Take sessionId out of the generic response struct.

Sources/Element+Request.swift

@@ -16,7 +16,7 @@ extension Element {
     }
 
     struct ClickRequest: WebDriverRequest {
-        typealias ResponseValue = WebDriverNoResponseValue
+        typealias ResponseValue = WebDriverResponseNoValue
 
         private let element: Element
 

Sources/Session.swift

@@ -5,9 +5,12 @@ public class Session {
     let webDriver: any WebDriver
     let id: String
 
+    private var valid: Bool
+
     init(in webDriver: some WebDriver, id: String) {
         self.webDriver = webDriver
         self.id = id
+        valid = true
     }
 
     /// retryTimeout
@@ -17,23 +20,25 @@ public class Session {
     /// delete
     /// Attempts to delete the session.
     func delete() throws {
+        guard valid else {
+            return
+        }
+
         let deleteSessionRequest = DeleteSessionRequest(sessionId: id)
         try webDriver.send(deleteSessionRequest)
+        valid = false
     }
 
     deinit {
-        // TODO: Get rid of this deinit and make callers use Session.delete
-        // and handle/propegate exceptions. For now this is challenging to
-        // untangle, and unlikely to actually throw.
         do { try delete() } catch let error as WebDriverError {
-            fatalError("Error in Session.delete: \(error)")
+            assertionFailure("Error in Session.delete: \(error)")
         } catch {
-            fatalError("Unknown error in Session.delete.")
+            assertionFailure("Unknown error in Session.delete.")
         }
     }
 
     struct DeleteSessionRequest: WebDriverRequest {
-        typealias ResponseValue = WebDriverNoResponseValue
+        typealias ResponseValue = WebDriverResponseNoValue
 
         let sessionId: String
         var pathComponents: [String] { ["session", sessionId] }

Sources/WebDriverRequest.swift

@@ -1,6 +1,8 @@
 import Foundation
 import FoundationNetworking
 
+public struct CodableNone: Codable {}
+
 public protocol WebDriverRequest {
     associatedtype Body: Codable = CodableNone
     associatedtype ResponseValue: Codable = CodableNone
@@ -19,27 +21,21 @@ extension WebDriverRequest {
     public var query: [String: String] { [:] }
 }
 
-public struct CodableNone: Codable {}
-
 public enum HTTPMethod: String {
     case get = "GET"
     case delete = "DELETE"
     case post = "POST"
 }
 
-// Response to a WebDriver request
-// All fields are optional because the response returned by WebDriver might be missing them, e.g.,
-// - deleteSession request returns no sessionId and no value
-// - element click request returns a sessionId but no value
-// - etc.
+// Response to a WebDriver request with a response value.
 public struct WebDriverResponse<Value>: Codable where Value: Codable {
-    public var sessionId: String?
-    public var status: Int?
     public var value: Value?
 }
 
+// For WebDriver requests with no expected response.
 public struct WebDriverNoResponse: Codable {}
 
-public struct WebDriverNoResponseValue: Codable {
+// For WebDriver requests whose response lacks a value field.
+public struct WebDriverResponseNoValue: Codable {
     public init(from decoder: Decoder) throws {}
 }

Sources/WinAppDriver+Requests.swift

@@ -1,6 +1,10 @@
 import Foundation
 import WinSDK
 
+public struct SessionResponse: Codable {
+    public var sessionId: String
+}
+
 extension WinAppDriver {
     /// newSession(app:) - Creates a new WinAppDriver session
     /// - app: location of the exe for the app to test
@@ -11,11 +15,11 @@ extension WinAppDriver {
     public func newSession(app: String, appArguments: [String]? = nil, appWorkingDir: String? = nil, waitForAppLaunch: Int? = nil) throws -> Session {
         let args = appArguments?.joined(separator: " ")
         let newSessionRequest = NewSessionRequest(app: app, appArguments: args, appWorkingDir: appWorkingDir, waitForAppLaunch: waitForAppLaunch)
-        return Session(in: self, id: try send(newSessionRequest).sessionId!)
+        return Session(in: self, id: try send(newSessionRequest).sessionId)
     }
 
     struct NewSessionRequest: WebDriverRequest {
-        typealias ResponseValue = WebDriverNoResponseValue
+        typealias Response = SessionResponse
 
         init(app: String, appArguments: String?, appWorkingDir: String?, waitForAppLaunch: Int?) {
             body.desiredCapabilities = .init(app: app, appArguments: appArguments, appWorkingDir: appWorkingDir, waitForAppLaunch: waitForAppLaunch)
@@ -33,6 +37,7 @@ extension WinAppDriver {
             var appWorkingDir: String?
             var waitForAppLaunch: Int?
             let experimentalWebDriver = true
+
             enum CodingKeys: String, CodingKey {
                 case app
                 case appArguments
@@ -52,13 +57,13 @@ extension WinAppDriver {
     /// Creates a new session attached to an existing app top level window
     /// - Parameter appTopLevelWindowHandle: the window handle
     /// - Returns: new Session instance
-    public func newSession(appTopLevelWindowHandle: UInt) -> Session {
+    public func newSession(appTopLevelWindowHandle: UInt) throws -> Session {
         let newSessionRequest = NewSessionAttachRequest(appTopLevelWindowHandle: appTopLevelWindowHandle)
-        return Session(in: self, id: try! send(newSessionRequest).sessionId!)
+        return Session(in: self, id: try send(newSessionRequest).sessionId)
     }
 
     struct NewSessionAttachRequest: WebDriverRequest {
-        typealias ResponseValue = WebDriverNoResponseValue
+        typealias Response = SessionResponse
 
         init(appTopLevelWindowHandle: UInt) {
             let appTopLevelWindowHexHandle = String(appTopLevelWindowHandle, radix: 16)