Log environment-derived properties per dotnet/msbuild#7484

src/StructuredLogViewer/Entrypoint.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using System.Windows;
 using System.Windows.Threading;
 using Microsoft.Build.Logging.StructuredLogger;

src/StructuredLogger/BinaryLogger/BuildEventArgsWriter.cs

@@ -250,7 +250,14 @@ private void Write(BuildStartedEventArgs e)
         {
             Write(BinaryLogRecordKind.BuildStarted);
             WriteBuildEventArgsFields(e);
-            Write(e.BuildEnvironment);
+            if (!string.IsNullOrEmpty(Environment.GetEnvironmentVariable("MSBUILDLOGALLENVIRONMENTVARIABLES")))
+            {
+                Write(e.BuildEnvironment);
+            }
+            else
+            {
+                Write(0);
+            }
         }
 
         private void Write(BuildFinishedEventArgs e)

src/StructuredLogger/Construction/Construction.cs

@@ -80,8 +80,18 @@ public void BuildStarted(object sender, BuildStartedEventArgs args)
                 lock (syncLock)
                 {
                     Build.StartTime = args.Timestamp;
-                    var properties = Build.GetOrCreateNodeWithName<Folder>(Intern(Strings.Environment));
-                    AddProperties(properties, args.BuildEnvironment);
+                    if (args.BuildEnvironment?.Count > 0)
+                    {
+                        var properties = Build.GetOrCreateNodeWithName<Folder>(Intern(Strings.Environment));
+                        AddProperties(properties, args.BuildEnvironment);
+                    }
+                    else
+                    {
+                        Build.AddChild(new Note
+                        {
+                            Text = Intern(Strings.NoEnvironment)
+                        });
+                    }
 
                     // realize the evaluation folder now so it is ordered before the main solution node
                     _ = EvaluationFolder;

src/StructuredLogger/Construction/MessageProcessor.cs

@@ -561,7 +561,11 @@ public void AddMessage(LazyFormattedBuildEventArgs args, string message)
                 }
             }
 
-            if (nodeToAdd == null)
+            if (args is EnvironmentVariableReadEventArgs envArgs)
+            {
+                nodeToAdd = new Property { Name = Intern(envArgs.EnvironmentVariableName), Value = Intern(message) };
+            }
+            else if (nodeToAdd == null)
             {
                 message = Intern(message);
                 nodeToAdd = new Message

src/StructuredLogger/Strings/Strings.cs

@@ -446,6 +446,7 @@ public static Match IsFoundConflicts(string text)
 
         public static string Evaluation => "Evaluation";
         public static string Environment => "Environment";
+        public static string NoEnvironment => "Define a value for MSBUILDLOGALLENVIRONMENTVARIABLES to log all environment variables. Only those used in evaluating properties are currently logged.";
         public static string Imports => "Imports";
         public static string DetailedSummary => "Detailed summary";
         public static string Parameters => "Parameters";