[api-upload-refactor] Add test target, relax decode constraints, add HTTPBody + MultipartForm

- Package: new LCEssentialsTests target (runs on iOS simulator)
- JSONDecoder.decode: T: Codable -> T: Decodable & Sendable (4 overloads);
  remove try! in decode(fromURL:); honour encoding param in decode(_:using:)
- Propagate & Sendable to Data.object, Dictionary.toObjetct, API.request return
- LCEHTTPBody: HTTPBody protocol, JSONBody, FormURLEncodedBody, RawBody, factories
- LCEMultipartForm: multipart builder, OutputStream-streamed serialize(),
  in-memory + on-disk file parts, ported mimeType(for:)
- Tests: StubURLProtocol harness + 15 tests

Tests/LCEssentialsTests/HTTPBodyTests.swift

@@ -0,0 +1,58 @@
+import XCTest
+@testable import LCEssentials
+
+private struct SamplePayload: Encodable, Sendable {
+    let name: String
+    let age: Int
+}
+
+final class HTTPBodyTests: XCTestCase {
+
+    // MARK: - JSONBody
+
+    func testJSONBodyEncodesPayloadAndContentType() throws {
+        let payload = SamplePayload(name: "loverde", age: 3)
+        let (data, contentType) = try JSONBody(payload).encoded()
+
+        XCTAssertEqual(contentType, "application/json; charset=UTF-8")
+
+        let decoded = try JSONDecoder().decode([String: AnyDecodable].self, from: data)
+        XCTAssertEqual(decoded["name"]?.value as? String, "loverde")
+        XCTAssertEqual(decoded["age"]?.value as? Int, 3)
+    }
+
+    func testJSONBodyFactory() throws {
+        let (data, _) = try jsonBody(SamplePayload(name: "x", age: 1)).encoded()
+        XCTAssertFalse(data.isEmpty)
+    }
+
+    // MARK: - FormURLEncodedBody
+
+    func testFormURLEncodedEncodesPairsAndPercentEscapes() throws {
+        let (data, contentType) = try FormURLEncodedBody(["a": "1", "b": "two words"]).encoded()
+
+        XCTAssertEqual(contentType, "application/x-www-form-urlencoded; charset=UTF-8")
+
+        let pairs = Set(String(data: data, encoding: .utf8)!.split(separator: "&").map(String.init))
+        XCTAssertEqual(pairs, ["a=1", "b=two%20words"])
+    }
+
+    func testFormURLEncodedEscapesReservedCharactersInsteadOfDropping() throws {
+        let (data, _) = try FormURLEncodedBody(["q": "a&b=c"]).encoded()
+        let body = String(data: data, encoding: .utf8)!
+        XCTAssertEqual(body, "q=a%26b%3Dc")
+    }
+}
+
+/// Minimal type-erased decoder for asserting JSON shape in tests.
+struct AnyDecodable: Decodable {
+    let value: Any
+    init(from decoder: Decoder) throws {
+        let c = try decoder.singleValueContainer()
+        if let i = try? c.decode(Int.self) { value = i }
+        else if let s = try? c.decode(String.self) { value = s }
+        else if let b = try? c.decode(Bool.self) { value = b }
+        else if let d = try? c.decode(Double.self) { value = d }
+        else { value = "" }
+    }
+}

Tests/LCEssentialsTests/JSONDecoderDecodeTests.swift

@@ -0,0 +1,26 @@
+import XCTest
+@testable import LCEssentials
+
+private struct OnlyDecodable: Decodable, Sendable, Equatable {
+    let id: Int
+    let name: String
+}
+
+final class JSONDecoderDecodeTests: XCTestCase {
+
+    func testDecodesTypeThatIsDecodableAndSendableButNotEncodable() throws {
+        let data = Data(#"{"id":7,"name":"loverde"}"#.utf8)
+        let value: OnlyDecodable = try JSONDecoder.decode(data: data)
+        XCTAssertEqual(value, OnlyDecodable(id: 7, name: "loverde"))
+    }
+
+    func testDecodeFromStringOverload() throws {
+        let value: OnlyDecodable = try JSONDecoder.decode(#"{"id":1,"name":"a"}"#)
+        XCTAssertEqual(value, OnlyDecodable(id: 1, name: "a"))
+    }
+
+    func testDecodeFromURLThrowsInsteadOfCrashingOnMissingFile() {
+        let missing = URL(fileURLWithPath: "/tmp/does-not-exist-\(UUID().uuidString).json")
+        XCTAssertThrowsError(try JSONDecoder.decode(fromURL: missing) as OnlyDecodable)
+    }
+}

Tests/LCEssentialsTests/MultipartFormTests.swift

@@ -0,0 +1,106 @@
+import XCTest
+@testable import LCEssentials
+
+final class MultipartFormTests: XCTestCase {
+
+    private func readSerialized(_ form: MultipartForm) throws -> (body: Data, contentType: String, url: URL) {
+        let result = try form.serialize()
+        let data = try Data(contentsOf: result.fileURL)
+        return (data, result.contentType, result.fileURL)
+    }
+
+    private func addCleanup(_ url: URL) {
+        addTeardownBlock { try? FileManager.default.removeItem(at: url) }
+    }
+
+    // MARK: - Fields
+
+    func testFieldPartHasNoContentTypeLine() throws {
+        var form = MultipartForm()
+        form.field("caption", "hello world")
+
+        let (body, contentType, url) = try readSerialized(form)
+        addCleanup(url)
+        let text = String(data: body, encoding: .utf8)!
+
+        XCTAssertTrue(contentType.hasPrefix("multipart/form-data; boundary="))
+        let boundary = String(contentType.split(separator: "=", maxSplits: 1)[1])
+
+        XCTAssertEqual(text, [
+            "--\(boundary)\r\n",
+            "Content-Disposition: form-data; name=\"caption\"\r\n",
+            "\r\n",
+            "hello world\r\n",
+            "--\(boundary)--\r\n"
+        ].joined())
+    }
+
+    // MARK: - In-memory data file
+
+    func testDataFilePartCarriesFilenameAndMimeAndRawBytes() throws {
+        let png = Data([0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A, 0x00, 0xFF])
+        var form = MultipartForm()
+        form.file("photo", data: png, filename: "p.png")
+
+        let (body, contentType, url) = try readSerialized(form)
+        addCleanup(url)
+        let boundary = String(contentType.split(separator: "=", maxSplits: 1)[1])
+        let text = String(data: body, encoding: .isoLatin1)!
+
+        XCTAssertTrue(text.contains("Content-Disposition: form-data; name=\"photo\"; filename=\"p.png\"\r\n"))
+        XCTAssertTrue(text.contains("Content-Type: image/png\r\n"))
+        XCTAssertTrue(text.hasSuffix("--\(boundary)--\r\n"))
+
+        // raw bytes appear verbatim between the blank line and the trailing CRLF
+        let marker = Data("\r\n\r\n".utf8)
+        let range = body.range(of: marker)!
+        let afterHeader = body[range.upperBound...]
+        XCTAssertTrue(afterHeader.starts(with: png))
+    }
+
+    func testExplicitMimeOverridesGuess() throws {
+        var form = MultipartForm()
+        form.file("f", data: Data("x".utf8), filename: "a.png", mime: "application/octet-stream")
+        let (body, _, url) = try readSerialized(form)
+        addCleanup(url)
+        XCTAssertTrue(String(data: body, encoding: .utf8)!.contains("Content-Type: application/octet-stream\r\n"))
+    }
+
+    // MARK: - Disk file, streamed
+
+    func testDiskFilePartIsStreamedAndContentMatches() throws {
+        let big = Data((0..<(2 * 1024 * 1024)).map { UInt8($0 % 251) })
+        let src = FileManager.default.temporaryDirectory.appendingPathComponent("src-\(UUID().uuidString).bin")
+        try big.write(to: src)
+        addCleanup(src)
+
+        var form = MultipartForm()
+        form.field("kind", "raw")
+        form.file("doc", url: src)
+
+        let (body, contentType, out) = try readSerialized(form)
+        addCleanup(out)
+        let boundary = String(contentType.split(separator: "=", maxSplits: 1)[1])
+
+        // header uses the source filename
+        XCTAssertTrue(String(data: body.prefix(400), encoding: .isoLatin1)!
+            .contains("filename=\"\(src.lastPathComponent)\""))
+
+        // the 2 MB payload is present verbatim
+        let marker = Data("Content-Type: application/octet-stream\r\n\r\n".utf8)
+        let r = body.range(of: marker)!
+        let payload = body[r.upperBound..<(body.index(r.upperBound, offsetBy: big.count))]
+        XCTAssertEqual(Data(payload), big)
+
+        XCTAssertTrue(String(data: body.suffix(boundary.count + 8), encoding: .utf8)!
+            .hasSuffix("--\(boundary)--\r\n"))
+    }
+
+    // MARK: - MIME lookup
+
+    func testMimeTypeLookup() {
+        XCTAssertEqual(MultipartForm.mimeType(for: "a.jpg"), "image/jpeg")
+        XCTAssertEqual(MultipartForm.mimeType(for: "a.PDF"), "application/pdf")
+        XCTAssertEqual(MultipartForm.mimeType(for: "a.unknownext"), "application/octet-stream")
+    }
+}

Tests/LCEssentialsTests/SmokeTests.swift

@@ -0,0 +1,8 @@
+import XCTest
+@testable import LCEssentials
+
+final class SmokeTests: XCTestCase {
+    func testTargetBuildsAndRuns() {
+        XCTAssertTrue(true)
+    }
+}

Tests/LCEssentialsTests/Support/StubURLProtocol.swift

@@ -0,0 +1,116 @@
+import Foundation
+
+/// Test double for `URLProtocol`. Intercepts every request on a `URLSession`
+/// configured with it, records the outgoing `URLRequest`, and replays a canned
+/// response or error supplied by the test.
+///
+/// Register via:
+/// ```
+/// let cfg = URLSessionConfiguration.ephemeral
+/// cfg.protocolClasses = [StubURLProtocol.self]
+/// let session = URLSession(configuration: cfg)
+/// ```
+final class StubURLProtocol: URLProtocol, @unchecked Sendable {
+
+    struct Stub {
+        var statusCode: Int = 200
+        var headers: [String: String] = ["Content-Type": "application/json"]
+        var body: Data = Data()
+        var error: Error?
+        /// Bytes reported through `URLSession`'s upload progress, in order.
+        var uploadProgressChunks: [Int] = []
+    }
+
+    // MARK: - Test-facing state (guarded)
+
+    private static let lock = NSLock()
+    // Access is serialised through `lock`; the unsafe opt-out is the documented
+    // pattern for lock-guarded mutable statics under strict concurrency.
+    nonisolated(unsafe) private static var _stub = Stub()
+    nonisolated(unsafe) private static var _capturedRequests: [URLRequest] = []
+    nonisolated(unsafe) private static var _capturedBodies: [Data] = []
+
+    static func setStub(_ stub: Stub) {
+        lock.lock(); defer { lock.unlock() }
+        _stub = stub
+        _capturedRequests = []
+        _capturedBodies = []
+    }
+
+    static func reset() { setStub(Stub()) }
+
+    static var capturedRequests: [URLRequest] {
+        lock.lock(); defer { lock.unlock() }
+        return _capturedRequests
+    }
+
+    /// Body of the last intercepted request. `URLProtocol` strips `httpBody` for
+    /// stream bodies, so this reads `httpBodyStream` when needed.
+    static var lastCapturedBody: Data? {
+        lock.lock(); defer { lock.unlock() }
+        return _capturedBodies.last
+    }
+
+    static var requestCount: Int {
+        lock.lock(); defer { lock.unlock() }
+        return _capturedRequests.count
+    }
+
+    private static func currentStub() -> Stub {
+        lock.lock(); defer { lock.unlock() }
+        return _stub
+    }
+
+    private static func record(_ request: URLRequest, body: Data) {
+        lock.lock(); defer { lock.unlock() }
+        _capturedRequests.append(request)
+        _capturedBodies.append(body)
+    }
+
+    // MARK: - URLProtocol
+
+    override class func canInit(with request: URLRequest) -> Bool { true }
+
+    override class func canonicalRequest(for request: URLRequest) -> URLRequest { request }
+
+    override func startLoading() {
+        let stub = Self.currentStub()
+        Self.record(request, body: Self.bodyData(from: request))
+
+        guard let client = client else { return }
+
+        if let error = stub.error {
+            client.urlProtocol(self, didFailWithError: error)
+            return
+        }
+
+        let url = request.url ?? URL(string: "https://stub.invalid")!
+        let response = HTTPURLResponse(url: url,
+                                       statusCode: stub.statusCode,
+                                       httpVersion: "HTTP/1.1",
+                                       headerFields: stub.headers)!
+        client.urlProtocol(self, didReceive: response, cacheStoragePolicy: .notAllowed)
+        client.urlProtocol(self, didLoad: stub.body)
+        client.urlProtocolDidFinishLoading(self)
+    }
+
+    override func stopLoading() {}
+
+    // MARK: - Body extraction
+
+    private static func bodyData(from request: URLRequest) -> Data {
+        if let body = request.httpBody { return body }
+        guard let stream = request.httpBodyStream else { return Data() }
+        stream.open()
+        defer { stream.close() }
+        var data = Data()
+        let bufferSize = 64 * 1024
+        var buffer = [UInt8](repeating: 0, count: bufferSize)
+        while stream.hasBytesAvailable {
+            let read = stream.read(&buffer, maxLength: bufferSize)
+            if read <= 0 { break }
+            data.append(buffer, count: read)
+        }
+        return data
+    }
+}

Tests/LCEssentialsTests/Support/StubURLProtocolTests.swift

@@ -0,0 +1,47 @@
+import XCTest
+
+final class StubURLProtocolTests: XCTestCase {
+
+    private func makeSession() -> URLSession {
+        let cfg = URLSessionConfiguration.ephemeral
+        cfg.protocolClasses = [StubURLProtocol.self]
+        return URLSession(configuration: cfg)
+    }
+
+    override func tearDown() {
+        StubURLProtocol.reset()
+        super.tearDown()
+    }
+
+    func testReplaysCannedResponseAndCapturesRequest() async throws {
+        var stub = StubURLProtocol.Stub()
+        stub.statusCode = 201
+        stub.body = Data(#"{"ok":true}"#.utf8)
+        StubURLProtocol.setStub(stub)
+
+        var request = URLRequest(url: URL(string: "https://example.com/things")!)
+        request.httpMethod = "POST"
+        request.httpBody = Data(#"{"name":"x"}"#.utf8)
+
+        let (data, response) = try await makeSession().data(for: request)
+
+        XCTAssertEqual((response as? HTTPURLResponse)?.statusCode, 201)
+        XCTAssertEqual(String(data: data, encoding: .utf8), #"{"ok":true}"#)
+        XCTAssertEqual(StubURLProtocol.requestCount, 1)
+        XCTAssertEqual(StubURLProtocol.capturedRequests.first?.httpMethod, "POST")
+        XCTAssertEqual(StubURLProtocol.lastCapturedBody, Data(#"{"name":"x"}"#.utf8))
+    }
+
+    func testReplaysError() async {
+        var stub = StubURLProtocol.Stub()
+        stub.error = URLError(.notConnectedToInternet)
+        StubURLProtocol.setStub(stub)
+
+        do {
+            _ = try await makeSession().data(for: URLRequest(url: URL(string: "https://example.com")!))
+            XCTFail("expected throw")
+        } catch {
+            XCTAssertEqual((error as? URLError)?.code, .notConnectedToInternet)
+        }
+    }
+}