Making Debug and Trace behavior consistent with eachother and Desktop (#20581)

* Making Debug and Trace behavior more consistent with Desktop and eachother
* Syncs IndentLevel and IndentSize for Debug and Trace
* Completing DebugProvider APIs. Fixing Indentation bugs
* Make WriteCore public
* Make s_provider and s_indentSize volatile
* Applied PR feedbacks

4 files changed, 60 insertions, 62 deletions

diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.cs
index 433e00b2a4..3dce03af92 100644
--- a/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.cs
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/Debug.cs
@@ -11,9 +11,9 @@ namespace System.Diagnostics
     /// <summary>
     /// Provides a set of properties and methods for debugging code.
     /// </summary>
-    public static partial class Debug
+    public static class Debug
     {
-        private static DebugProvider s_provider = new DebugProvider();
+        private static volatile DebugProvider s_provider = new DebugProvider();
 
         public static DebugProvider SetProvider(DebugProvider provider)
         {
@@ -25,27 +25,32 @@ namespace System.Diagnostics
 
         public static bool AutoFlush { get { return true; } set { } }
 
+        [ThreadStatic]
+        private static int t_indentLevel;
         public static int IndentLevel
         {
             get
             {
-                return DebugProvider.IndentLevel;
+                return t_indentLevel;
             }
             set
             {
-                DebugProvider.IndentLevel = value;
+                t_indentLevel = value < 0 ? 0 : value;
+                s_provider.OnIndentLevelChanged(t_indentLevel);
             }
         }
 
+        private static volatile int s_indentSize = 4;
         public static int IndentSize
         {
             get
             {
-                return DebugProvider.IndentSize;
+                return s_indentSize;
             }
             set
             {
-                DebugProvider.IndentSize = value;
+                s_indentSize = value < 0 ? 0 : value;
+                s_provider.OnIndentSizeChanged(s_indentSize);
             }
         }
 
@@ -105,7 +110,7 @@ namespace System.Diagnostics
                 {
                     stackTrace = "";
                 }
-                WriteLine(FormatAssert(stackTrace, message, detailMessage));
+                WriteAssert(stackTrace, message, detailMessage);
                 s_provider.ShowDialog(stackTrace, message, detailMessage, "Assertion Failed");
             }
         }
@@ -123,7 +128,7 @@ namespace System.Diagnostics
                 {
                     stackTrace = "";
                 }
-                WriteLine(FormatAssert(stackTrace, message, detailMessage));
+                WriteAssert(stackTrace, message, detailMessage);
                 s_provider.ShowDialog(stackTrace, message, detailMessage, SR.GetResourceString(failureKindMessage));
             }
         }
@@ -140,15 +145,14 @@ namespace System.Diagnostics
             Assert(false, message, detailMessage);
         }
 
-        private static string FormatAssert(string stackTrace, string message, string detailMessage)
+        private static void WriteAssert(string stackTrace, string message, string detailMessage)
         {
-            string newLine = DebugProvider.GetIndentString() + Environment.NewLine;
-            return SR.DebugAssertBanner + newLine
-                   + SR.DebugAssertShortMessage + newLine
-                   + message + newLine
-                   + SR.DebugAssertLongMessage + newLine
-                   + detailMessage + newLine
-                   + stackTrace;
+            WriteLine(SR.DebugAssertBanner + Environment.NewLine
+                   + SR.DebugAssertShortMessage + Environment.NewLine
+                   + message + Environment.NewLine
+                   + SR.DebugAssertLongMessage + Environment.NewLine
+                   + detailMessage + Environment.NewLine
+                   + stackTrace);
         }
 
         [System.Diagnostics.Conditional("DEBUG")]
@@ -160,7 +164,7 @@ namespace System.Diagnostics
         [System.Diagnostics.Conditional("DEBUG")]
         public static void WriteLine(string message)
         {
-            Write(message + Environment.NewLine);
+            s_provider.WriteLine(message);
         }
 
         [System.Diagnostics.Conditional("DEBUG")]
@@ -196,7 +200,7 @@ namespace System.Diagnostics
             }
             else
             {
-                WriteLine(category + ":" + message);
+                WriteLine(category + ": " + message);
             }
         }
 
@@ -215,7 +219,7 @@ namespace System.Diagnostics
             }
             else
             {
-                Write(category + ":" + message);
+                Write(category + ": " + message);
             }
         }
 
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebugProvider.Unix.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebugProvider.Unix.cs
index b0f2f95ee4..481f309e28 100644
--- a/src/System.Private.CoreLib/shared/System/Diagnostics/DebugProvider.Unix.cs
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebugProvider.Unix.cs
@@ -38,8 +38,14 @@ namespace System.Diagnostics
             }
         }
 
-        private static void WriteCore(string message)
+        public static void WriteCore(string message)
         {
+            if (s_WriteCore != null)
+            {
+                s_WriteCore(message); 
+                return;
+            }
+
             WriteToDebugger(message);
 
             if (s_shouldWriteToStdErr)
diff --git a/src/System.Private.CoreLib/shared/System/Diagnostics/DebugProvider.cs b/src/System.Private.CoreLib/shared/System/Diagnostics/DebugProvider.cs
index 5ddb6d58ba..416423e289 100644
--- a/src/System.Private.CoreLib/shared/System/Diagnostics/DebugProvider.cs
+++ b/src/System.Private.CoreLib/shared/System/Diagnostics/DebugProvider.cs
@@ -18,21 +18,30 @@ namespace System.Diagnostics
             {
                 if (message == null)
                 {
-                    s_WriteCore(string.Empty);
+                    WriteCore(string.Empty);
                     return;
                 }
-                if (s_needIndent)
+                if (_needIndent)
                 {
                     message = GetIndentString() + message;
-                    s_needIndent = false;
+                    _needIndent = false;
                 }
-                s_WriteCore(message);
+                WriteCore(message);
                 if (message.EndsWith(Environment.NewLine))
                 {
-                    s_needIndent = true;
+                    _needIndent = true;
                 }
             }
         }
+        
+        public virtual void WriteLine(string message)
+        {
+            Write(message + Environment.NewLine);
+        }
+
+        public virtual void OnIndentLevelChanged(int indentLevel) { }
+
+        public virtual void OnIndentSizeChanged(int indentSize) { }
 
         private static readonly object s_lock = new object();
 
@@ -54,48 +63,21 @@ namespace System.Diagnostics
             }
         }
 
-        [ThreadStatic]
-        private static int s_indentLevel;
-        internal static int IndentLevel
-        {
-            get
-            {
-                return s_indentLevel;
-            }
-            set
-            {
-                s_indentLevel = value < 0 ? 0 : value;
-            }
-        }
-
-        private static int s_indentSize = 4;
-        internal static int IndentSize
-        {
-            get
-            {
-                return s_indentSize;
-            }
-            set
-            {
-                s_indentSize = value < 0 ? 0 : value;
-            }
-        }
-
-        private static bool s_needIndent;
+        private bool _needIndent = true;
 
-        private static string s_indentString;
+        private string _indentString;
 
-        internal static string GetIndentString()
+        private string GetIndentString()
         {
-            int indentCount = IndentSize * IndentLevel;
-            if (s_indentString?.Length == indentCount)
+            int indentCount = Debug.IndentSize * Debug.IndentLevel;
+            if (_indentString?.Length == indentCount)
             {
-                return s_indentString;
+                return _indentString;
             }
-            return s_indentString = new string(' ', indentCount);
+            return _indentString = new string(' ', indentCount);
         }
 
         // internal and not readonly so that the tests can swap this out.
-        internal static Action<string> s_WriteCore = WriteCore;
+        internal static Action<string> s_WriteCore;
     }
-}
+}
\ No newline at end of file
diff --git a/src/System.Private.CoreLib/src/System/Diagnostics/DebugProvider.Windows.cs b/src/System.Private.CoreLib/src/System/Diagnostics/DebugProvider.Windows.cs
index b16d30b6d5..88f6116f15 100644
--- a/src/System.Private.CoreLib/src/System/Diagnostics/DebugProvider.Windows.cs
+++ b/src/System.Private.CoreLib/src/System/Diagnostics/DebugProvider.Windows.cs
@@ -36,8 +36,14 @@ namespace System.Diagnostics
 
         private static readonly object s_ForLock = new object();
 
-        private static void WriteCore(string message)
+        public static void WriteCore(string message)
         {
+            if (s_WriteCore != null)
+            {
+                s_WriteCore(message); 
+                return;
+            }
+
             // really huge messages mess up both VS and dbmon, so we chop it up into 
             // reasonable chunks if it's too big. This is the number of characters 
             // that OutputDebugstring chunks at.