Refactoring detection of spec compliant remote end in .NET

Since the W3C WebDriver working group has decided to remove the mandatory
specificationLevel capability being returned when creating a new session,
we now require a new way to detect whether a remote end uses the
open-source project dialect or the W3C dialect of the wire protocol. We
now do this by sniffing for the 'status' property in responses from the
remote end. OSS dialect responses should have it; W3C dialect responses
should not. Note that this is a potentially flawed algorithm, because
there is no requirement that a remote end cannot add additional fields to
a response body, but it's the best approach at present. If the working
group makes a change that makes it easier to identify when a W3C compliant
version of the protocol is being used, we can switch to that.

Author: jimevans

dotnet/src/webdriver/Remote/HttpCommandExecutor.cs

@@ -121,28 +121,17 @@ public virtual Response Execute(Command commandToExecute)
             }
 
             Response toReturn = this.CreateResponse(request);
-            if (commandToExecute.Name == DriverCommand.NewSession)
+            if (commandToExecute.Name == DriverCommand.NewSession && toReturn.IsSpecificationCompliant)
             {
                 // If we are creating a new session, sniff the response to determine
                 // what protocol level we are using. If the response contains a
-                // capability called "specificationLevel" that's an integer value
-                // and that's greater than 0, that means we're using the W3C protocol
-                // dialect.
+                // field called "status", it's not a spec-compliant response.
+                // Each response is polled for this, and sets a property describing
+                // whether it's using the W3C protocol dialect.
                 // TODO(jimevans): Reverse this test to make it the default path when
                 // most remote ends speak W3C, then remove it entirely when legacy
                 // protocol is phased out.
-                Dictionary<string, object> capabilities = toReturn.Value as Dictionary<string, object>;
-                if (capabilities != null)
-                {
-                    if (capabilities.ContainsKey("specificationLevel"))
-                    {
-                        int returnedSpecLevel = Convert.ToInt32(capabilities["specificationLevel"]);
-                        if (returnedSpecLevel > 0)
-                        {
-                            this.commandInfoRepository = new W3CWireProtocolCommandInfoRepository();
-                        }
-                    }
-                }
+                this.commandInfoRepository = new W3CWireProtocolCommandInfoRepository();
             }
 
             return toReturn;
@@ -198,7 +187,7 @@ private Response CreateResponse(WebRequest request)
                 string responseString = GetTextOfWebResponse(webResponse);
                 if (webResponse.ContentType != null && webResponse.ContentType.StartsWith(JsonMimeType, StringComparison.OrdinalIgnoreCase))
                 {
-                    commandResponse = Response.FromJson(responseString, this.commandInfoRepository.SpecificationLevel);
+                    commandResponse = Response.FromJson(responseString);
                 }
                 else
                 {

dotnet/src/webdriver/Remote/Response.cs

@@ -31,6 +31,7 @@ public class Response
         private object responseValue;
         private string responseSessionId;
         private WebDriverResult responseStatus;
+        private bool isSpecificationCompliant;
 
         /// <summary>
         /// Initializes a new instance of the Response class
@@ -51,7 +52,7 @@ public Response(SessionId sessionId)
             }
         }
 
-        private Response(Dictionary<string, object> rawResponse, int protocolSpecLevel)
+        private Response(Dictionary<string, object> rawResponse)
         {
             if (rawResponse.ContainsKey("sessionId"))
             {
@@ -66,13 +67,31 @@ private Response(Dictionary<string, object> rawResponse, int protocolSpecLevel)
                 this.responseValue = rawResponse["value"];
             }
 
-            if (protocolSpecLevel > 0)
+            if (rawResponse.ContainsKey("status"))
             {
+                this.responseStatus = (WebDriverResult)Convert.ToInt32(rawResponse["status"], CultureInfo.InvariantCulture);
+            }
+            else
+            {
+                // If the response does *not* have a "status" property, it
+                // is compliant with the specification, which does not put
+                // status in its responses.
+                this.isSpecificationCompliant = true;
+
                 // If the returned object does *not* have a "value" property
                 // the response value should be the entirety of the response.
                 if (!rawResponse.ContainsKey("value") && this.responseValue == null)
                 {
-                    this.responseValue = rawResponse;
+                    // Special-case for the new session command, where the "capabilities"
+                    // property of the response is the actual value we're interested in.
+                    if (rawResponse.ContainsKey("capabilities"))
+                    {
+                        this.responseValue = rawResponse["capabilities"];
+                    }
+                    else
+                    {
+                        this.responseValue = rawResponse;
+                    }
                 }
 
                 // Check for an error response by looking for an "error" property,
@@ -82,20 +101,6 @@ private Response(Dictionary<string, object> rawResponse, int protocolSpecLevel)
                     this.responseStatus = WebDriverError.ResultFromError(rawResponse["error"].ToString());
                 }
             }
-            else
-            {
-                if (rawResponse.ContainsKey("status"))
-                {
-                    this.responseStatus = (WebDriverResult)Convert.ToInt32(rawResponse["status"], CultureInfo.InvariantCulture);
-                }
-
-                // Special-case for the new session command, in the case where
-                // the remote end is using the W3C dialect of the protocol.
-                if (rawResponse.ContainsKey("capabilities"))
-                {
-                    this.responseValue = rawResponse["capabilities"];
-                }
-            }
         }
 
         /// <summary>
@@ -126,26 +131,22 @@ public WebDriverResult Status
         }
 
         /// <summary>
-        /// Returns a new <see cref="Response"/> from a JSON-encoded string.
+        /// Gets a value indicating whether this response is compliant with the WebDriver specification.
         /// </summary>
-        /// <param name="value">The JSON string to deserialize into a <see cref="Response"/>.</param>
-        /// <returns>A <see cref="Response"/> object described by the JSON string.</returns>
-        public static Response FromJson(string value)
+        public bool IsSpecificationCompliant
         {
-            return Response.FromJson(value, 0);
+            get { return this.isSpecificationCompliant; }
         }
 
         /// <summary>
         /// Returns a new <see cref="Response"/> from a JSON-encoded string.
         /// </summary>
         /// <param name="value">The JSON string to deserialize into a <see cref="Response"/>.</param>
-        /// <param name="protocolSpecLevel">The specification level of the protocol from which to
-        /// create the response.</param>
         /// <returns>A <see cref="Response"/> object described by the JSON string.</returns>
-        public static Response FromJson(string value, int protocolSpecLevel)
+        public static Response FromJson(string value)
         {
             Dictionary<string, object> deserializedResponse = JsonConvert.DeserializeObject<Dictionary<string, object>>(value, new ResponseValueJsonConverter());
-            Response response = new Response(deserializedResponse, protocolSpecLevel);
+            Response response = new Response(deserializedResponse);
             return response;
         }