09:19:39Z

Description

Extract compute-unit FSD entity — moves CU schedule logic, default CU values, instruction log formatting, and the CUProfilingCard component out of utils/ and features/cu-profiling/ into
entities/compute-unit/, with a clean public API via barrel export
Decompose useSimulation hook — breaks the monolithic 300+ line hook into focused, pure library functions (simulateTransaction, buildTokenBalances, computeSolBalanceChanges, getMintDecimals,
resolveAddressLookupTables) that are independently testable and easier to reason about
Add comprehensive test coverage — new test suites for all extracted lib functions plus the useSimulation hook and SolBalanceChangesCard Storybook stories

Type of change

Other (please describe): Refactoring + tests

Testing

Regression targets

Related Issues

Closes HOO-410

Checklist

My code follows the project's style guidelines
I have added tests that prove my fix/feature works
All tests pass locally and in CI
I have run build:info script to update build information
CI/CD checks pass

vercel · 2026-04-08T09:19:45Z

@askov is attempting to deploy a commit to the Solana Foundation Team on Vercel.

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greptile-apps · 2026-04-08T09:23:19Z

Greptile Summary

This PR decomposes the monolithic useSimulation hook (300+ lines) into focused, independently-testable library functions (simulateTransaction, buildTokenBalances, computeSolBalanceChanges, getMintDecimals, resolveAddressLookupTables), migrates CU-profiling logic into a new entities/compute-unit/ FSD entity, and adds comprehensive test coverage across all extracted units. Both previously-flagged issues (ALT accounts silently dropped from balance tracking, fingerprint cache key not including ALT configuration) are correctly resolved.

Confidence Score: 5/5

This PR is safe to merge — all previously-flagged correctness issues are resolved and no new P0/P1 issues were found.

Both prior blocking concerns (ALT-resolved accounts silently dropped, cache key missing ALT configuration) are definitively fixed. The new resolveAddressLookupTables also silently fixed a key-index alignment bug from the old filter-then-map pattern, and the test suite is comprehensive across all extracted units. No remaining findings rise above P2.

No files require special attention.

Vulnerabilities

No security concerns identified. The refactoring does not alter authentication boundaries, and all external data (RPC responses, base64-encoded account buffers) is validated before use (size checks, program-owner checks). Token amounts are handled via bigint to avoid precision loss.

Important Files Changed

Filename	Overview
app/features/instruction-simulation/lib/simulate-transaction.ts	New pure async function orchestrating RPC calls and result interpretation; now correctly uses keySegments().flat() to include ALT-resolved accounts, fixing the previously-flagged silent data loss.
app/features/instruction-simulation/model/use-simulation.ts	Refactored to use useSWRMutation; fingerprint now serializes the full message (fixing the ALT cache-key collision); clean discriminated-union state type replaces scattered useState calls.
app/features/instruction-simulation/lib/build-token-balances.ts	Extracted token balance builder; uses readU64LE returning bigint instead of Number(...), fixing precision loss for amounts > Number.MAX_SAFE_INTEGER. Token-2022 discriminator byte correctly handled.
app/features/instruction-simulation/lib/resolve-address-lookup-tables.ts	New helper; also fixes a subtle index-alignment bug from the old code where filtering null accounts before mapping caused key mismatches for missing ALTs.
app/features/instruction-simulation/ui/SimulationCard.tsx	Cleanly decomposed into distinct status branches using SimulationCardShell; introduces generateTokenBalanceRows at the UI layer where it belongs. Token balance and SOL balance cards are correctly gated on succeeded.
app/features/instruction-simulation/lib/tests/simulate-transaction.spec.ts	456-line test suite covering happy path, error branches, ALT resolution, token balance parsing, and large-amount precision.
app/entities/compute-unit/index.ts	New barrel export for the compute-unit FSD entity; clean public API surface.
app/features/instruction-simulation/lib/get-mint-decimals.ts	Correctly distinguishes mint vs token-account buffers for both base spl-token and Token-2022 extended accounts using the type discriminator at offset 165.

_{Reviews (3): Last reviewed commit: "fix: show simulation error when RPC retu..." | Re-trigger Greptile}

askov · 2026-04-08T11:22:07Z

@greptile-apps please review

vercel · 2026-04-08T11:22:40Z

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Project	Deployment	Actions	Updated (UTC)
explorer	Ready	Preview, Comment	Apr 13, 2026 9:11am

askov · 2026-04-08T11:36:37Z

@greptile-apps please review

rogaldh · 2026-04-10T18:49:09Z

+
+const KEY_A = new PublicKey('5ZiE3vAkrdXBgyFL7KqG3RoEGBws8CjY8AsGq1MuR5My');
+const KEY_B = new PublicKey('EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v');
+const KEY_C = new PublicKey('So11111111111111111111111111111111111111112');


nit: I'd prefer using Keypair.generate().pubkey here to create a key if we just need a key. Otherwise, it seems that we need a specific key

Replaced all the hardcoded keys where possible

rogaldh · 2026-04-10T18:53:12Z

+const USDC_MINT = 'EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v';
+
+/** Real ALT account data from mainnet. Addresses: ADDR_3ZK, ADDR_SQDS, ADDR_BGUMA */
+const ALT_FIXTURE_3_ADDRS =


I'd move these into app/fixtures directory as they are for real ALTs

rogaldh · 2026-04-10T19:26:27Z

+
+import { MINT_SIZE, TOKEN_ACCOUNT_SIZE } from '../lib/token-layout';
+
+export const TOKEN_PROGRAM = 'TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA';


For token programs, it is better to use solana-program/token & token2022

rogaldh · 2026-04-10T19:27:50Z

+export const SYSTEM_PROGRAM = '11111111111111111111111111111111';
+
+export const USDC_MINT = new PublicKey('EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v');
+export const WSOL_MINT = new PublicKey('So11111111111111111111111111111111111111112');


WSOL is present at the project as NATIVE_MINT. USDC_MINT might be moved to app/__fixtures or __mocks

Replaced NATIVE_MINT and moved USDC_MINT to shared, as it's not a fixture, and we have several of them hardcoded in different files.

rogaldh · 2026-04-10T19:29:35Z

+
+/** String comparison for RPC responses where owner is a base58 string, not a PublicKey */
+export function isTokenProgramBase58(owner: string): boolean {
+    return owner === TOKEN_PROGRAM_BASE58 || owner === TOKEN_2022_PROGRAM_BASE58;


We have a similar helper at app/shared/model/token-program.ts

Moved the helper to the shared model

rogaldh · 2026-04-10T19:44:54Z

+export const MIN_MINT_ACCOUNT_BUFFER_LENGTH = MINT_SIZE;
+
+/** Base SPL token account size (bytes) */
+export const TOKEN_ACCOUNT_SIZE = 165;


@solana-program/token client has methods to get sizes for mint size and TA size

Thanks, replaced

rogaldh · 2026-04-10T19:48:33Z

+ * Token-2022 account type discriminator values.
+ * The discriminator byte sits at offset `TOKEN_ACCOUNT_SIZE` (165).
+ */
+export const ACCOUNT_TYPE_MINT = 1;


solana-program/token also has account types in it

I mean that we could reuse already existing logic within the client to make better refactoring

Imported everything I could find

rogaldh

Except these ^ LGTM

rogaldh · 2026-04-10T20:51:18Z

+import type { SimulationResult } from '../../lib/simulate-transaction';
+import type { SimulationState } from '../use-simulation';
+
+const MOCK_URL = 'https://api.devnet.solana.com';


Let's use 'https://devnet.rpc.address', maybe, to distinguish it from a real address unless the types require it to look like a devnet address

rogaldh · 2026-04-10T20:53:30Z

+        expect(typeof getSimulate(result.current)).toBe('function');
+    });
+
+    it('should transition to done with result on success', async () => {


I may be missing something, but it looks like we need to construct some real transaction data (Message), which would have tolen and sol changes to test that buffer layouts work

This is already covered by unit tests

…ntity

…isions

greptile-apps bot reviewed Apr 8, 2026

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Comment thread app/features/instruction-simulation/lib/simulate-transaction.ts Outdated

Comment thread app/features/instruction-simulation/model/use-simulation.ts Outdated

vercel bot deployed to Preview April 8, 2026 11:28 View deployment

vercel bot deployed to Preview April 8, 2026 11:39 View deployment

askov force-pushed the refactor/decompose-simulation-extract-cu-entity branch from 6dfde53 to eab0de7 Compare April 9, 2026 06:44

vercel bot deployed to Preview April 9, 2026 06:51 View deployment

rogaldh reviewed Apr 10, 2026

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rogaldh approved these changes Apr 10, 2026

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rogaldh reviewed Apr 10, 2026

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askov added 6 commits April 13, 2026 14:12

refactor: decompose instruction simulation and extract compute-unit e…

5af1e22

…ntity

fix(test): correct error expectation in simulate-transaction spec

a196f2e

chore: run build:info

020c50e

fix: include ALT keys in simulation cache fingerprint to prevent coll…

4cf50f4

…isions

fix: include ALT-resolved accounts in simulation balance tracking

daf48dd

fix: show simulation error when RPC returns empty logs

c86a616

askov force-pushed the refactor/decompose-simulation-extract-cu-entity branch from eab0de7 to c86a616 Compare April 13, 2026 07:12

fix: address review feedback

ff842bf

vercel bot deployed to Preview April 13, 2026 09:11 View deployment


		import { MINT_SIZE, TOKEN_ACCOUNT_SIZE } from '../lib/token-layout';

		export const TOKEN_PROGRAM = 'TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA';

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Description

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Testing

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Greptile Summary

Confidence Score: 5/5

Vulnerabilities

Important Files Changed

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askov commented Apr 8, 2026

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