Merge pull request #24398 from sharwell/use-culture-attribute

Add UseCultureAttribute to help with culture-dependent unit tests

src/Test/Utilities/Portable/Assert/UseCultureAttribute.cs

+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using System;
+using System.Globalization;
+using System.Reflection;
+using System.Threading;
+using Xunit.Sdk;
+
+namespace Roslyn.Test.Utilities
+{
+    /// <summary>
+    /// Apply this attribute to your test method to replace the
+    /// <see cref="Thread.CurrentThread" /> <see cref="CultureInfo.CurrentCulture" /> and
+    /// <see cref="CultureInfo.CurrentUICulture" /> with another culture.
+    /// </summary>
+    /// <remarks>
+    /// This code was adapted from
+    /// https://github.com/xunit/samples.xunit/blob/5de2967/UseCulture/UseCultureAttribute.cs.
+    /// The original code is (c) 2014 Outercurve Foundation and licensed under the Apache License,
+    /// Version 2.0.
+    /// </remarks>
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+    public class UseCultureAttribute : BeforeAfterTestAttribute
+    {
+        private readonly Lazy<CultureInfo> _culture;
+        private readonly Lazy<CultureInfo> _uiCulture;
+        private CultureInfo _originalCulture;
+        private CultureInfo _originalUICulture;
+
+        /// <summary>
+        /// Replaces the culture and UI culture of the current thread with
+        /// <paramref name="culture" />
+        /// </summary>
+        /// <param name="culture">The name of the culture.</param>
+        /// <remarks>
+        /// <para>
+        /// This constructor overload uses <paramref name="culture" /> for both
+        /// <see cref="Culture" /> and <see cref="UICulture" />.
+        /// </para>
+        /// </remarks>
+        public UseCultureAttribute(string culture)
+            : this(culture, culture)
+        {
+        }
+
+        /// <summary>
+        /// Replaces the culture and UI culture of the current thread with
+        /// <paramref name="culture" /> and <paramref name="uiCulture" />
+        /// </summary>
+        /// <param name="culture">The name of the culture.</param>
+        /// <param name="uiCulture">The name of the UI culture.</param>
+        public UseCultureAttribute(string culture, string uiCulture)
+        {
+#if NET46 || NET461
+            _culture = new Lazy<CultureInfo>(() => new CultureInfo(culture, useUserOverride: false));
+            _uiCulture = new Lazy<CultureInfo>(() => new CultureInfo(uiCulture, useUserOverride: false));
+#elif NETCOREAPP2_0
+            _culture = new Lazy<CultureInfo>(() => new CultureInfo(culture));
+            _uiCulture = new Lazy<CultureInfo>(() => new CultureInfo(uiCulture));
+#else
+            _culture = new Lazy<CultureInfo>(() => throw new NotSupportedException());
+            _uiCulture = new Lazy<CultureInfo>(() => throw new NotSupportedException());
+#endif
+        }
+
+        /// <summary>
+        /// Gets the culture.
+        /// </summary>
+        public CultureInfo Culture => _culture.Value;
+
+        /// <summary>
+        /// Gets the UI culture.
+        /// </summary>
+        public CultureInfo UICulture => _uiCulture.Value;
+
+        /// <summary>
+        /// Stores the current <see cref="CultureInfo.CurrentCulture" /> and <see cref="CultureInfo.CurrentUICulture" />
+        /// and replaces them with the new cultures defined in the constructor.
+        /// </summary>
+        /// <param name="methodUnderTest">The method under test</param>
+        public override void Before(MethodInfo methodUnderTest)
+        {
+            _originalCulture = CultureInfo.CurrentCulture;
+            _originalUICulture = CultureInfo.CurrentUICulture;
+
+#if NET46 || NET461 || NETCOREAPP2_0
+            CultureInfo.CurrentCulture = Culture;
+            CultureInfo.CurrentUICulture = UICulture;
+
+#if NET46 || NET461
+            CultureInfo.CurrentCulture.ClearCachedData();
+            CultureInfo.CurrentUICulture.ClearCachedData();
+#endif
+#else
+            throw new NotSupportedException("Cannot set the current culture on this framework target.");
+#endif
+        }
+
+        /// <summary>
+        /// Restores the original <see cref="CultureInfo.CurrentCulture" /> and
+        /// <see cref="CultureInfo.CurrentUICulture" />.
+        /// </summary>
+        /// <param name="methodUnderTest">The method under test</param>
+        public override void After(MethodInfo methodUnderTest)
+        {
+#if NET46 || NET461 || NETCOREAPP2_0
+            CultureInfo.CurrentCulture = _originalCulture;
+            CultureInfo.CurrentUICulture = _originalUICulture;
+
+#if NET46 || NET461
+            CultureInfo.CurrentCulture.ClearCachedData();
+            CultureInfo.CurrentUICulture.ClearCachedData();
+#endif
+#else
+            throw new NotSupportedException("Cannot set the current culture on this framework target.");
+#endif
+        }
+    }
+}