Move the LegacyFolder outside of Polly.Core

eng/Common.targets

@@ -12,4 +12,9 @@
   <ItemGroup>
     <None Include="$(MsBuildThisFileDirectory)..\Polly.png" Pack="true" PackagePath="\" />
   </ItemGroup>
+
+  <ItemGroup Condition="'$(LegacySupport)' == 'true' AND !$([MSBuild]::IsTargetFrameworkCompatible($(TargetFramework), 'netcoreapp3.1'))">
+    <Compile Include="$(MSBuildThisFileDirectory)\..\src\LegacySupport\*.cs" LinkBase="LegacySupport" />
+  </ItemGroup>
+
 </Project>

src/LegacySupport/CallerArgumentExpressionAttribute.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft Corporation. All Rights Reserved.
+
+#pragma warning disable IDE0079
+#pragma warning disable SA1101
+#pragma warning disable SA1512
+
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace System.Runtime.CompilerServices;
+
+/// <summary>
+/// Tags parameter that should be filled with specific caller name.
+/// </summary>
+[AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class CallerArgumentExpressionAttribute : Attribute
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="CallerArgumentExpressionAttribute"/> class.
+    /// </summary>
+    /// <param name="parameterName">Function parameter to take the name from.</param>
+    public CallerArgumentExpressionAttribute(string parameterName) => ParameterName = parameterName;
+
+    /// <summary>
+    /// Gets name of the function parameter that name should be taken from.
+    /// </summary>
+    public string ParameterName { get; }
+}

src/LegacySupport/IsExternalInit.cs

@@ -0,0 +1,12 @@
+// Copyright (c) Microsoft Corporation. All Rights Reserved.
+
+#pragma warning disable IDE0079
+#pragma warning disable S3903
+
+/* This enables support for C# 9/10 records on older frameworks */
+
+namespace System.Runtime.CompilerServices;
+
+internal static class IsExternalInit
+{
+}

src/LegacySupport/NullableAttributes.cs

@@ -0,0 +1,179 @@
+// Copyright (c) Microsoft Corporation. All Rights Reserved.
+
+#pragma warning disable IDE0079
+#pragma warning disable IDE0079
+#pragma warning disable SA1101
+#pragma warning disable SA1116
+#pragma warning disable SA1117
+#pragma warning disable SA1402
+#pragma warning disable SA1512
+#pragma warning disable SA1623
+#pragma warning disable SA1642
+#pragma warning disable SA1623
+#pragma warning disable SA1642
+#pragma warning disable SA1649
+#pragma warning disable S3903
+#pragma warning disable IDE0021 // Use block body for constructors
+#pragma warning disable CA1019
+
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Diagnostics.CodeAnalysis;
+
+#if !NETCOREAPP3_1_OR_GREATER
+/// <summary>Specifies that null is allowed as an input even if the corresponding type disallows it.</summary>
+[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class AllowNullAttribute : Attribute
+{
+}
+
+/// <summary>Specifies that null is disallowed as an input even if the corresponding type allows it.</summary>
+[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class DisallowNullAttribute : Attribute
+{
+}
+
+/// <summary>Specifies that an output may be null even if the corresponding type disallows it.</summary>
+[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class MaybeNullAttribute : Attribute
+{
+}
+
+/// <summary>Specifies that an output will not be null even if the corresponding type allows it. Specifies that an input argument was not null when the call returns.</summary>
+[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class NotNullAttribute : Attribute
+{
+}
+
+/// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter may be null even if the corresponding type disallows it.</summary>
+[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class MaybeNullWhenAttribute : Attribute
+{
+    /// <summary>Initializes the attribute with the specified return value condition.</summary>
+    /// <param name="returnValue">
+    /// The return value condition. If the method returns this value, the associated parameter may be null.
+    /// </param>
+    public MaybeNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;
+
+    /// <summary>Gets the return value condition.</summary>
+    public bool ReturnValue { get; }
+}
+
+/// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter will not be null even if the corresponding type allows it.</summary>
+[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class NotNullWhenAttribute : Attribute
+{
+    /// <summary>Initializes the attribute with the specified return value condition.</summary>
+    /// <param name="returnValue">
+    /// The return value condition. If the method returns this value, the associated parameter will not be null.
+    /// </param>
+    public NotNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;
+
+    /// <summary>Gets the return value condition.</summary>
+    public bool ReturnValue { get; }
+}
+
+/// <summary>Specifies that the output will be non-null if the named parameter is non-null.</summary>
+[AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, AllowMultiple = true, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class NotNullIfNotNullAttribute : Attribute
+{
+    /// <summary>Initializes the attribute with the associated parameter name.</summary>
+    /// <param name="parameterName">
+    /// The associated parameter name.  The output will be non-null if the argument to the parameter specified is non-null.
+    /// </param>
+    public NotNullIfNotNullAttribute(string parameterName) => ParameterName = parameterName;
+
+    /// <summary>Gets the associated parameter name.</summary>
+    public string ParameterName { get; }
+}
+
+/// <summary>Applied to a method that will never return under any circumstance.</summary>
+[AttributeUsage(AttributeTargets.Method, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class DoesNotReturnAttribute : Attribute
+{
+}
+
+/// <summary>Specifies that the method will not return if the associated Boolean parameter is passed the specified value.</summary>
+[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+[ExcludeFromCodeCoverage]
+internal sealed class DoesNotReturnIfAttribute : Attribute
+{
+    /// <summary>Initializes the attribute with the specified parameter value.</summary>
+    /// <param name="parameterValue">
+    /// The condition parameter value. Code after the method will be considered unreachable by diagnostics if the argument to
+    /// the associated parameter matches this value.
+    /// </param>
+    public DoesNotReturnIfAttribute(bool parameterValue) => ParameterValue = parameterValue;
+
+    /// <summary>Gets the condition parameter value.</summary>
+    public bool ParameterValue { get; }
+}
+#endif
+
+/// <summary>Specifies that the method or property will ensure that the listed field and property members have not-null values.</summary>
+[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
+[ExcludeFromCodeCoverage]
+internal sealed class MemberNotNullAttribute : Attribute
+{
+    /// <summary>Initializes the attribute with a field or property member.</summary>
+    /// <param name="member">
+    /// The field or property member that is promised to be not-null.
+    /// </param>
+    public MemberNotNullAttribute(string member) => Members = new[] { member };
+
+    /// <summary>Initializes the attribute with the list of field and property members.</summary>
+    /// <param name="members">
+    /// The list of field and property members that are promised to be not-null.
+    /// </param>
+    public MemberNotNullAttribute(params string[] members) => Members = members;
+
+    /// <summary>Gets field or property member names.</summary>
+    public string[] Members { get; }
+}
+
+/// <summary>Specifies that the method or property will ensure that the listed field and property members have not-null values when returning with the specified return value condition.</summary>
+[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
+[ExcludeFromCodeCoverage]
+internal sealed class MemberNotNullWhenAttribute : Attribute
+{
+    /// <summary>Initializes the attribute with the specified return value condition and a field or property member.</summary>
+    /// <param name="returnValue">
+    /// The return value condition. If the method returns this value, the associated parameter will not be null.
+    /// </param>
+    /// <param name="member">
+    /// The field or property member that is promised to be not-null.
+    /// </param>
+    public MemberNotNullWhenAttribute(bool returnValue, string member)
+    {
+        ReturnValue = returnValue;
+        Members = new[] { member };
+    }
+
+    /// <summary>Initializes the attribute with the specified return value condition and list of field and property members.</summary>
+    /// <param name="returnValue">
+    /// The return value condition. If the method returns this value, the associated parameter will not be null.
+    /// </param>
+    /// <param name="members">
+    /// The list of field and property members that are promised to be not-null.
+    /// </param>
+    public MemberNotNullWhenAttribute(bool returnValue, params string[] members)
+    {
+        ReturnValue = returnValue;
+        Members = members;
+    }
+
+    /// <summary>Gets the return value condition.</summary>
+    public bool ReturnValue { get; }
+
+    /// <summary>Gets field or property member names.</summary>
+    public string[] Members { get; }
+}

src/Polly.Core/Builder/ResilienceStrategyBuilder.cs

@@ -111,16 +111,5 @@ private ResilienceStrategy CreateResilienceStrategy(Entry entry)
         return entry.Factory(context);
     }
 
-    private sealed class Entry
-    {
-        public Entry(Func<ResilienceStrategyBuilderContext, ResilienceStrategy> factory, ResilienceStrategyOptions properties)
-        {
-            Factory = factory;
-            Properties = properties;
-        }
-
-        public Func<ResilienceStrategyBuilderContext, ResilienceStrategy> Factory { get; }
-
-        public ResilienceStrategyOptions Properties { get; }
-    }
+    private sealed record Entry(Func<ResilienceStrategyBuilderContext, ResilienceStrategy> Factory, ResilienceStrategyOptions Properties);
 }

src/Polly.Core/Polly.Core.csproj

@@ -10,6 +10,7 @@
     <UseDefaultAnalyzers>true</UseDefaultAnalyzers>
     <SkipPollyUsings>true</SkipPollyUsings>
     <MutationScore>100</MutationScore>
+    <LegacySupport>true</LegacySupport>
   </PropertyGroup>
 
   <ItemGroup>

src/Polly.sln

@@ -30,6 +30,7 @@ EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "eng", "eng", "{04E3C7C5-31F7-4CD6-8BEC-C1032527D231}"
 	ProjectSection(SolutionItems) = preProject
 		..\eng\Analyzers.targets = ..\eng\Analyzers.targets
+		..\eng\Common.targets = ..\eng\Common.targets
 		..\eng\Library.targets = ..\eng\Library.targets
 		..\eng\Test.targets = ..\eng\Test.targets
 	EndProjectSection