dotnet-svcutil: resolve targetFramework from Directory.Build.props (#5428)

Author: imcarolwang

src/dotnet-svcutil/lib/src/Shared/FrameworkInfo.cs

@@ -39,6 +39,7 @@ public static FrameworkInfo Parse(string fullFrameworkName)
             // framework spec form: 'netcore1.5' or 'net452'
             // framework spec form: 'net5.0'
             // framework spec form: '.NETCoreApp,Version=v6.0'
+            // framework spec form: '.NETFramework,Version=v4.8'
             for (int i = 0; i < fullFrameworkName.Length; i++)
             {
                 char c = fullFrameworkName[i];
@@ -66,13 +67,14 @@ public static FrameworkInfo Parse(string fullFrameworkName)
 
             if (name.ToLower().Contains(Netversion))
             {
-                if (version.Major >= 5)
+                //netcoreapp3.1 and lower
+                if (version.Major < 4)
                 {
-                    name = Netfx;
+                    name = Netcoreapp;
                 }
                 else
                 {
-                    name = Netcoreapp;
+                    name = Netfx;
                 }
 
                 fullFrameworkName = string.Concat(name, version.ToString());

src/dotnet-svcutil/lib/src/Shared/MSBuildProj.cs

@@ -17,6 +17,7 @@ namespace Microsoft.Tools.ServiceModel.Svcutil
 {
     internal class MSBuildProj : IDisposable
     {
+        private const string DirBuildProps = "Directory.Build.props";
         private bool _isSaved;
         private bool _ownsDirectory;
         private readonly ProjectPropertyResolver _propertyResolver;
@@ -198,10 +199,15 @@ public static async Task<MSBuildProj> ParseAsync(string projectText, string proj
                 if (targetFrameworkElements.Count() > 0)
                 {
                     // If property is specified more than once, MSBuild will resolve it by overwriting it with the last value.
-                    var targetFramework = targetFrameworkElements.Last().Value.Trim().ToLowerInvariant();
+                    var targetFramework = targetFrameworkElements.Last().Value.Trim();
                     if (!string.IsNullOrWhiteSpace(targetFramework))
                     {
-                        if(TargetFrameworkHelper.IsSupportedFramework(targetFramework, out FrameworkInfo fxInfo))
+                        if (targetFramework.ToString().StartsWith("$"))
+                        {
+                            targetFramework = GetValueFromDirBuildProps(targetFramework, msbuildProj.DirectoryPath);
+                        }
+
+                        if (TargetFrameworkHelper.IsSupportedFramework(targetFramework, out FrameworkInfo fxInfo))
                         {
                             msbuildProj._targetFrameworks.Add(targetFramework);
                         }
@@ -215,6 +221,11 @@ public static async Task<MSBuildProj> ParseAsync(string projectText, string proj
                     if (targetFrameworksElements.Count() > 0)
                     {
                         var targetFrameworks = targetFrameworksElements.Last().Value;
+                        if (targetFrameworks.ToString().StartsWith("$"))
+                        {
+                            targetFrameworks = GetValueFromDirBuildProps(targetFrameworks, msbuildProj.DirectoryPath);
+                        }
+
                         foreach (var targetFx in targetFrameworks.Split(new char[] { ';' }, StringSplitOptions.RemoveEmptyEntries).Select(p => p.Trim()))
                         {
                             if (!string.IsNullOrWhiteSpace(targetFx))
@@ -415,6 +426,27 @@ public static async Task<MSBuildProj> DotNetNewAsync(string fullPath, ILogger lo
             return project;
         }
 
+        private static string GetValueFromDirBuildProps(string elementStr, string dirPath)
+        {
+            try
+            {
+                //elementStr format: $(ElementName)
+                elementStr = elementStr.Substring(2).TrimEnd(')');
+                string filePath = Path.Combine(dirPath, DirBuildProps);
+                XDocument doc = XDocument.Load(filePath);
+                var ele = doc.Root?.Descendants(elementStr).FirstOrDefault();
+                if (ele != null)
+                {
+                    return ele.Value;
+                }
+            }
+            catch
+            {
+            }
+
+            return "";
+        }
+
         private static IEnumerable<XElement> GetGroupValues(XElement projectElement, string group, bool createOnMissing = false)
         {
             // XElement.Elements() always returns a collection, no need to check for null.