Allow CLI UI language to be overridden by an environment variable

build_projects/dotnet-cli-build/EnvironmentVariableFilter.cs

@@ -28,6 +28,7 @@ public class EnvironmentFilter
         private IEnumerable<string> _environmentVariablesToKeep = new string []
         {
             "DOTNET_CLI_TELEMETRY_SESSIONID",
+            "DOTNET_CLI_UI_LANGUAGE",
             "DOTNET_MULTILEVEL_LOOKUP",
             "DOTNET_RUNTIME_ID",
             "DOTNET_SKIP_FIRST_TIME_EXPERIENCE",

src/Microsoft.DotNet.Cli.Utils/Product.cs

@@ -7,7 +7,7 @@ namespace Microsoft.DotNet.Cli.Utils
 {
     public class Product
     {
-        public static readonly string LongName = LocalizableStrings.DotNetCommandLineTools;
+        public static string LongName => LocalizableStrings.DotNetCommandLineTools;
         public static readonly string Version = GetProductVersion();
 
         private static string GetProductVersion()

src/dotnet/Program.cs

@@ -198,6 +198,8 @@ private static void InitializeProcess()
             // by default, .NET Core doesn't have all code pages needed for Console apps.
             // see the .NET Core Notes in https://msdn.microsoft.com/en-us/library/system.diagnostics.process(v=vs.110).aspx
             Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
+
+            UILanguageOverride.Setup();
         }
 
         internal static bool TryGetBuiltInCommand(string commandName, out BuiltInCommandMetadata builtInCommand)

src/dotnet/UILanguageOverride.cs

@@ -0,0 +1,81 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Globalization;
+
+namespace Microsoft.DotNet.Cli
+{
+    internal static class UILanguageOverride
+    {
+        private const string DOTNET_CLI_UI_LANGUAGE = nameof(DOTNET_CLI_UI_LANGUAGE);
+        private const string VSLANG = nameof(VSLANG);
+        private const string PreferredUILang = nameof(PreferredUILang);
+
+        public static void Setup()
+        {
+            CultureInfo language = GetOverriddenUILanguage();
+            if (language != null)
+            {
+                ApplyOverrideToCurrentProcess(language);
+                FlowOverrideToChildProcesses(language);
+            }
+        }
+
+        private static void ApplyOverrideToCurrentProcess(CultureInfo language)
+        {
+            CultureInfo.DefaultThreadCurrentUICulture = language;
+        }
+
+        private static void FlowOverrideToChildProcesses(CultureInfo language)
+        {
+            // Do not override any environment variables that are already set as we do not want to clobber a more granular setting with our global setting.
+            SetIfNotAlreadySet(DOTNET_CLI_UI_LANGUAGE, language.Name);
+            SetIfNotAlreadySet(VSLANG, language.LCID); // for tools following VS guidelines to just work in CLI
+            SetIfNotAlreadySet(PreferredUILang, language.Name); // for C#/VB targets that pass $(PreferredUILang) to compiler
+        }
+
+        private static CultureInfo GetOverriddenUILanguage()
+        {
+            // DOTNET_CLI_UI_LANGUAGE=<culture name> is the main way for users to customize the CLI's UI language.
+            string dotnetCliLanguage = Environment.GetEnvironmentVariable(DOTNET_CLI_UI_LANGUAGE);
+            if (dotnetCliLanguage != null)
+            {
+                try
+                {
+                    return new CultureInfo(dotnetCliLanguage);
+                }
+                catch (CultureNotFoundException) { }
+            }
+
+            // VSLANG=<lcid> is set by VS and we respect that as well so that we will respect the VS 
+            // language preference if we're invoked by VS. 
+            string vsLang = Environment.GetEnvironmentVariable(VSLANG);
+            if (vsLang != null && int.TryParse(VSLANG, out int vsLcid))
+            {
+                try
+                {
+                    return new CultureInfo(vsLcid);
+                }
+                catch (ArgumentOutOfRangeException) { }
+                catch (CultureNotFoundException) { }
+            }
+
+            return null;
+        }
+
+        private static void SetIfNotAlreadySet(string environmentVariableName, string value)
+        {
+            string currentValue = Environment.GetEnvironmentVariable(environmentVariableName);
+            if (currentValue == null)
+            {
+                Environment.SetEnvironmentVariable(environmentVariableName, value);
+            }
+        }
+
+        private static void SetIfNotAlreadySet(string environmentVariableName, int value)
+        {
+            SetIfNotAlreadySet(environmentVariableName, value.ToString());
+        }
+    }
+}

test/Microsoft.DotNet.Tools.Tests.Utilities/TestBase.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Globalization;
 using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
@@ -23,6 +24,15 @@ public abstract class TestBase : IDisposable
         private TempRoot _temp;
         private static TestAssets s_testAssets;
 
+        static TestBase()
+        {
+            // set culture of test process to match CLI sub-processes when the UI language is overriden.
+            string overriddenUILanguage = Environment.GetEnvironmentVariable("DOTNET_CLI_UI_LANGUAGE");
+            if (overriddenUILanguage != null)
+            {
+                CultureInfo.DefaultThreadCurrentUICulture = new CultureInfo(overriddenUILanguage);
+            }
+        }
 
         protected static string RepoRoot
         {

test/dotnet-new.Tests/NewCommandTests.cs

@@ -7,7 +7,7 @@
 
 namespace Microsoft.DotNet.New.Tests
 {
-    public class NewCommandTests
+    public class NewCommandTests : TestBase
     {
         [Fact]
         public void WhenSwitchIsSkippedThenItPrintsError()
@@ -16,7 +16,10 @@ public void WhenSwitchIsSkippedThenItPrintsError()
 
             cmd.ExitCode.Should().NotBe(0);
 
-            cmd.StdErr.Should().StartWith("No templates matched the input template name: Web1.1.");
+            if (!DotnetUnderTest.IsLocalized())
+            {
+                cmd.StdErr.Should().StartWith("No templates matched the input template name: Web1.1.");
+            }
         }
 
         [Fact]
@@ -26,7 +29,10 @@ public void WhenTemplateNameIsNotUniquelyMatchedThenItIndicatesProblemToUser()
 
             cmd.ExitCode.Should().NotBe(0);
 
-            cmd.StdErr.Should().StartWith("Unable to determine the desired template from the input template name: c.");
+            if (!DotnetUnderTest.IsLocalized())
+            {
+                cmd.StdErr.Should().StartWith("Unable to determine the desired template from the input template name: c.");
+            }
         }
     }
 }

test/dotnet-run.Tests/GivenDotnetRunRunsCsProj.cs

@@ -7,6 +7,8 @@
 using Microsoft.DotNet.Tools.Test.Utilities;
 using Xunit;
 
+using LocalizableStrings = Microsoft.DotNet.Tools.Run.LocalizableStrings;
+
 namespace Microsoft.DotNet.Cli.Run.Tests
 {
     public class GivenDotnetRunBuildsCsproj : TestBase
@@ -280,7 +282,7 @@ public void ItGivesAnErrorWhenAttemptingToUseALaunchProfileThatDoesNotExistWhenT
                 .ExecuteWithCapturedOutput("--launch-profile test")
                 .Should().Pass()
                          .And.HaveStdOutContaining("Hello World!")
-                         .And.HaveStdErrContaining("The specified launch profile could not be located.");
+                         .And.HaveStdErrContaining(LocalizableStrings.RunCommandExceptionCouldNotLocateALaunchSettingsFile);
         }
 
         [Fact]
@@ -368,7 +370,7 @@ public void ItGivesAnErrorWhenTheLaunchProfileNotFound()
                 .ExecuteWithCapturedOutput("--launch-profile Third")
                 .Should().Pass()
                          .And.HaveStdOutContaining("(NO MESSAGE)")
-                         .And.HaveStdErrContaining("The launch profile \"Third\" could not be applied.");
+                         .And.HaveStdErrContaining(string.Format(LocalizableStrings.RunCommandExceptionCouldNotApplyLaunchSettings, "Third", "").Trim());
         }
 
         [Fact]
@@ -396,7 +398,7 @@ public void ItGivesAnErrorWhenTheLaunchProfileCanNotBeHandled()
                 .ExecuteWithCapturedOutput("--launch-profile \"IIS Express\"")
                 .Should().Pass()
                          .And.HaveStdOutContaining("(NO MESSAGE)")
-                         .And.HaveStdErrContaining("The launch profile \"IIS Express\" could not be applied.");
+                         .And.HaveStdErrContaining(string.Format(LocalizableStrings.RunCommandExceptionCouldNotApplyLaunchSettings, "IIS Express", "").Trim());
         }
 
         [Fact]
@@ -485,7 +487,7 @@ public void ItSkipsLaunchProfilesWhenThereIsNoUsableDefault()
 
             cmd.Should().Pass()
                 .And.HaveStdOutContaining("(NO MESSAGE)")
-                .And.HaveStdErrContaining("The launch profile \"(Default)\" could not be applied.");
+                .And.HaveStdErrContaining(string.Format(LocalizableStrings.RunCommandExceptionCouldNotApplyLaunchSettings, LocalizableStrings.DefaultLaunchProfileDisplayName, "").Trim());
         }
 
         [Fact]
@@ -514,7 +516,7 @@ public void ItPrintsAnErrorWhenLaunchSettingsAreCorrupted()
 
             cmd.Should().Pass()
                 .And.HaveStdOutContaining("(NO MESSAGE)")
-                .And.HaveStdErrContaining("The launch profile \"(Default)\" could not be applied.");
+                .And.HaveStdErrContaining(string.Format(LocalizableStrings.RunCommandExceptionCouldNotApplyLaunchSettings, LocalizableStrings.DefaultLaunchProfileDisplayName, "").Trim());
         }
     }
 }

test/dotnet.Tests/ParserTests/ValdidationMessageTests.cs

@@ -11,8 +11,6 @@ namespace Microsoft.DotNet.Tests.ParserTests
 {
     public class ValidationMessageTests
     {
-        private readonly ITestOutputHelper output;
-
         [Fact]
         public void ValidationMessagesFormatCorrectly()
         {