Support streamed response from SocketNodeInstance

src/Microsoft.AspNetCore.NodeServices/Content/Node/entrypoint-socket.js

@@ -78,14 +78,29 @@
 	            var invocation = JSON.parse(line);
 	            var invokedModule = dynamicRequire(path.resolve(process.cwd(), invocation.moduleName));
 	            var invokedFunction = invocation.exportedFunctionName ? invokedModule[invocation.exportedFunctionName] : invokedModule;
-	            // Actually invoke it, passing the callback followed by any supplied args
+	            // Prepare a callback for accepting non-streamed JSON responses
+	            var hasInvokedCallback_1 = false;
 	            var invocationCallback = function (errorValue, successValue) {
+	                if (hasInvokedCallback_1) {
+	                    throw new Error('Cannot supply more than one result. The callback has already been invoked,'
+	                        + ' or the result stream has already been accessed');
+	                }
+	                hasInvokedCallback_1 = true;
 	                connection.end(JSON.stringify({
 	                    result: successValue,
 	                    errorMessage: errorValue && (errorValue.message || errorValue),
 	                    errorDetails: errorValue && (errorValue.stack || null)
 	                }));
 	            };
+	            // Also support streamed binary responses
+	            Object.defineProperty(invocationCallback, 'stream', {
+	                enumerable: true,
+	                get: function () {
+	                    hasInvokedCallback_1 = true;
+	                    return connection;
+	                }
+	            });
+	            // Actually invoke it, passing through any supplied args
 	            invokedFunction.apply(null, [invocationCallback].concat(invocation.args));
 	        }
 	        catch (ex) {

src/Microsoft.AspNetCore.NodeServices/HostingModels/SocketNodeInstance.cs

@@ -37,19 +37,41 @@ namespace Microsoft.AspNetCore.NodeServices
             await EnsureReady();
             var virtualConnectionClient = await GetOrCreateVirtualConnectionClientAsync();
 
-            using (var virtualConnection = _currentVirtualConnectionClient.OpenVirtualConnection())
+            bool shouldDisposeVirtualConnection = true;
+            Stream virtualConnection = null;
+            try
             {
+                virtualConnection = _currentVirtualConnectionClient.OpenVirtualConnection();
+
                 // Send request
                 await WriteJsonLineAsync(virtualConnection, invocationInfo);
 
-                // Receive response
-                var response = await ReadJsonAsync<RpcResponse<T>>(virtualConnection);
-                if (response.ErrorMessage != null)
+                // Determine what kind of response format is expected
+                if (typeof(T) == typeof(Stream))
                 {
-                    throw new NodeInvocationException(response.ErrorMessage, response.ErrorDetails);
+                    // Pass through streamed binary response
+                    // It is up to the consumer to dispose this stream, so don't do so here
+                    shouldDisposeVirtualConnection = false;
+                    return (T)(object)virtualConnection;
                 }
+                else
+                {
+                    // Parse and return non-streamed JSON response
+                    var response = await ReadJsonAsync<RpcJsonResponse<T>>(virtualConnection);
+                    if (response.ErrorMessage != null)
+                    {
+                        throw new NodeInvocationException(response.ErrorMessage, response.ErrorDetails);
+                    }
 
-                return response.Result;
+                    return response.Result;
+                }
+            }
+            finally
+            {
+                if (shouldDisposeVirtualConnection)
+                {
+                    virtualConnection.Dispose();
+                }
             }
         }
 
@@ -180,7 +202,7 @@ namespace Microsoft.AspNetCore.NodeServices
         }
 
 #pragma warning disable 649 // These properties are populated via JSON deserialization
-        private class RpcResponse<TResult>
+        private class RpcJsonResponse<TResult>
         {
             public TResult Result { get; set; }
             public string ErrorMessage { get; set; }

src/Microsoft.AspNetCore.NodeServices/TypeScript/SocketNodeInstanceEntryPoint.ts

@@ -29,14 +29,32 @@ virtualConnectionServer.createInterface(server).on('connection', (connection: Du
             const invokedModule = dynamicRequire(path.resolve(process.cwd(), invocation.moduleName));
             const invokedFunction = invocation.exportedFunctionName ? invokedModule[invocation.exportedFunctionName] : invokedModule;
 
-            // Actually invoke it, passing the callback followed by any supplied args
+            // Prepare a callback for accepting non-streamed JSON responses
+            let hasInvokedCallback = false;
             const invocationCallback = (errorValue, successValue) => {
+                if (hasInvokedCallback) {
+                    throw new Error('Cannot supply more than one result. The callback has already been invoked,'
+                        + ' or the result stream has already been accessed');
+                }
+
+                hasInvokedCallback = true;
                 connection.end(JSON.stringify({
                     result: successValue,
                     errorMessage: errorValue && (errorValue.message || errorValue),
                     errorDetails: errorValue && (errorValue.stack || null)
                 }));
             };
+
+            // Also support streamed binary responses
+            Object.defineProperty(invocationCallback, 'stream', {
+                enumerable: true,
+                get: (): Duplex => {
+                    hasInvokedCallback = true;
+                    return connection;
+                }
+            });
+
+            // Actually invoke it, passing through any supplied args
             invokedFunction.apply(null, [invocationCallback].concat(invocation.args));
         } catch (ex) {
             connection.end(JSON.stringify({