Add option to allow ContextKey overwrite on unsafeAdd (#5)

* Add option to allow ContextKey overwrite on `unsafeAdd`

* Swiftlint

Author: bauer-andreas

Sources/ApodiniContext/CodableContextKey.swift

@@ -24,10 +24,12 @@ private let encoder = JSONEncoder()
 private let decoder = JSONDecoder()
 
 extension CodableContextKey {
+    /// Default identifier is derived from the swift type name
     public static var identifier: String {
         "\(Self.self)"
     }
 
+    /// Default implementation for anyEncode to base64 string.
     public static func anyEncode(value: Any) throws -> String {
         guard let value = value as? Self.Value else {
             fatalError("CodableContextKey.anyEncode(value:) received illegal value type \(type(of: value)) instead of \(Value.self)")
@@ -38,6 +40,7 @@ extension CodableContextKey {
             .base64EncodedString()
     }
 
+    /// Default implementation for decode from base64 string.
     public static func decode(from base64String: String) throws -> Value {
         guard let data = Data(base64Encoded: base64String) else {
             fatalError("Failed to unwrap bas64 encoded data string: \(base64String)")

Sources/ApodiniContext/Context.swift

@@ -89,10 +89,12 @@ public struct Context: ContextKeyRetrievable {
     /// - Parameters:
     ///   - contextKey: The context to add value for.
     ///   - value: The value to add.
-    public func unsafeAdd<C: OptionalContextKey>(_ contextKey: C.Type = C.self, value: C.Value) {
+    ///   - allowOverwrite: This Bool controls if the unsafe addition should allow overwriting an existing entry.
+    ///     Use this option with caution! This method does NOT reduce multiple values for the same key. It OVERWRITES!
+    public func unsafeAdd<C: OptionalContextKey>(_ contextKey: C.Type = C.self, value: C.Value, allowOverwrite: Bool = false) {
         let key = ObjectIdentifier(contextKey)
 
-        precondition(entries[key] == nil, "Cannot overwrite existing ContextKey entry with `unsafeAdd`: \(C.self): \(value)")
+        precondition(entries[key] == nil || allowOverwrite, "Cannot overwrite existing ContextKey entry with `unsafeAdd`: \(C.self): \(value)")
         if let codableContextKey = contextKey as? AnyCodableContextKey.Type {
             // we need to prevent this. as Otherwise we would need to handle merging this stuff which get really complex
             precondition(decodedEntries[codableContextKey.identifier] == nil, "Cannot overwrite existing CodableContextKey entry with `unsafeAdd`: \(C.self): \(value)")

Tests/ApodiniContextTests/ContextKeyTests.swift

@@ -107,11 +107,27 @@ class ContextKeyTests: XCTestCase {
         let decoder = FineJSONDecoder()
 
         let encodedContext = try encoder.encode(context)
-        XCTAssertEqual(String(data: encodedContext, encoding: .utf8), "{\"CodableArrayStringContextKey\":\"WyJIZWxsbyBTdW4iXQ==\",\"CodableStringContextKey\":\"IkhlbGxvIFdvcmxkIg==\"}")
+        XCTAssertEqual(
+            String(data: encodedContext, encoding: .utf8),
+            "{\"CodableArrayStringContextKey\":\"WyJIZWxsbyBTdW4iXQ==\",\"CodableStringContextKey\":\"IkhlbGxvIFdvcmxkIg==\"}"
+        )
         let decodedContext = try decoder.decode(Context.self, from: encodedContext)
 
         XCTAssertEqual(decodedContext.get(valueFor: CodableStringContextKey.self), "Hello World")
         XCTAssertEqual(decodedContext.get(valueFor: RequiredCodableStringContextKey.self), "Default Value!")
         XCTAssertEqual(decodedContext.get(valueFor: CodableArrayStringContextKey.self), ["Hello Sun"])
     }
+
+    func testUnsafeAddAllowingOverwrite() {
+        struct CodableStringContextKey: CodableContextKey {
+            typealias Value = String
+        }
+
+        let context = Context()
+
+        context.unsafeAdd(CodableStringContextKey.self, value: "Hello World")
+        XCTAssertEqual(context.get(valueFor: CodableStringContextKey.self), "Hello World")
+        context.unsafeAdd(CodableStringContextKey.self, value: "Hello Mars", allowOverwrite: true)
+        XCTAssertEqual(context.get(valueFor: CodableStringContextKey.self), "Hello Mars")
+    }
 }