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fix: shield: Make start and stop idempotent #6817

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Merged
merged 3 commits into from
Oct 10, 2025
Merged

fix: shield: Make start and stop idempotent #6817

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b87ea2f
Make start and stop idempotent
matthiasgeihs Oct 10, 2025
be660f2
Update CHANGELOG
matthiasgeihs Oct 10, 2025
457c056
Merge branch 'main' into mg/shield/make-start-idempotent
matthiasgeihs Oct 10, 2025
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4 changes: 4 additions & 0 deletions packages/shield-controller/CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased]

### Changed

- Make start and stop idempotent ([#6817](https://github.com/MetaMask/core/pull/6817))

## [0.3.1]

### Changed
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24 changes: 18 additions & 6 deletions packages/shield-controller/src/ShieldController.test.ts
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Expand Up @@ -57,12 +57,24 @@ describe('ShieldController', () => {
it('should trigger checkCoverage when a new transaction is added', async () => {
const { baseMessenger, backend } = setup();
const txMeta = generateMockTxMeta();
const coverageResultReceived = new Promise<void>((resolve) => {
baseMessenger.subscribe(
'ShieldController:coverageResultReceived',
(_coverageResult) => resolve(),
);
});
const coverageResultReceived = setupCoverageResultReceived(baseMessenger);
baseMessenger.publish(
'TransactionController:stateChange',
{ transactions: [txMeta] } as TransactionControllerState,
undefined as never,
);
expect(await coverageResultReceived).toBeUndefined();
expect(backend.checkCoverage).toHaveBeenCalledWith({ txMeta });
});

it('should tolerate calling start and stop multiple times', async () => {
const { backend, baseMessenger, controller } = setup();
controller.stop();
controller.stop();
controller.start();
controller.start();
const txMeta = generateMockTxMeta();
const coverageResultReceived = setupCoverageResultReceived(baseMessenger);
baseMessenger.publish(
'TransactionController:stateChange',
{ transactions: [txMeta] } as TransactionControllerState,
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13 changes: 13 additions & 0 deletions packages/shield-controller/src/ShieldController.ts
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Expand Up @@ -152,6 +152,8 @@ export class ShieldController extends BaseController<
previousSignatureRequests: Record<string, SignatureRequest> | undefined,
) => void;

#started: boolean;

constructor(options: ShieldControllerOptions) {
const {
messenger,
Expand All @@ -177,9 +179,15 @@ export class ShieldController extends BaseController<
this.#handleTransactionControllerStateChange.bind(this);
this.#signatureControllerStateChangeHandler =
this.#handleSignatureControllerStateChange.bind(this);
this.#started = false;
}

start() {
if (this.#started) {
return;
}
this.#started = true;

this.messagingSystem.subscribe(
'TransactionController:stateChange',
this.#transactionControllerStateChangeHandler,
Expand All @@ -194,6 +202,11 @@ export class ShieldController extends BaseController<
}

stop() {
if (!this.#started) {
return;
}
this.#started = false;

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Bug: State Update Timing Causes Subscription Inconsistency

The #started flag is updated before subscription/unsubscription operations. If these operations fail, the controller's #started state won't reflect its actual subscription status. This inconsistency can cause start() or stop() to return early, leaving the controller partially subscribed or still receiving events.

Fix in Cursor Fix in Web

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Good point. We might need to fix this in a later version.

this.messagingSystem.unsubscribe(
'TransactionController:stateChange',
this.#transactionControllerStateChangeHandler,
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