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Feat: Seed remote feature flag controller with default flags #9747

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8ce7cc1
Simplify changes by only introducing default feature flags
Cal-L Aug 4, 2026
97a02b7
Fix lint
Cal-L Aug 4, 2026
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4 changes: 4 additions & 0 deletions packages/remote-feature-flag-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]

### Added

- Add optional `defaultFeatureFlags` constructor option to `RemoteFeatureFlagController` for client-side defaults as the lowest-precedence layer under processed remote flags and local overrides ([#9747](https://github.com/MetaMask/core/pull/9747))

## [5.0.0]

### Added
Expand Down
169 changes: 169 additions & 0 deletions packages/remote-feature-flag-controller/src/remote-feature-flag-controller.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,7 @@ const MOCK_BASE_VERSION = '13.10.0';
* @param options.getMetaMetricsId - Returns metaMetricsId
* @param options.clientVersion - The client version string
* @param options.prevClientVersion - The previous client version string
* @param options.defaultFeatureFlags - Client-side default feature flags
* @returns The controller and the root messenger
*/
function createController(
Expand All @@ -69,6 +70,7 @@ function createController(
getMetaMetricsId: () => string;
clientVersion: string;
prevClientVersion: string;
defaultFeatureFlags: FeatureFlags;
}> = {},
): { controller: RemoteFeatureFlagController; messenger: RootMessenger } {
const { rootMessenger, controllerMessenger } = buildMessenger();
Expand All @@ -83,6 +85,7 @@ function createController(
((): typeof MOCK_METRICS_ID => MOCK_METRICS_ID),
clientVersion: options.clientVersion ?? MOCK_BASE_VERSION,
prevClientVersion: options.prevClientVersion,
defaultFeatureFlags: options.defaultFeatureFlags,
});
return { controller, messenger: rootMessenger };
}
Expand Down Expand Up @@ -1661,6 +1664,172 @@ describe('RemoteFeatureFlagController', () => {
});
});

describe('defaultFeatureFlags', () => {
it('initializes with defaults when no remote or persisted flags exist', () => {
const { controller } = createController({
defaultFeatureFlags: {
defaultFlag: 'defaultValue',
anotherDefault: false,
},
});

expect(controller.state.remoteFeatureFlags).toStrictEqual({
defaultFlag: 'defaultValue',
anotherDefault: false,
});
});

it('applies precedence of override over remote over default', () => {
const { controller } = createController({
state: {
remoteFeatureFlags: {
sharedFlag: 'remoteValue',
remoteOnly: true,
},
rawRemoteFeatureFlags: {
sharedFlag: 'remoteValue',
remoteOnly: true,
},
localOverrides: {
sharedFlag: 'overrideValue',
},
},
defaultFeatureFlags: {
sharedFlag: 'defaultValue',
defaultOnly: 'fromDefaults',
},
});

expect(controller.state.remoteFeatureFlags).toStrictEqual({
sharedFlag: 'overrideValue',
remoteOnly: true,
defaultOnly: 'fromDefaults',
});
});

it('keeps defaults for flags absent from a remote fetch', async () => {
const clientConfigApiService = buildClientConfigApiService({
remoteFeatureFlags: { remoteFlag: 'fromServer' },
});
const { controller, messenger } = createController({
clientConfigApiService,
defaultFeatureFlags: {
defaultOnly: 'fromDefaults',
remoteFlag: 'defaultRemote',
},
});

await messenger.call(
'RemoteFeatureFlagController:updateRemoteFeatureFlags',
);

expect(controller.state.remoteFeatureFlags).toStrictEqual({
defaultOnly: 'fromDefaults',
remoteFlag: 'fromServer',
});
});

it('restores default when removing an override with no remote value', () => {
const { controller, messenger } = createController({
defaultFeatureFlags: {
defaultFlag: 'defaultValue',
},
});

messenger.call(
'RemoteFeatureFlagController:setFlagOverride',
'defaultFlag',
'overrideValue',
);
messenger.call(
'RemoteFeatureFlagController:removeFlagOverride',
'defaultFlag',
);

expect(controller.state.remoteFeatureFlags).toStrictEqual({
defaultFlag: 'defaultValue',
});
expect(controller.state.localOverrides).toStrictEqual({});
});

it('strips default-only keys from the processed layer on init', () => {
const { controller, messenger } = createController({
state: {
// Stale baked-in default from a previous session
remoteFeatureFlags: {
defaultOnly: 'staleDefault',
remoteFlag: 'remoteValue',
},
rawRemoteFeatureFlags: {
remoteFlag: 'remoteValue',
},
},
defaultFeatureFlags: {
defaultOnly: 'currentDefault',
},
});

expect(controller.state.remoteFeatureFlags).toStrictEqual({
defaultOnly: 'currentDefault',
remoteFlag: 'remoteValue',
});

messenger.call('RemoteFeatureFlagController:clearAllFlagOverrides');

expect(controller.state.remoteFeatureFlags).toStrictEqual({
defaultOnly: 'currentDefault',
remoteFlag: 'remoteValue',
});
});

it('treats undefined rawRemoteFeatureFlags as empty when stripping defaults on init', () => {
const { controller } = createController({
state: {
remoteFeatureFlags: {
defaultOnly: 'staleDefault',
remoteFlag: 'remoteValue',
},
rawRemoteFeatureFlags: undefined,
},
defaultFeatureFlags: {
defaultOnly: 'currentDefault',
},
});

// defaultOnly is stripped from processed (not in raw) and replaced by
// the current default; remoteFlag is kept because it is not a default key.
expect(controller.state.remoteFeatureFlags).toStrictEqual({
defaultOnly: 'currentDefault',
remoteFlag: 'remoteValue',
});
});

it('treats undefined localOverrides as empty when updating the cache', async () => {
const clientConfigApiService = buildClientConfigApiService({
remoteFeatureFlags: { remoteFlag: 'fromServer' },
});
const { controller, messenger } = createController({
clientConfigApiService,
state: {
localOverrides: undefined,
},
defaultFeatureFlags: {
defaultOnly: 'fromDefaults',
},
});

await messenger.call(
'RemoteFeatureFlagController:updateRemoteFeatureFlags',
);

expect(controller.state.localOverrides).toBeUndefined();
expect(controller.state.remoteFeatureFlags).toStrictEqual({
defaultOnly: 'fromDefaults',
remoteFlag: 'fromServer',
});
});
});

describe('threshold cache cleanup', () => {
it('removes stale threshold cache entries when flags are removed from server', async () => {
jest.useRealTimers();
Expand Down
89 changes: 60 additions & 29 deletions packages/remote-feature-flag-controller/src/remote-feature-flag-controller.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -214,6 +214,8 @@ export class RemoteFeatureFlagController extends BaseController<

readonly #clientVersion: SemVerVersion;

readonly #defaultFeatureFlags: FeatureFlags;

#processedRemoteFeatureFlags: FeatureFlags = {};

/**
Expand All @@ -228,6 +230,7 @@ export class RemoteFeatureFlagController extends BaseController<
* @param options.getMetaMetricsId - Returns metaMetricsId.
* @param options.clientVersion - The current client version for version-based feature flag filtering. Must be a valid 3-part SemVer version string.
* @param options.prevClientVersion - The previous client version for feature flag cache invalidation.
* @param options.defaultFeatureFlags - Client-side default feature flags used as the lowest-precedence layer under processed remote flags and local overrides. Not persisted.

@DDDDDanica DDDDDanica Aug 4, 2026

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Question: what is the different between rawRemoteFeatureFlags and defaultFeatureFlags?

*/
constructor({
messenger,
Expand All @@ -238,6 +241,7 @@ export class RemoteFeatureFlagController extends BaseController<
getMetaMetricsId,
clientVersion,
prevClientVersion,
defaultFeatureFlags = {},

@Cal-L Cal-L Aug 4, 2026

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Ability for platforms to provide feature flag defaults

}: {
messenger: RemoteFeatureFlagControllerMessenger;
state?: Partial<RemoteFeatureFlagControllerState>;
Expand All @@ -247,6 +251,7 @@ export class RemoteFeatureFlagController extends BaseController<
disabled?: boolean;
clientVersion: string;
prevClientVersion?: string;
defaultFeatureFlags?: FeatureFlags;
}) {
if (!isValidSemVerVersion(clientVersion)) {
throw new Error(
Expand All @@ -264,6 +269,23 @@ export class RemoteFeatureFlagController extends BaseController<
prevClientVersion !== clientVersion;

const localOverrides = initialState.localOverrides ?? {};
const rawRemoteFeatureFlags = initialState.rawRemoteFeatureFlags ?? {};

// Rebuild the processed remote layer from last session's effective flags by
// stripping local overrides and default-only keys (absent from raw).
const processedRemoteFeatureFlags = {
...initialState.remoteFeatureFlags,
};
for (const [flagName, overrideValue] of Object.entries(localOverrides)) {
if (processedRemoteFeatureFlags[flagName] === overrideValue) {
delete processedRemoteFeatureFlags[flagName];
}
}
for (const flagName of Object.keys(defaultFeatureFlags)) {
if (rawRemoteFeatureFlags[flagName] === undefined) {
delete processedRemoteFeatureFlags[flagName];
}
}

super({
name: controllerName,
Expand All @@ -272,7 +294,8 @@ export class RemoteFeatureFlagController extends BaseController<
state: {
...initialState,
remoteFeatureFlags: {
...initialState.remoteFeatureFlags,
...defaultFeatureFlags,
...processedRemoteFeatureFlags,
...localOverrides,
},
cacheTimestamp: hasClientVersionChanged
Expand All @@ -281,15 +304,8 @@ export class RemoteFeatureFlagController extends BaseController<
},
});

this.#processedRemoteFeatureFlags = {
...initialState.remoteFeatureFlags,
};
for (const [flagName, overrideValue] of Object.entries(localOverrides)) {
if (this.#processedRemoteFeatureFlags[flagName] === overrideValue) {
delete this.#processedRemoteFeatureFlags[flagName];
}
}

this.#defaultFeatureFlags = defaultFeatureFlags;
this.#processedRemoteFeatureFlags = processedRemoteFeatureFlags;
this.#fetchInterval = fetchInterval;
this.#disabled = disabled;
this.#clientConfigApiService = clientConfigApiService;
Expand All @@ -302,6 +318,25 @@ export class RemoteFeatureFlagController extends BaseController<
);
}

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/**
* Computes effective feature flags with precedence:
* defaults < processed remote < local overrides.
*
* @param processedRemote - The processed remote feature flags.
* @param localOverrides - Local overrides. Defaults to current state overrides.
* @returns The effective feature flags.
*/
#getEffectiveFeatureFlags(
processedRemote: FeatureFlags,
localOverrides: FeatureFlags = this.state.localOverrides ?? {},
): FeatureFlags {
return {
...this.#defaultFeatureFlags,
...processedRemote,
...localOverrides,
};
}

/**
* Checks if the cached feature flags are expired based on the fetch interval.
*
Expand Down Expand Up @@ -388,10 +423,9 @@ export class RemoteFeatureFlagController extends BaseController<
this.update(() => {
return {
...this.state,
remoteFeatureFlags: {
...redactedProcessedFlags,
...this.state.localOverrides,
},
remoteFeatureFlags: this.#getEffectiveFeatureFlags(
redactedProcessedFlags,
),
rawRemoteFeatureFlags: redactMetaMetricsIds(remoteFeatureFlags),
cacheTimestamp: Date.now(),
thresholdCache: updatedThresholdCache,
Expand Down Expand Up @@ -543,10 +577,10 @@ export class RemoteFeatureFlagController extends BaseController<
return {
...this.state,
localOverrides,
remoteFeatureFlags: {
...this.state.remoteFeatureFlags,
[flagName]: value,
},
remoteFeatureFlags: this.#getEffectiveFeatureFlags(
this.#processedRemoteFeatureFlags,
localOverrides,
),
};
});
}
Expand All @@ -560,20 +594,14 @@ export class RemoteFeatureFlagController extends BaseController<
const newLocalOverrides = { ...this.state.localOverrides };
delete newLocalOverrides[flagName];

const remoteFeatureFlags = { ...this.state.remoteFeatureFlags };
const processedValue = this.#processedRemoteFeatureFlags[flagName];

if (processedValue === undefined) {
delete remoteFeatureFlags[flagName];
} else {
remoteFeatureFlags[flagName] = processedValue;
}

this.update(() => {
return {
...this.state,
localOverrides: newLocalOverrides,
remoteFeatureFlags,
remoteFeatureFlags: this.#getEffectiveFeatureFlags(
this.#processedRemoteFeatureFlags,
newLocalOverrides,
),
};
});
}
Expand All @@ -586,7 +614,10 @@ export class RemoteFeatureFlagController extends BaseController<
return {
...this.state,
localOverrides: {},
remoteFeatureFlags: { ...this.#processedRemoteFeatureFlags },
remoteFeatureFlags: this.#getEffectiveFeatureFlags(
this.#processedRemoteFeatureFlags,
{},
),
};
});
}
Expand Down
4 changes: 4 additions & 0 deletions packages/wallet/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]

### Added

- Add optional `instanceOptions.remoteFeatureFlagController.defaultFeatureFlags` to pass client-side default feature flags through to `RemoteFeatureFlagController` ([#9747](https://github.com/MetaMask/core/pull/9747))

### Changed

- Bump `@metamask/transaction-controller` from `^69.4.0` to `^69.5.0` ([#9780](https://github.com/MetaMask/core/pull/9780))
Expand Down
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