perf: Filter out certain Snaps fields in Engine redux slice

app/core/redux/slices/engine/engineReducer.test.tsx

@@ -52,4 +52,51 @@ describe('engineReducer', () => {
       AccountTrackerController: Engine.state[key],
     });
   });
+
+  it('should filter out unnecesary Snaps state', () => {
+    const reduxInitialState = {
+      backgroundState: {
+        SnapController: {
+          snaps: {},
+          snapStates: {},
+          unencryptedSnapStates: {},
+        },
+      },
+    };
+
+    const key = 'SnapController';
+    // changing the mock version to suit this test manually due to our current global mock
+    // TODO: Replace "any" with type
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    (Engine as any).state = {
+      SnapController: {
+      snaps: {
+        'npm:@metamask/bip32-example-snap': {
+          id: 'npm:@metamask/bip32-example-snap',
+          sourceCode: 'foo bar',
+        },
+      },
+      snapStates: {},
+      unencryptedSnapStates: {
+        'npm:@metamask-bip32-example-snap': JSON.stringify({ foo: 'bar' }),
+      },
+    }
+    };
+    const { backgroundState } = engineReducer(
+      reduxInitialState,
+      updateBgState({ key }),
+    );
+    expect(backgroundState).toEqual({
+      ...reduxInitialState.backgroundState,
+      SnapController: {
+        snaps: {
+          'npm:@metamask/bip32-example-snap': {
+            id: 'npm:@metamask/bip32-example-snap',
+          },
+        },
+        snapStates: {},
+        unencryptedSnapStates: {},
+      }
+    });
+  });
 });

app/core/redux/slices/engine/index.ts

@@ -1,6 +1,9 @@
 import { cloneDeep } from 'lodash';
 import Engine from '../../../Engine';
 import { createAction, PayloadAction } from '@reduxjs/toolkit';
+///: BEGIN:ONLY_INCLUDE_IF(preinstalled-snaps,external-snaps)
+import { PersistedSnap } from '@metamask/snaps-utils';
+///: END:ONLY_INCLUDE_IF
 
 const initialState = {
   // TODO: Replace "any" with type
@@ -18,6 +21,34 @@ export const updateBgState = createAction('UPDATE_BG_STATE', (key) => ({
   payload: key,
 }));
 
+/**
+ * Filters out state values that we do not want to include in the Redux store.
+ *
+ * @param key The state key, which should also be the controller name.
+ * @param value The state blob for a controller.
+ * @returns A filtered state blob for a given controller.
+ */
+function filterState(key: string, value: any) {
+  ///: BEGIN:ONLY_INCLUDE_IF(preinstalled-snaps,external-snaps)
+  if (key === 'SnapController') {
+    return {
+      snapStates: {},
+      unencryptedSnapStates: {},
+      snaps: Object.values(value.snaps as Record<string, PersistedSnap>).reduce<
+        Record<string, Omit<PersistedSnap, 'sourceCode'>>
+      >((acc, snap) => {
+        // eslint-disable-next-line no-unused-vars
+        const { sourceCode, auxiliaryFiles, ...rest } = snap;
+        acc[snap.id] = rest;
+        return acc;
+      }, {}),
+    };
+  }
+  ///: END:ONLY_INCLUDE_IF
+
+  return value;
+}
+
 // TODO: Replace "any" with type
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 export const counter: any = {};
@@ -46,10 +77,12 @@ const engineReducer = (
         // - Deep comparison selectors do not fire since the cached objects are references to the original
         //  state object which has been mutated.
         // This is resolved by doing a deep clone in this scenario to force an entirely new object.
-        newState.backgroundState[action.payload?.key] =
+        newState.backgroundState[action.payload?.key] = filterState(
+          action.payload.key,
           legacyControllers.includes(action.payload.key)
             ? cloneDeep(newControllerState)
-            : newControllerState;
+            : newControllerState,
+        );
       }
 
       return newState;

app/selectors/snaps/snapController.ts

@@ -3,7 +3,6 @@ import { RootState } from '../../reducers';
 import { createDeepEqualSelector } from '../util';
 import { getLocalizedSnapManifest } from '@metamask/snaps-utils';
 
-// TODO: Filter out huge values
 export const selectSnapControllerState = (state: RootState) =>
   state.engine.backgroundState.SnapController;