Restore the manual Tracer.ctor so that it works in version-conflict s…

…cenarios

tracer/src/Datadog.Trace.Manual/Tracer.cs

@@ -3,6 +3,7 @@
 // This product includes software developed at Datadog (https://www.datadoghq.com/). Copyright 2017 Datadog, Inc.
 // </copyright>
 
+using Datadog.Trace.ClrProfiler.AutoInstrumentation.ManualInstrumentation;
 using Datadog.Trace.Configuration;
 using Datadog.Trace.DuckTyping;
 using Datadog.Trace.SourceGenerators;
@@ -20,9 +21,22 @@ public sealed class Tracer : ITracer, IDatadogOpenTracingTracer
         private object? _automaticSettings;
         private ImmutableTracerSettings? _settings;
 
-        private Tracer(object? automaticTracer)
+        [Instrumented] // This is only _actually_ instrumented up to 3.6.0 (automatic)
+        private Tracer(object? automaticTracer, Dictionary<string, object?> initialValues)
         {
             AutomaticTracer = automaticTracer;
+
+            // In 3.7.0+ we don't bother populating the dictionary with the settings
+            // seeing as the whole _settings object is going to be thrown away and
+            // repopulated if the customer calls Settings. Kind of annoying...
+            // so to avoid the extra work/allocation we check whether the initial values contains the
+            // agent key, as an easy way of detecting if we're running in this version-conflict mode.
+            // If we're not in version conflict, we can delay allocating the settings object until
+            // its actually requested.
+            if (initialValues.ContainsKey(TracerSettingKeyConstants.AgentUriKey))
+            {
+                _settings = new ImmutableTracerSettings(initialValues);
+            }
         }
 
         // Not null when the automatic tracer is available
@@ -49,7 +63,7 @@ public static Tracer Instance
 
                 // need a new tracer instance, because either the automatic tracer has changed
                 // or this is the first time fetching it
-                var instance = new Tracer(automaticTracer);
+                var instance = new Tracer(automaticTracer, new());
                 _instance = instance;
                 return instance;
             }
@@ -141,7 +155,12 @@ private static void Configure(Dictionary<string, object?> settings)
         /// settings, only if the ImmutableTracerSettings (automatic) provided is different to the current one.
         /// </summary>
         [Instrumented]
-        private Dictionary<string, object?>? GetUpdatedImmutableTracerSettings(object? automaticTracer, ref object? automaticSettings) => null;
+        private Dictionary<string, object?>? GetUpdatedImmutableTracerSettings(object? automaticTracer, ref object? automaticSettings)
+        {
+            _ = automaticTracer;
+            _ = automaticSettings;
+            return null;
+        }
 
         /// <summary>
         /// Automatic instrumentation intercepts this method and returns a duck-typed Scope from Datadog.Trace.

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/ManualInstrumentation/Tracer/CtorIntegration.cs

@@ -32,6 +32,8 @@ public class CtorIntegration
 {
     internal static CallTargetState OnMethodBegin<TTarget>(TTarget instance, object? automaticTracer, Dictionary<string, object?> values)
     {
+        // In earlier versions of the automatic tracer, the settings were passed in as a dictionary
+        // but in 3.7.0 we don't need to instrument them
         if (automaticTracer is Datadog.Trace.Tracer tracer)
         {
             PopulateSettings(values, tracer.Settings);
@@ -43,6 +45,7 @@ internal static CallTargetState OnMethodBegin<TTarget>(TTarget instance, object?
     internal static void PopulateSettings(Dictionary<string, object?> values, ImmutableTracerSettings settings)
     {
         // record all the settings in the dictionary
+        // This key is used to detect if the settings have been populated _at all_, so should always be sent
         values[TracerSettingKeyConstants.AgentUriKey] = settings.ExporterInternal.AgentUriInternal;
 #pragma warning disable CS0618 // Type or member is obsolete
         values[TracerSettingKeyConstants.AnalyticsEnabledKey] = settings.AnalyticsEnabledInternal;

tracer/src/Datadog.Trace/ClrProfiler/AutoInstrumentation/ManualInstrumentation/Tracer/GetUpdatedImmutableTracerSettingsIntegration.cs

@@ -20,7 +20,7 @@ namespace Datadog.Trace.ClrProfiler.AutoInstrumentation.ManualInstrumentation.Tr
     MethodName = "GetUpdatedImmutableTracerSettings",
     ReturnTypeName = "System.Collections.Generic.Dictionary`2[System.String,System.Object]",
     ParameterTypeNames = [ClrNames.Object, "System.Object&"],
-    MinimumVersion = "3.6.*", // added in 3.7.0
+    MinimumVersion = "3.7.0", // added in 3.7.0
     MaximumVersion = ManualInstrumentationConstants.MaxVersion,
     IntegrationName = ManualInstrumentationConstants.IntegrationName)]
 [Browsable(false)]

tracer/test/Datadog.Trace.Tests/ManualInstrumentation/InstrumentationTests.cs

@@ -23,13 +23,9 @@ public void DatadogTraceManual_AllInstrumentedMethodsAreDecoratedWithInstrumente
     {
         var manualAssembly = typeof(T).Assembly;
         var assemblyName = manualAssembly.GetName().Name;
-        var assemblyVersion = manualAssembly.GetName().Version!;
 
         // find all types in Datadog.Trace that instrument methods in the target assembly
-        // exclude the ones that don't target older versions
-        var instrumentations = GetAllInstrumentations(assemblyName)
-                              .Where(x => GetMaxVersion(x.Attribute.MaximumVersion) >= assemblyVersion)
-                              .GroupBy(x => x.Attribute.TypeName);
+        var instrumentations = GetAllInstrumentations(assemblyName).GroupBy(x => x.Attribute.TypeName);
 
         var attributedMembers = manualAssembly
                                .GetTypes()
@@ -97,27 +93,6 @@ private static Type GetType(string type, Assembly targetAssembly)
                               : x.Attribute.AssemblyName == assemblyName);
     }
 
-    private static Version GetMaxVersion(string version)
-    {
-        // handle our version numbers with * etc
-        var splits = version.Split('.');
-        var major = splits.Length > 0 ? ToVersion(splits[0]) : ushort.MaxValue;
-        var minor = splits.Length > 1 ? ToVersion(splits[1]) : ushort.MaxValue;
-        var patch = splits.Length > 2 ? ToVersion(splits[2]) : ushort.MaxValue;
-
-        return new Version(major, minor, patch);
-
-        static ushort ToVersion(string number)
-        {
-            if (!string.IsNullOrEmpty(number) && ushort.TryParse(number, out var value))
-            {
-                return value;
-            }
-
-            return ushort.MaxValue;
-        }
-    }
-
     private static bool IsTarget(MemberInfo memberInfo, string methodName, List<Type> expectedParams)
     {
         if (memberInfo.Name != methodName)