Use invariant culture for converting propertie's values to string

documentation/wiki/ChangeWaves.md

@@ -35,6 +35,7 @@ A wave of features is set to "rotate out" (i.e. become standard functionality) t
 - [Exec task does not trim leading whitespaces for ConsoleOutput](https://github.com/dotnet/msbuild/pull/9722)
 - [Introduce [MSBuild]::StableStringHash overloads](https://github.com/dotnet/msbuild/issues/9519)
 - [Keep the encoding of standard output & error consistent with the console code page for ToolTask](https://github.com/dotnet/msbuild/pull/9539)
+- [Convert.ToString during a property evaluation uses the InvariantCulture for all types](https://github.com/dotnet/msbuild/pull/9874)
 
 
 ### 17.8

src/Build.UnitTests/Evaluation/Expander_Tests.cs

@@ -9,6 +9,7 @@
 using System.Runtime.InteropServices;
 using System.Runtime.Versioning;
 using System.Text;
+using System.Threading;
 using System.Xml;
 using Microsoft.Build.BackEnd;
 using Microsoft.Build.Collections;
@@ -4893,5 +4894,100 @@ public void ExpandItemVectorFunctions_Exists_Directories()
                 squiggleItems.Select(i => i.EvaluatedInclude).ShouldBe(new[] { alphaBetaPath, alphaDeltaPath }, Case.Insensitive);
             }
         }
+
+        [Fact]
+        public void ExpandItem_ConvertToStringUsingInvariantCultureForNumberData()
+        {
+            var currentThread = Thread.CurrentThread;
+            var originalCulture = currentThread.CurrentCulture;
+            var originalUICulture = currentThread.CurrentUICulture;
+
+            try
+            {
+                var svSECultureInfo = new CultureInfo("sv-SE");
+                using (var env = TestEnvironment.Create())
+                {
+                    currentThread.CurrentCulture = svSECultureInfo;
+                    currentThread.CurrentUICulture = svSECultureInfo;
+                    var root = env.CreateFolder();
+
+                    var projectFile = env.CreateFile(root, ".proj",
+                        @"<Project>
+
+  <PropertyGroup>
+    <_value>$([MSBuild]::Subtract(0, 1))</_value>
+    <_otherValue Condition=""'$(_value)' &gt;= -1"">test-value</_otherValue>
+  </PropertyGroup>
+  <Target Name=""Build"" />
+</Project>");
+                    ProjectInstance projectInstance = new ProjectInstance(projectFile.Path);
+                    projectInstance.GetPropertyValue("_value").ShouldBe("-1");
+                    projectInstance.GetPropertyValue("_otherValue").ShouldBe("test-value");
+                }
+            }
+            finally
+            {
+                currentThread.CurrentCulture = originalCulture;
+                currentThread.CurrentUICulture = originalUICulture;
+            }
+        }
+
+        [Fact]
+        public void ExpandItem_ConvertToStringUsingInvariantCultureForNumberData_RespectingChangeWave()
+        {
+            // Note: Skipping the test since it is not a valid scenario when ICU mode is not used.
+            if (!ICUModeAvailable())
+            {
+                return;
+            }
+
+            var currentThread = Thread.CurrentThread;
+            var originalCulture = currentThread.CurrentCulture;
+            var originalUICulture = currentThread.CurrentUICulture;
+
+            try
+            {
+                var svSECultureInfo = new CultureInfo("sv-SE");
+                using (var env = TestEnvironment.Create())
+                {
+                    env.SetEnvironmentVariable("MSBUILDDISABLEFEATURESFROMVERSION", ChangeWaves.Wave17_10.ToString());
+                    currentThread.CurrentCulture = svSECultureInfo;
+                    currentThread.CurrentUICulture = svSECultureInfo;
+                    var root = env.CreateFolder();
+
+                    var projectFile = env.CreateFile(root, ".proj",
+                        @"<Project>
+
+  <PropertyGroup>
+    <_value>$([MSBuild]::Subtract(0, 1))</_value>
+    <_otherValue Condition=""'$(_value)' &gt;= -1"">test-value</_otherValue>
+  </PropertyGroup>
+  <Target Name=""Build"" />
+</Project>");
+                    var exception = Should.Throw<InvalidProjectFileException>(() =>
+                    {
+                        new ProjectInstance(projectFile.Path);
+                    });
+                    exception.BaseMessage.ShouldContain("A numeric comparison was attempted on \"$(_value)\"");
+                }
+            }
+            finally
+            {
+                currentThread.CurrentCulture = originalCulture;
+                currentThread.CurrentUICulture = originalUICulture;
+            }
+        }
+
+        /// <summary>
+        /// Determines if ICU mode is enabled.
+        /// Copied from: https://learn.microsoft.com/en-us/dotnet/core/extensions/globalization-icu#determine-if-your-app-is-using-icu
+        /// </summary>
+        private static bool ICUModeAvailable()
+        {
+            SortVersion sortVersion = CultureInfo.InvariantCulture.CompareInfo.Version;
+            byte[] bytes = sortVersion.SortId.ToByteArray();
+            int version = bytes[3] << 24 | bytes[2] << 16 | bytes[1] << 8 | bytes[0];
+            return version != 0 && version == sortVersion.FullVersion;
+        }
     }
 }

src/Build/Evaluation/Expander.cs

@@ -1478,7 +1478,15 @@ internal static string ConvertToString(object valueToConvert)
                 else
                 {
                     // The fall back is always to just convert to a string directly.
-                    convertedString = valueToConvert.ToString();
+                    // Issue: https://github.com/dotnet/msbuild/issues/9757
+                    if (ChangeWaves.AreFeaturesEnabled(ChangeWaves.Wave17_10))
+                    {
+                        convertedString = Convert.ToString(valueToConvert, CultureInfo.InvariantCulture);
+                    }
+                    else
+                    {
+                        convertedString = valueToConvert.ToString();
+                    }
                 }
 
                 return convertedString;