chore: Bring in Nullable impl for Net Framework

Author: qdot

Buttplug/Core/NullableAttributes.cs

@@ -0,0 +1,193 @@
+// <copyright file="NullableAttributes.cs" company="Nonpolynomial Labs LLC">
+// Buttplug C# Source Code File - Visit https://buttplug.io for more info about the project.
+// Copyright (c) Nonpolynomial Labs LLC. All rights reserved.
+// Licensed under the BSD 3-Clause license. See LICENSE file in the project root for full license information.
+// </copyright>
+
+// Nullable reference type attributes for compatibility with older frameworks.
+// These are only used when the compiler supports nullable reference types but
+// the target framework doesn't provide these attributes.
+// See: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/attributes/nullable-analysis
+
+#if !NETSTANDARD2_1_OR_GREATER && !NETCOREAPP3_0_OR_GREATER
+
+// ReSharper disable once CheckNamespace
+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.
+    /// </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.</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.</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.</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.</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.</param>
+        public MemberNotNullAttribute(string member) => Members = new[] { member };
+
+        /// <summary>
+        /// Initializes the attribute with field or property members.
+        /// </summary>
+        /// <param name="members">The field or property members.</param>
+        public MemberNotNullAttribute(params string[] members) => Members = members;
+
+        /// <summary>
+        /// Gets the field or property members.
+        /// </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.</param>
+        /// <param name="member">The field or property member.</param>
+        public MemberNotNullWhenAttribute(bool returnValue, string member)
+        {
+            ReturnValue = returnValue;
+            Members = new[] { member };
+        }
+
+        /// <summary>
+        /// Initializes the attribute with the specified return value condition and field or property members.
+        /// </summary>
+        /// <param name="returnValue">The return value condition.</param>
+        /// <param name="members">The field or property members.</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 the field or property members.
+        /// </summary>
+        public string[] Members { get; }
+    }
+}
+
+#endif