Stop looking in localStorage for temporary cache (#8579)

This pull request simplifies the behavior of the `getTemporaryCache`
method in `BrowserCacheManager` by removing legacy fallback logic and
updates the related unit tests accordingly. The main focus is to ensure
that temporary cache retrieval is streamlined and no longer checks local
storage for items set by old versions.

Fixes #8577

**Browser cache logic simplification:**
-
[`BrowserCacheManager.ts`](diffhunk://#diff-9fe0cda3d1225c92740f98cfd73639c5db18bf24234c273756a855e5b48adae2R1904-R1906):
Removed fallback logic in `getTemporaryCache` that previously checked
`localStorage` for temporary cache items if not found in session/memory
storage. The method now only checks the intended temporary cache
storage. Added a trace log for method invocation.

**Test updates:**
-
[`BrowserCacheManager.spec.ts`](diffhunk://#diff-1f474f3b5ffedcb4da969f60d720532be75a02c6d91e65b7d1e3c107b0a4f13dL1878-L1900):
Removed the test that verified fallback to `localStorage` in
`getTemporaryCache`, as this behavior is no longer supported.

---------

Co-authored-by: -g <-g>

Author: tnorling

change/@azure-msal-browser-4e066b2f-6995-49dc-8d30-fb502ab69cf9.json

@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "Stop looking in localStorage for temporary cache [#8579](https://github.com/AzureAD/microsoft-authentication-library-for-js/pull/8579)",
+  "packageName": "@azure/msal-browser",
+  "email": "-g",
+  "dependentChangeType": "patch"
+}

lib/msal-browser/src/cache/BrowserCacheManager.ts

@@ -1901,30 +1901,12 @@ export class BrowserCacheManager extends CacheManager {
         correlationId: string,
         generateKey?: boolean
     ): string | null {
+        this.logger.trace(
+            "BrowserCacheManager.getTemporaryCache called",
+            correlationId
+        );
         const key = generateKey ? this.generateCacheKey(cacheKey) : cacheKey;
-        const value = this.temporaryCacheStorage.getItem(key);
-        if (!value) {
-            // If temp cache item not found in session/memory, check local storage for items set by old versions
-            if (
-                this.cacheConfig.cacheLocation ===
-                BrowserCacheLocation.LocalStorage
-            ) {
-                const item = this.browserStorage.getItem(key);
-                if (item) {
-                    this.logger.trace(
-                        "BrowserCacheManager.getTemporaryCache: Temporary cache item found in local storage",
-                        correlationId
-                    );
-                    return item;
-                }
-            }
-            this.logger.trace(
-                "BrowserCacheManager.getTemporaryCache: No cache item found in local storage",
-                correlationId
-            );
-            return null;
-        }
-        return value;
+        return this.temporaryCacheStorage.getItem(key);
     }
 
     /**

lib/msal-browser/test/cache/BrowserCacheManager.spec.ts

@@ -1875,29 +1875,6 @@ describe("BrowserCacheManager tests", () => {
             expect(window.sessionStorage.getItem(msalCacheKey2)).toBe(cacheVal);
         });
 
-        it("getTemporaryCache falls back to local storage if not found in session/memory storage", () => {
-            const testTempItemKey = "test-temp-item-key";
-            const testTempItemValue = "test-temp-item-value";
-            window.localStorage.setItem(testTempItemKey, testTempItemValue);
-            browserLocalStorage = new BrowserCacheManager(
-                TEST_CONFIG.MSAL_CLIENT_ID,
-                {
-                    ...cacheConfig,
-                    cacheLocation: BrowserCacheLocation.LocalStorage,
-                },
-                browserCrypto,
-                logger,
-                new StubPerformanceClient(),
-                new EventHandler()
-            );
-            expect(
-                browserLocalStorage.getTemporaryCache(
-                    testTempItemKey,
-                    TEST_CONFIG.CORRELATION_ID
-                )
-            ).toBe(testTempItemValue);
-        });
-
         it("setItem", () => {
             window.sessionStorage.setItem(msalCacheKey, cacheVal);
             window.localStorage.setItem(msalCacheKey2, cacheVal);