feat(dotnet): Support for JSII_DEBUG and JSII_RUNTIME (#724)

* Miscellaneous .NET runtime changes - support for JSII_DEBUG and JSII_RUNTIME

* Do not overwrite JSII_DEBUG when already passed by tests

* JSII_AGENT string enhancement with the assembly file version

* Fix integration test

* Fixing some indentation - thanks Rider

* Refactoring a return statement on NodeProccess.cs

Author: Hamza Assyad

packages/jsii-dotnet-runtime-test/test/Amazon.JSII.Runtime.IntegrationTests/ComplianceTests.cs

@@ -928,7 +928,7 @@ public void OptionalAndVariadicArgumentsTest()
         [Fact(DisplayName = Prefix + nameof(JsiiAgent))]
         public void JsiiAgent()
         {
-            Assert.Equal("DotNet/" + Environment.Version.ToString(), JsiiAgent_.JsiiAgent);
+            Assert.Equal("DotNet/" + Environment.Version.ToString() + "/.NETStandard,Version=v2.0/1.0.0.0", JsiiAgent_.JsiiAgent);
         }
 
         [Fact(DisplayName = Prefix + nameof(ReceiveInstanceOfPrivateClass))]

packages/jsii-dotnet-runtime/src/Amazon.JSII.Runtime/Services/NodeProcess.cs

@@ -1,6 +1,8 @@
 using System;
 using System.Diagnostics;
 using System.IO;
+using System.Reflection;
+using System.Runtime.Versioning;
 using Microsoft.Extensions.Logging;
 
 namespace Amazon.JSII.Runtime.Services
@@ -9,25 +11,39 @@ public class NodeProcess : INodeProcess
     {
         readonly Process _process;
         readonly ILogger _logger;
+        private const string JsiiRuntime = "JSII_RUNTIME";
+        private const string JsiiDebug = "JSII_DEBUG";
+        private const string JsiiAgent = "JSII_AGENT";
+        private const string JsiiAgentVersionString = "DotNet/{0}/{1}/{2}";
 
         public NodeProcess(IJsiiRuntimeProvider jsiiRuntimeProvider, ILoggerFactory loggerFactory)
         {
             loggerFactory = loggerFactory ?? throw new ArgumentNullException(nameof(loggerFactory));
             _logger = loggerFactory.CreateLogger<NodeProcess>();
 
+            var runtimePath = Environment.GetEnvironmentVariable(JsiiRuntime);
+            if (string.IsNullOrWhiteSpace(runtimePath))
+                runtimePath = jsiiRuntimeProvider.JsiiRuntimePath;
+            
             _process = new Process
             {
                 StartInfo = new ProcessStartInfo
                 {
                     FileName = "node",
-                    Arguments = "--max-old-space-size=4096 " + jsiiRuntimeProvider.JsiiRuntimePath,
+                    Arguments = "--max-old-space-size=4096 " + runtimePath,
                     RedirectStandardInput = true,
                     RedirectStandardOutput = true,
                     RedirectStandardError = true
                 }
             };
 
-            _process.StartInfo.EnvironmentVariables.Add("JSII_AGENT", "DotNet/" + Environment.Version);
+            var assemblyVersion = GetAssemblyFileVersion();
+            _process.StartInfo.EnvironmentVariables.Add(JsiiAgent, 
+                string.Format(JsiiAgentVersionString, Environment.Version, assemblyVersion.Item1, assemblyVersion.Item2));
+            
+            var debug = Environment.GetEnvironmentVariable(JsiiDebug);
+            if (!string.IsNullOrWhiteSpace(debug) && !_process.StartInfo.EnvironmentVariables.ContainsKey(JsiiDebug))
+                _process.StartInfo.EnvironmentVariables.Add(JsiiDebug, debug);
 
             _logger.LogDebug("Starting jsii runtime...");
             _logger.LogDebug($"{_process.StartInfo.FileName} {_process.StartInfo.Arguments}");
@@ -48,5 +64,23 @@ void IDisposable.Dispose()
             StandardError.Dispose();
             _process.Dispose();
         }
+        
+        /// <summary>
+        /// Gets the target framework attribute value and
+        /// the assembly file version for the current .NET assembly
+        /// </summary>
+        /// <returns>A tuple where Item1 is the target framework
+        /// ie .NETStandard,Version=v2.0
+        /// and item2 is the assembly file version (ie 1.0.0.0)</returns>
+        private Tuple<string, string> GetAssemblyFileVersion()
+        {
+            var assembly = typeof(NodeProcess).GetTypeInfo().Assembly;
+            var assemblyFileVersionAttribute = assembly.GetCustomAttribute(typeof(AssemblyFileVersionAttribute)) as AssemblyFileVersionAttribute;
+            var frameworkAttribute = assembly.GetCustomAttribute(typeof(TargetFrameworkAttribute)) as TargetFrameworkAttribute;
+            return new Tuple<string, string>(
+                frameworkAttribute?.FrameworkName ?? "Unknown",
+                assemblyFileVersionAttribute?.Version ?? "Unknown"
+            );
+        }
     }
 }