Memoize selectCustomNetworkConfigurationsByCaipChainId filter result

Start with app/selectors/networkController.ts:274 and inspect how selectCustomNetworkConfigurationsByCaipChainId derives its result. Then read app/selectors/networkController.test.ts:177 and add coverage for referential stability across equal-content states. Done means the selector preserves the array reference when contents are unchanged and the selector tests pass.

Performance audit finding · Severity: Medium · Effort: Easy · Fix risk: Simple · Test safety net: Partial
Owner: @MetaMask/mobile-core-ux (suggested)
File: app/selectors/networkController.ts:274

What is this about?

selectCustomNetworkConfigurationsByCaipChainId is a plain createSelector whose result function returns Object.values(...).filter(...), building a new array every recompute. Its input selectNetworkConfigurationsByCaipChainId is a plain createSelector that builds a fresh object (via getNetworkConfigurationsByCaipChainId spreads) whenever either network slice changes, so this selector reruns and yields a new array on any network-slice mutation.

Why it matters

Custom network lists feed network management/picker UI. A new array reference forces consumers to re-render even when the custom networks are unchanged.

Scenario

N/A — see Technical Details.

Design

N/A — internal performance change; no UI/design impact.

Technical Details

Evidence

app/selectors/networkController.ts:274

export const selectCustomNetworkConfigurationsByCaipChainId = createSelector(
  selectNetworkConfigurationsByCaipChainId,
  (networkConfigurationsByChainId) =>
    Object.values(networkConfigurationsByChainId).filter(
      (networkConfiguration) =>
        (networkConfiguration.chainId.startsWith('0x') &&
          !POPULAR_NETWORK_CHAIN_IDS.has(networkConfiguration.chainId as Hex)) ||
        NON_EVM_TESTNET_IDS.includes(networkConfiguration.caipChainId),
    ),
);

Fix

Switch to createDeepEqualSelector so the filtered array is referentially stable when contents are unchanged.

Threat Modeling Framework

N/A — performance-only change; behavior is preserved, no new data flow / trust boundary / attack surface.

Acceptance Criteria

• app/selectors/networkController.test.ts:177 asserts values but not referential stability. Add a test asserting toBe across two equal-content states. Profiler: confirm network-management consumers stop re-rendering on unrelated network-state changes.

References

• File: app/selectors/networkController.ts:274
• Source: MetaMask Mobile performance audit — finding selector-custom-network-configs-by-caip
• Owner (CODEOWNERS / best-effort): @MetaMask/mobile-core-ux (suggested)
• Status: UNVALIDATED