[#132] Error Throwing in Feature-Flag Stores (#139)

* Extended the protocols for feature-flag stores to support error throwing in reading, writing, and removing values, and saving changes * Updated the built-in stores * Updated `FeatureFlagResolver` * Updated tests
yakovmanshin · May 10, 2024 · ab7fff1 · ab7fff1
1 parent 8624a18
commit ab7fff1
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Showing 19 changed files with 417 additions and 150 deletions.
diff --git a/Sources/YMFF/FeatureFlagResolver/FeatureFlagResolver+Error.swift b/Sources/YMFF/FeatureFlagResolver/FeatureFlagResolver+Error.swift
@@ -20,14 +20,14 @@ extension FeatureFlagResolver {
         /// No feature-flag store contains a value for the given key.
         case valueNotFoundInStores(key: String)
 
+        /// The feature-flag store has thrown an error.
+        case storeError(any Swift.Error)
+
         /// Currently, optional values are not supported by the `FeatureFlagResolver`.
         ///
         /// - Note: Support for optional values will be added in [#130](https://github.com/yakovmanshin/YMFF/issues/130).
         case optionalValuesNotAllowed
 
-        /// The types of the old and new values don’t match.
-        case typeMismatch
-
     }
 
 }
diff --git a/Sources/YMFF/FeatureFlagResolver/FeatureFlagResolver.swift b/Sources/YMFF/FeatureFlagResolver/FeatureFlagResolver.swift
@@ -42,7 +42,7 @@ final public class FeatureFlagResolver {
         let mutableStores = getMutableStores()
         Task { [mutableStores] in
             for store in mutableStores {
-                await store.saveChanges()
+                try? await store.saveChanges()
             }
         }
     }
@@ -68,7 +68,11 @@ extension FeatureFlagResolver: FeatureFlagResolverProtocol {
 
         try await validateOverrideValue(newValue, forKey: key)
 
-        await mutableStores[0].setValue(newValue, forKey: key)
+        do {
+            try await mutableStores[0].setValue(newValue, forKey: key)
+        } catch {
+            throw Error.storeError(error)
+        }
     }
 
     public func removeValueFromMutableStore(using key: FeatureFlagKey) async throws {
@@ -77,7 +81,11 @@ extension FeatureFlagResolver: FeatureFlagResolverProtocol {
             throw Error.noStoreAvailable
         }
 
-        await mutableStores[0].removeValue(forKey: key)
+        do {
+            try await mutableStores[0].removeValue(forKey: key)
+        } catch {
+            throw Error.storeError(error)
+        }
     }
 
 }
@@ -101,7 +109,11 @@ extension FeatureFlagResolver: SynchronousFeatureFlagResolverProtocol {
 
         try validateOverrideValueSync(newValue, forKey: key)
 
-        syncMutableStores[0].setValueSync(newValue, forKey: key)
+        do {
+            try syncMutableStores[0].setValueSync(newValue, forKey: key)
+        } catch {
+            throw Error.storeError(error)
+        }
     }
 
     public func removeValueFromMutableStoreSync(using key: FeatureFlagKey) throws {
@@ -110,7 +122,11 @@ extension FeatureFlagResolver: SynchronousFeatureFlagResolverProtocol {
             throw Error.noStoreAvailable
         }
 
-        syncMutableStores[0].removeValueSync(forKey: key)
+        do {
+            try syncMutableStores[0].removeValueSync(forKey: key)
+        } catch {
+            throw Error.storeError(error)
+        }
     }
 
 }
@@ -149,10 +165,12 @@ extension FeatureFlagResolver {
 
         for store in matchingStores {
             if await store.containsValue(forKey: key) {
-                guard let value: Value = await store.value(forKey: key)
-                else { throw Error.typeMismatch }
-
-                return value
+                do {
+                    let value: Value = try await store.value(forKey: key)
+                    return value
+                } catch {
+                    throw Error.storeError(error)
+                }
             }
         }
 
@@ -167,10 +185,12 @@ extension FeatureFlagResolver {
 
         for store in matchingStores {
             if store.containsValueSync(forKey: key) {
-                guard let value: Value = store.valueSync(forKey: key)
-                else { throw Error.typeMismatch }
-
-                return value
+                do {
+                    let value: Value = try store.valueSync(forKey: key)
+                    return value
+                } catch {
+                    throw Error.storeError(error)
+                }
             }
         }
 

diff --git a/Sources/YMFF/FeatureFlagResolver/Store/CommonFeatureFlagStoreError.swift b/Sources/YMFF/FeatureFlagResolver/Store/CommonFeatureFlagStoreError.swift
@@ -0,0 +1,12 @@
+//
+//  CommonFeatureFlagStoreError.swift
+//  YMFF
+//
+//  Created by Yakov Manshin on 5/7/24.
+//  Copyright © 2024 Yakov Manshin. See the LICENSE file for license info.
+//
+
+enum CommonFeatureFlagStoreError: Error {
+    case valueNotFound(key: String)
+    case typeMismatch
+}
diff --git a/Sources/YMFF/FeatureFlagResolver/Store/RuntimeOverridesStore.swift b/Sources/YMFF/FeatureFlagResolver/Store/RuntimeOverridesStore.swift
@@ -31,8 +31,10 @@ extension RuntimeOverridesStore: SynchronousMutableFeatureFlagStore {
         store[key] != nil
     }
 
-    public func valueSync<Value>(forKey key: String) -> Value? {
-        store[key] as? Value
+    public func valueSync<Value>(forKey key: String) throws -> Value {
+        guard let anyValue = store[key] else { throw CommonFeatureFlagStoreError.valueNotFound(key: key) }
+        guard let value = anyValue as? Value else { throw CommonFeatureFlagStoreError.typeMismatch }
+        return value
     }
 
     public func setValueSync<Value>(_ value: Value, forKey key: String) {

diff --git a/Sources/YMFF/FeatureFlagResolver/Store/TransparentFeatureFlagStore.swift b/Sources/YMFF/FeatureFlagResolver/Store/TransparentFeatureFlagStore.swift
@@ -23,8 +23,10 @@ extension TransparentFeatureFlagStore: SynchronousFeatureFlagStore, FeatureFlagS
         self[key] != nil
     }
 
-    public func valueSync<V>(forKey key: String) -> V? {
-        self[key] as? V
+    public func valueSync<V>(forKey key: String) throws -> V {
+        guard let anyValue = self[key] else { throw CommonFeatureFlagStoreError.valueNotFound(key: key) }
+        guard let value = anyValue as? V else { throw CommonFeatureFlagStoreError.typeMismatch }
+        return value
     }
 
 }
diff --git a/Sources/YMFF/FeatureFlagResolver/Store/UserDefaultsStore.swift b/Sources/YMFF/FeatureFlagResolver/Store/UserDefaultsStore.swift
@@ -38,8 +38,12 @@ extension UserDefaultsStore: SynchronousMutableFeatureFlagStore {
         userDefaults.object(forKey: key) != nil
     }
 
-    public func valueSync<Value>(forKey key: String) -> Value? {
-        userDefaults.object(forKey: key) as? Value
+    public func valueSync<Value>(forKey key: String) throws -> Value {
+        guard let anyValue = userDefaults.object(forKey: key) else {
+            throw CommonFeatureFlagStoreError.valueNotFound(key: key)
+        }
+        guard let value = anyValue as? Value else { throw CommonFeatureFlagStoreError.typeMismatch }
+        return value
     }
 
     public func setValueSync<Value>(_ value: Value, forKey key: String) {

diff --git a/Sources/YMFFProtocols/FeatureFlagResolver/Store/FeatureFlagStore.swift b/Sources/YMFFProtocols/FeatureFlagResolver/Store/FeatureFlagStore.swift
@@ -17,6 +17,6 @@ public protocol FeatureFlagStore {
     /// Retrieves a feature flag value by its key.
     ///
     /// - Parameter key: *Required.* The key that points to a feature flag value in the store.
-    func value<Value>(forKey key: String) async -> Value?
+    func value<Value>(forKey key: String) async throws -> Value
 
 }
diff --git a/Sources/YMFFProtocols/FeatureFlagResolver/Store/MutableFeatureFlagStore.swift b/Sources/YMFFProtocols/FeatureFlagResolver/Store/MutableFeatureFlagStore.swift
@@ -14,17 +14,17 @@ public protocol MutableFeatureFlagStore: AnyObject, FeatureFlagStore {
     /// - Parameters:
     ///   - value: *Required.* The value to record.
     ///   - key: *Required.* The key used to address the value.
-    func setValue<Value>(_ value: Value, forKey key: String) async
+    func setValue<Value>(_ value: Value, forKey key: String) async throws
 
     /// Removes the value from the store.
     ///
     /// - Parameter key: *Required.* The key used to address the value.
-    func removeValue(forKey key: String) async
+    func removeValue(forKey key: String) async throws
 
     /// Immediately saves changed values so they’re not lost.
     ///
     /// + This method can be called when work with the feature flag store is finished.
-    func saveChanges() async
+    func saveChanges() async throws
 
 }
 
@@ -33,6 +33,6 @@ public protocol MutableFeatureFlagStore: AnyObject, FeatureFlagStore {
 extension MutableFeatureFlagStore {
 
     // Not all kinds of feature flag stores need this method, so it’s optional to implement.
-    public func saveChanges() async { }
+    public func saveChanges() async throws { }
 
 }
diff --git a/Sources/YMFFProtocols/FeatureFlagResolver/Store/SynchronousFeatureFlagStore.swift b/Sources/YMFFProtocols/FeatureFlagResolver/Store/SynchronousFeatureFlagStore.swift
@@ -16,7 +16,7 @@ public protocol SynchronousFeatureFlagStore: FeatureFlagStore {
     /// Retrieves a feature flag value by its key.
     ///
     /// - Parameter key: *Required.* The key that points to a feature flag value in the store.
-    func valueSync<Value>(forKey key: String) -> Value?
+    func valueSync<Value>(forKey key: String) throws -> Value
 
 }
 
@@ -28,8 +28,8 @@ extension SynchronousFeatureFlagStore {
         containsValueSync(forKey: key)
     }
 
-    public func value<Value>(forKey key: String) async -> Value? {
-        valueSync(forKey: key)
+    public func value<Value>(forKey key: String) async throws -> Value {
+        try valueSync(forKey: key)
     }
 
 }
diff --git a/Sources/YMFFProtocols/FeatureFlagResolver/Store/SynchronousMutableFeatureFlagStore.swift b/Sources/YMFFProtocols/FeatureFlagResolver/Store/SynchronousMutableFeatureFlagStore.swift
@@ -13,34 +13,34 @@ public protocol SynchronousMutableFeatureFlagStore: SynchronousFeatureFlagStore,
     /// - Parameters:
     ///   - value: *Required.* The value to record.
     ///   - key: *Required.* The key used to address the value.
-    func setValueSync<Value>(_ value: Value, forKey key: String)
+    func setValueSync<Value>(_ value: Value, forKey key: String) throws
 
     /// Removes the value from the store.
     ///
     /// - Parameter key: *Required.* The key used to address the value.
-    func removeValueSync(forKey key: String)
+    func removeValueSync(forKey key: String) throws
 
     /// Immediately saves changed values so they’re not lost.
     ///
     /// + This method can be called when work with the feature flag store is finished.
-    func saveChangesSync()
+    func saveChangesSync() throws
 
 }
 
 // MARK: - Async Requirements
 
 extension SynchronousMutableFeatureFlagStore {
 
-    public func setValue<Value>(_ value: Value, forKey key: String) async {
-        setValueSync(value, forKey: key)
+    public func setValue<Value>(_ value: Value, forKey key: String) async throws {
+        try setValueSync(value, forKey: key)
     }
 
-    public func removeValue(forKey key: String) async {
-        removeValueSync(forKey: key)
+    public func removeValue(forKey key: String) async throws {
+        try removeValueSync(forKey: key)
     }
 
-    public func saveChanges() async {
-        saveChangesSync()
+    public func saveChanges() async throws {
+        try saveChangesSync()
     }
 
 }
@@ -49,6 +49,6 @@ extension SynchronousMutableFeatureFlagStore {
 
 extension SynchronousMutableFeatureFlagStore {
 
-    public func saveChangesSync() { }
+    public func saveChangesSync() throws { }
 
 }