fix: remove cookies with max-age=0 from cookie store (#2275)

src/core/utils/cookieStore.ts

@@ -75,6 +75,11 @@ class WebStorageCookieStore extends Store {
     callback: (error: Error | null) => void,
   ): void {
     try {
+      // Never set cookies with `maxAge` of `0`.
+      if (cookie.maxAge === 0) {
+        return
+      }
+
       const store = this.getStore()
       store.push(cookie)
       this.updateStore(store)
@@ -90,6 +95,21 @@ class WebStorageCookieStore extends Store {
     newCookie: CookieInstance,
     callback: (error: Error | null) => void,
   ): void {
+    /**
+     * If updating a cookie with `maxAge` of `0`, remove it from the store.
+     * Otherwise, two cookie entries will be created.
+     * @see https://github.com/mswjs/msw/issues/2272
+     */
+    if (newCookie.maxAge === 0) {
+      this.removeCookie(
+        newCookie.domain || '',
+        newCookie.path || '',
+        newCookie.key,
+        callback,
+      )
+      return
+    }
+
     this.putCookie(newCookie, callback)
   }
 

test/browser/rest-api/request/request-cookies.test.ts

@@ -177,7 +177,6 @@ test('inherits mocked "HttpOnly" cookies', async ({
 test('respects cookie "Path" when exposing cookies', async ({
   loadExample,
   fetch,
-  page,
 }) => {
   await loadExample(require.resolve('./request-cookies.mocks.ts'))
 
@@ -203,3 +202,30 @@ test('respects cookie "Path" when exposing cookies', async ({
     mockedCookie: 'mockedValue',
   })
 })
+
+test('deletes a cookie when sending "max-age=0" in a mocked response', async ({
+  loadExample,
+  fetch,
+}) => {
+  await loadExample(require.resolve('./request-cookies.mocks.ts'))
+
+  // First, set the cookie.
+  await fetch('/set-cookies', {
+    method: 'POST',
+    body: `mockedCookie=mockedValue`,
+  })
+
+  // Must forward the mocked cookied to the matching request.
+  await expect(fetch('/cookies').then((res) => res.json())).resolves.toEqual({
+    mockedCookie: 'mockedValue',
+  })
+
+  // Next, delete the cookie by setting "max-age=0".
+  await fetch('/set-cookies', {
+    method: 'POST',
+    body: `mockedCookie=mockedValue; max-age=0`,
+  })
+
+  // Must NOT have any cookies on the matching request.
+  await expect(fetch('/cookies').then((res) => res.json())).resolves.toEqual({})
+})