Add netstandard2.0 support (#33)

* Add netstandard2.0 support

src/Common/Polyfills/System/Collections/Generic/CollectionExtensions.cs

@@ -0,0 +1,19 @@
+namespace System.Collections.Generic;
+
+internal static class CollectionExtensions
+{
+    public static TValue? GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key)
+    {
+        return dictionary.GetValueOrDefault(key, default!);
+    }
+
+    public static TValue GetValueOrDefault<TKey, TValue>(this IReadOnlyDictionary<TKey, TValue> dictionary, TKey key, TValue defaultValue)
+    {
+        if (dictionary is null)
+        {
+            throw new ArgumentNullException(nameof(dictionary));
+        }
+
+        return dictionary.TryGetValue(key, out TValue? value) ? value : defaultValue;
+    }
+}

src/Common/Polyfills/System/Diagnostics/CodeAnalysis/NullableAttributes.cs

@@ -0,0 +1,139 @@
+// 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
+{
+    /// <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)]
+    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)]
+    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)]
+    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)]
+    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)]
+    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)]
+    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)]
+    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)]
+    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)]
+    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; }
+    }
+
+    /// <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)]
+    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 = [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)]
+    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 field or property member 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 = [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 field and property members 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/Common/Polyfills/System/Diagnostics/CodeAnalysis/SetsRequiredMembersAttribute.cs

@@ -0,0 +1,5 @@
+namespace System.Diagnostics.CodeAnalysis
+{
+    [AttributeUsage(AttributeTargets.Constructor, AllowMultiple = false, Inherited = false)]
+    internal sealed class SetsRequiredMembersAttribute : Attribute;
+}

src/Common/Polyfills/System/Diagnostics/ProcessExtensions.cs

@@ -0,0 +1,13 @@
+// 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;
+
+internal static class ProcessExtensions
+{
+    public static void Kill(this Process process, bool entireProcessTree)
+    {
+        _ = entireProcessTree;
+        process.Kill();
+    }
+}

src/Common/Polyfills/System/IO/TextReaderExtensions.cs

@@ -0,0 +1,10 @@
+namespace System.IO;
+
+internal static class TextReaderExtensions
+{
+    public static Task<string> ReadLineAsync(this TextReader reader, CancellationToken cancellationToken)
+    {
+        _ = cancellationToken;
+        return reader.ReadLineAsync();
+    }
+}

src/Common/Polyfills/System/IO/TextWriterExtensions.cs

@@ -0,0 +1,42 @@
+using System.Runtime.InteropServices;
+
+namespace System.IO;
+
+internal static class TextWriterExtensions
+{
+    public static async Task WriteLineAsync(this TextWriter writer, ReadOnlyMemory<char> value, CancellationToken cancellationToken)
+    {
+        if (writer is null)
+        {
+            throw new ArgumentNullException(nameof(writer));
+        }
+
+        if (value.IsEmpty)
+        {
+            return;
+        }
+
+        cancellationToken.ThrowIfCancellationRequested();
+
+        if (MemoryMarshal.TryGetString(value, out string str, out int start, out int length) &&
+            start == 0 && length == str.Length)
+        {
+            await writer.WriteLineAsync(str).ConfigureAwait(false);
+        }
+        else if (MemoryMarshal.TryGetArray(value, out ArraySegment<char> array) &&
+            array.Array is not null && array.Offset == 0 && array.Count == array.Array.Length)
+        {
+            await writer.WriteLineAsync(array.Array).ConfigureAwait(false);
+        }
+        else
+        {
+            await writer.WriteLineAsync(value.ToArray()).ConfigureAwait(false);
+        }
+    }
+
+    public static async Task FlushAsync(this TextWriter writer, CancellationToken cancellationToken)
+    {
+        cancellationToken.ThrowIfCancellationRequested();
+        await writer.FlushAsync();
+    }
+}

src/Common/Polyfills/System/Net/Http/HttpClientExtensions.cs

@@ -0,0 +1,26 @@
+namespace System.Net.Http;
+
+internal static class HttpClientExtensions
+{
+    public static async Task<Stream> ReadAsStreamAsync(this HttpContent content, CancellationToken cancellationToken)
+    {
+        if (content is null)
+        {
+            throw new ArgumentNullException(nameof(content));
+        }
+
+        cancellationToken.ThrowIfCancellationRequested();
+        return await content.ReadAsStreamAsync();
+    }
+
+    public static async Task<string> ReadAsStringAsync(this HttpContent content, CancellationToken cancellationToken)
+    {
+        if (content is null)
+        {
+            throw new ArgumentNullException(nameof(content));
+        }
+
+        cancellationToken.ThrowIfCancellationRequested();
+        return await content.ReadAsStringAsync();
+    }
+}

src/Common/Polyfills/System/Runtime/CompilerServices/CompilerFeatureRequiredAttribute.cs

@@ -0,0 +1,32 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Indicates that compiler support for a particular feature is required for the location where this attribute is applied.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.All, AllowMultiple = true, Inherited = false)]
+    internal sealed class CompilerFeatureRequiredAttribute : Attribute
+    {
+        public CompilerFeatureRequiredAttribute(string featureName)
+        {
+            FeatureName = featureName;
+        }
+
+        /// <summary>
+        /// The name of the compiler feature.
+        /// </summary>
+        public string FeatureName { get; }
+
+        /// <summary>
+        /// If true, the compiler can choose to allow access to the location where this attribute is applied if it does not understand <see cref="FeatureName"/>.
+        /// </summary>
+        public bool IsOptional { get; init; }
+
+        /// <summary>
+        /// The <see cref="FeatureName"/> used for the required members C# feature.
+        /// </summary>
+        public const string RequiredMembers = nameof(RequiredMembers);
+    }
+}

src/Common/Polyfills/System/Runtime/CompilerServices/IsExternalInit.cs

@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.ComponentModel;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Reserved to be used by the compiler for tracking metadata.
+    /// This class should not be used by developers in source code.
+    /// </summary>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    internal static class IsExternalInit;
+}

src/Common/Polyfills/System/Runtime/CompilerServices/RequiredMemberAttribute.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.ComponentModel;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>Specifies that a type has required members or that a member is required.</summary>
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Field | AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    internal sealed class RequiredMemberAttribute : Attribute;
+}

src/Common/Polyfills/System/Threading/CancellationTokenSourceExtensions.cs

@@ -0,0 +1,17 @@
+using System.Text;
+
+namespace System.Threading.Tasks;
+
+internal static class CancellationTokenSourceExtensions
+{
+    public static Task CancelAsync(this CancellationTokenSource cancellationTokenSource)
+    {
+        if (cancellationTokenSource is null)
+        {
+            throw new ArgumentNullException(nameof(cancellationTokenSource));
+        }
+
+        cancellationTokenSource.Cancel();
+        return Task.CompletedTask;
+    }
+}

src/Common/Polyfills/System/Threading/Tasks/TaskExtensions.cs

@@ -0,0 +1,48 @@
+namespace System.Threading.Tasks;
+
+internal static class TaskExtensions
+{
+    public static Task WaitAsync(this Task task, CancellationToken cancellationToken)
+    {
+        return WaitAsync(task, Timeout.InfiniteTimeSpan, cancellationToken);
+    }
+
+    public static async Task<T> WaitAsync<T>(this Task<T> task, CancellationToken cancellationToken)
+    {
+        await WaitAsync(task, Timeout.InfiniteTimeSpan, cancellationToken);
+        return task.Result;
+    }
+
+    public static async Task WaitAsync(this Task task, TimeSpan timeout, CancellationToken cancellationToken)
+    {
+        if (task is null)
+        {
+            throw new ArgumentNullException(nameof(task));
+        }
+
+        if (timeout < TimeSpan.Zero && timeout != Timeout.InfiniteTimeSpan)
+        {
+            throw new ArgumentOutOfRangeException(nameof(timeout));
+        }
+
+        if (!task.IsCompleted)
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+
+            using CancellationTokenSource cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+            cts.CancelAfter(timeout);
+
+            var cancellationTask = new TaskCompletionSource<bool>();
+            using var _ = cts.Token.Register(tcs => ((TaskCompletionSource<bool>)tcs!).TrySetResult(true), cancellationTask);
+            await Task.WhenAny(task, cancellationTask.Task).ConfigureAwait(false);
+            
+            if (!task.IsCompleted)
+            {
+                cancellationToken.ThrowIfCancellationRequested();
+                throw new TimeoutException();
+            }
+        }
+
+        await task.ConfigureAwait(false);
+    }
+}