Cache access token

Avoid repetitively reading the access token from the keychain

Author: jacobsimeon

PocketKit/Sources/PocketKit/Authorization/AccessTokenStore.swift

@@ -25,7 +25,12 @@ class KeychainAccessTokenStore: AccessTokenStore {
         self.keychain = keychain
     }
 
+    private var _accessToken: String?
     var accessToken: String? {
+        guard _accessToken == nil else {
+            return _accessToken
+        }
+
         let query: [String: Any] = [
             kSecClass as String: kSecClassGenericPassword,
             kSecAttrService as String: Bundle.main.bundleIdentifier!,
@@ -44,10 +49,13 @@ class KeychainAccessTokenStore: AccessTokenStore {
             return nil
         }
 
+        _accessToken = token
         return token
     }
 
     func save(token: String) throws {
+        _accessToken = nil
+
         let query: [String: Any] = [
             kSecClass as String: kSecClassGenericPassword,
             kSecAttrService as String: Bundle.main.bundleIdentifier!,
@@ -65,6 +73,8 @@ class KeychainAccessTokenStore: AccessTokenStore {
     }
 
     func delete() throws {
+        _accessToken = nil
+
         let query: [String: Any] = [
             kSecClass as String: kSecClassGenericPassword,
             kSecAttrService as String: Bundle.main.bundleIdentifier!,

PocketKit/Tests/PocketKitTests/AccessTokenStoreTests.swift

@@ -51,6 +51,32 @@ class KeychainAccessTokenStoreTests: XCTestCase {
         )
     }
 
+    func test_accessToken_cachesValueFromKeychain() throws {
+        let store = KeychainAccessTokenStore(keychain: mockKeychain)
+        mockKeychain.copyMatchingResult = "the-token".data(using: .utf8) as CFTypeRef
+        mockKeychain.deleteReturnVal = 0
+
+        _ = store.accessToken // fetch from keychain
+        _ = store.accessToken // use in-memory cache
+
+        XCTAssertEqual(mockKeychain.copyMatchingCalls.count, 1)
+
+        try store.save(token: "new-token")
+        mockKeychain.copyMatchingResult = "new-token".data(using: .utf8) as CFTypeRef
+        XCTAssertEqual(store.accessToken, "new-token")
+        XCTAssertEqual(store.accessToken, "new-token")
+        XCTAssertEqual(mockKeychain.copyMatchingCalls.count, 2)
+
+        try store.delete()
+        mockKeychain.copyMatchingResult = nil
+        XCTAssertEqual(store.accessToken, nil)
+        XCTAssertEqual(mockKeychain.copyMatchingCalls.count, 3)
+
+        mockKeychain.copyMatchingResult = "even-newer-token".data(using: .utf8) as CFTypeRef
+        XCTAssertEqual(store.accessToken, "even-newer-token")
+        XCTAssertEqual(mockKeychain.copyMatchingCalls.count, 4)
+    }
+
     func test_accessToken_whenCopyMatchingSucceeds_returnsDecodedToken() {
         mockKeychain.copyMatchingResult = "the-token".data(using: .utf8) as CFTypeRef
         let store = KeychainAccessTokenStore(keychain: mockKeychain)