Update useBreakpoints to use a single set of event listeners

.changeset/nice-lizards-dream.md

@@ -0,0 +1,5 @@
+---
+"@shopify/polaris": minor
+---
+
+Updated `useBreakpoints` to use a single set of event listeners

polaris-react/src/utilities/breakpoints.ts

@@ -30,13 +30,13 @@ const noWindowMatches: MediaQueryList = {
 function noop() {}
 
 export function navigationBarCollapsed() {
-  return typeof window === 'undefined'
+  return isServer
     ? noWindowMatches
     : window.matchMedia(`(max-width: ${Breakpoints.navigationBarCollapsed})`);
 }
 
 export function stackedContent() {
-  return typeof window === 'undefined'
+  return isServer
     ? noWindowMatches
     : window.matchMedia(`(max-width: ${Breakpoints.stackedContent})`);
 }
@@ -56,40 +56,45 @@ type BreakpointsMatches = {
   [DirectionAlias in BreakpointsDirectionAlias]: boolean;
 };
 
+const hookCallbacks = new Set<
+  (breakpointAlias: BreakpointsDirectionAlias, matches: boolean) => void
+>();
 const breakpointsQueryEntries = getBreakpointsQueryEntries(
   themeDefault.breakpoints,
 );
 
-function getMatches(
-  defaults?: UseBreakpointsOptions['defaults'],
-  /**
-   * Used to force defaults on initial client side render so they match SSR
-   * values and hence avoid a Hydration error.
-   */
-  forceDefaults?: boolean,
-) {
-  if (!isServer && !forceDefaults) {
-    return Object.fromEntries(
-      breakpointsQueryEntries.map(([directionAlias, query]) => [
-        directionAlias,
-        window.matchMedia(query).matches,
-      ]),
-    ) as BreakpointsMatches;
-  }
-
-  if (typeof defaults === 'object' && defaults !== null) {
-    return Object.fromEntries(
-      breakpointsQueryEntries.map(([directionAlias]) => [
-        directionAlias,
-        defaults[directionAlias] ?? false,
-      ]),
-    ) as BreakpointsMatches;
-  }
+if (!isServer) {
+  breakpointsQueryEntries.forEach(([breakpointAlias, query]) => {
+    const eventListener = (event: {matches: boolean}) => {
+      for (const hookCallback of hookCallbacks) {
+        hookCallback(breakpointAlias, event.matches);
+      }
+    };
+    const mql = window.matchMedia(query);
+    if (mql.addListener) {
+      mql.addListener(eventListener);
+    } else {
+      mql.addEventListener('change', eventListener);
+    }
+  });
+}
 
+function getDefaultMatches(defaults?: UseBreakpointsOptions['defaults']) {
   return Object.fromEntries(
     breakpointsQueryEntries.map(([directionAlias]) => [
       directionAlias,
-      defaults ?? false,
+      typeof defaults === 'boolean'
+        ? defaults
+        : defaults?.[directionAlias] ?? false,
+    ]),
+  ) as BreakpointsMatches;
+}
+
+function getLiveMatches() {
+  return Object.fromEntries(
+    breakpointsQueryEntries.map(([directionAlias, query]) => [
+      directionAlias,
+      window.matchMedia(query).matches,
     ]),
   ) as BreakpointsMatches;
 }
@@ -129,36 +134,28 @@ export function useBreakpoints(options?: UseBreakpointsOptions) {
   // Later, in the effect, we will call this again on the client side without
   // any defaults to trigger a more accurate client side evaluation.
   const [breakpoints, setBreakpoints] = useState(
-    getMatches(options?.defaults, true),
+    getDefaultMatches(options?.defaults),
   );
 
   useIsomorphicLayoutEffect(() => {
-    const mediaQueryLists = breakpointsQueryEntries.map(([_, query]) =>
-      window.matchMedia(query),
-    );
-
-    const handler = () => setBreakpoints(getMatches());
-
-    mediaQueryLists.forEach((mql) => {
-      if (mql.addListener) {
-        mql.addListener(handler);
-      } else {
-        mql.addEventListener('change', handler);
-      }
-    });
-
-    // Trigger the breakpoint recalculation at least once client-side to ensure
-    // we don't have stale default values from SSR.
-    handler();
+    // Now that we're client side, get the real values
+    setBreakpoints(getLiveMatches());
+
+    // Register a callback to set the breakpoints object whenever there's a
+    // change in the future
+    const callback = (
+      breakpointAlias: BreakpointsDirectionAlias,
+      matches: boolean,
+    ) => {
+      setBreakpoints((prevBreakpoints) => ({
+        ...prevBreakpoints,
+        [breakpointAlias]: matches,
+      }));
+    };
+    hookCallbacks.add(callback);
 
     return () => {
-      mediaQueryLists.forEach((mql) => {
-        if (mql.removeListener) {
-          mql.removeListener(handler);
-        } else {
-          mql.removeEventListener('change', handler);
-        }
-      });
+      hookCallbacks.delete(callback);
     };
   }, []);
 

polaris-react/tests/setup/tests.ts

@@ -3,16 +3,22 @@ import {matchMedia} from '@shopify/jest-dom-mocks';
 import '@shopify/react-testing/matchers';
 import './matchers';
 
+// Mock once before test files are imported so uses of `window.matchMedia`
+// outside of components still works.
+if (typeof window !== 'undefined' && !matchMedia.isMocked()) {
+  matchMedia.mock();
+}
+
 // eslint-disable-next-line jest/require-top-level-describe
 beforeEach(() => {
-  if (typeof window !== 'undefined') {
+  if (typeof window !== 'undefined' && !matchMedia.isMocked()) {
     matchMedia.mock();
   }
 });
 
 // eslint-disable-next-line jest/require-top-level-describe
 afterEach(() => {
-  if (typeof window !== 'undefined') {
+  if (typeof window !== 'undefined' && matchMedia.isMocked()) {
     matchMedia.restore();
   }
   destroyAll();