fix: skip no-op AssetsController state assignments

packages/assets-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Skip `#updateState` assignments whose metadata, balances, or prices are deep-equal to current state so Immer does not publish no-op `stateChange` events ([#10223](https://github.com/MetaMask/core/pull/10223))
+
 ## [15.1.0]
 
 ### Changed

packages/assets-controller/src/AssetsController.test.ts

@@ -2208,6 +2208,91 @@ describe('AssetsController', () => {
       });
     });
 
+    describe('when the response repeats data already in state', () => {
+      const repeatedMetadata: FungibleAssetMetadata = {
+        type: 'erc20',
+        symbol: 'USDC',
+        name: 'USD Coin',
+        decimals: 6,
+      };
+      const repeatedPrice = {
+        assetPriceType: 'fungible',
+        price: 1,
+        usdPrice: 1,
+        lastUpdated: 1_700_000_000_000,
+      } as const;
+      const repeatedState: Partial<AssetsControllerState> = {
+        assetsInfo: { [MOCK_ASSET_ID]: repeatedMetadata },
+        assetsBalance: {
+          [MOCK_ACCOUNT_ID]: {
+            [MOCK_ASSET_ID]: { amount: '1000000' },
+            [MOCK_NATIVE_ASSET_ID]: { amount: '0' },
+          },
+        },
+        assetsPrice: { [MOCK_ASSET_ID]: repeatedPrice },
+      };
+      const repeatedResponse: DataResponse = {
+        assetsInfo: { [MOCK_ASSET_ID]: { ...repeatedMetadata } },
+        assetsBalance: {
+          [MOCK_ACCOUNT_ID]: {
+            [MOCK_ASSET_ID]: { amount: '1000000' },
+            [MOCK_NATIVE_ASSET_ID]: { amount: '0' },
+          },
+        },
+        assetsPrice: { [MOCK_ASSET_ID]: { ...repeatedPrice } },
+      };
+
+      it('does not publish stateChange', async () => {
+        await withController(
+          { state: repeatedState, isBasicFunctionality: () => false },
+          async ({ controller, messenger }) => {
+            await flushPromises();
+            const stateChangeListener = jest.fn();
+            messenger.subscribe(
+              'AssetsController:stateChange',
+              stateChangeListener,
+            );
+
+            await controller.handleAssetsUpdate(repeatedResponse, 'TestSource');
+
+            expect(stateChangeListener).not.toHaveBeenCalled();
+          },
+        );
+      });
+
+      it('still publishes stateChange once a single amount changes', async () => {
+        await withController(
+          { state: repeatedState, isBasicFunctionality: () => false },
+          async ({ controller, messenger }) => {
+            await flushPromises();
+            const stateChangeListener = jest.fn();
+            messenger.subscribe(
+              'AssetsController:stateChange',
+              stateChangeListener,
+            );
+
+            await controller.handleAssetsUpdate(
+              {
+                ...repeatedResponse,
+                assetsBalance: {
+                  [MOCK_ACCOUNT_ID]: {
+                    [MOCK_ASSET_ID]: { amount: '2000000' },
+                    [MOCK_NATIVE_ASSET_ID]: { amount: '0' },
+                  },
+                },
+              },
+              'TestSource',
+            );
+
+            expect(stateChangeListener).toHaveBeenCalledTimes(1);
+            expect(
+              controller.state.assetsBalance[MOCK_ACCOUNT_ID]?.[MOCK_ASSET_ID],
+            ).toStrictEqual({ amount: '2000000' });
+          },
+        );
+      });
+    });
+
     it('reconciles a stale native type stored as erc20 when assetsInfo includes the asset', async () => {
       // Native (zero-address ERC-20) mis-stored as erc20 by an older version.
       const imxAssetId =

packages/assets-controller/src/AssetsController.ts

@@ -2708,12 +2708,6 @@ export class AssetsController extends BaseController<
           for (const [key, value] of Object.entries(
             normalizedResponse.assetsInfo,
           )) {
-            if (
-              !isEqual(previousState.assetsInfo[key as Caip19AssetId], value)
-            ) {
-              changedMetadata.push(key);
-            }
-
             const existing = metadata[key] as FungibleAssetMetadata | undefined;
             const incoming = value as FungibleAssetMetadata;
 
@@ -2722,17 +2716,28 @@ export class AssetsController extends BaseController<
             // the API). Preserve richer metadata already in state (e.g. from
             // pendingMetadata set by addCustomAsset) so that the correct
             // decimals/symbol/name/image are not overwritten with empty values.
-            if (existing && !incoming.symbol && !incoming.name) {
-              metadata[key] = {
-                ...existing,
-                ...incoming,
-                symbol: existing.symbol,
-                name: existing.name,
-                decimals: existing.decimals ?? incoming.decimals,
-                image: existing.image ?? incoming.image,
-              };
-            } else {
-              metadata[key] = value;
+            const nextMetadata =
+              existing && !incoming.symbol && !incoming.name
+                ? {
+                    ...existing,
+                    ...incoming,
+                    symbol: existing.symbol,
+                    name: existing.name,
+                    decimals: existing.decimals ?? incoming.decimals,
+                    image: existing.image ?? incoming.image,
+                  }
+                : value;
+
+            // Immer detects changes by reference, so assigning a deep-equal
+            // object still emits a patch and publishes a no-op stateChange.
+            if (
+              !isEqual(
+                previousState.assetsInfo[key as Caip19AssetId],
+                nextMetadata,
+              )
+            ) {
+              changedMetadata.push(key);
+              metadata[key] = nextMetadata;
             }
           }
         }
@@ -2829,15 +2834,22 @@ export class AssetsController extends BaseController<
                 });
               }
             }
-            balances[accountId] = effective;
+            // `mergeAccountBalances` always returns a new object. Comparing
+            // against the raw (possibly `undefined`) entry keeps a first-time
+            // account write while skipping an unchanged repeat.
+            if (!isEqual(previousState.assetsBalance[accountId], effective)) {
+              balances[accountId] = effective;
+            }
           }
         }
 
         if (normalizedResponse.assetsPrice) {
           for (const [key, value] of Object.entries(
             normalizedResponse.assetsPrice,
           )) {
-            prices[key] = value;
+            if (!isEqual(previousPrices[key as Caip19AssetId], value)) {
+              prices[key] = value;
+            }
           }
         }
       });