Add ProcessStartOptions class with platform-aware path resolution

src/libraries/System.Diagnostics.Process/ref/System.Diagnostics.Process.cs

@@ -261,6 +261,17 @@ public ProcessStartInfo(string fileName, System.Collections.Generic.IEnumerable<
         [System.Diagnostics.CodeAnalysis.AllowNullAttribute]
         public string WorkingDirectory { get { throw null; } set { } }
     }
+    public sealed partial class ProcessStartOptions
+    {
+        public ProcessStartOptions(string fileName) { }
+        public System.Collections.Generic.IList<string> Arguments { get { throw null; } set { } }
+        public bool CreateNewProcessGroup { get { throw null; } set { } }
+        public System.Collections.Generic.IDictionary<string, string?> Environment { get { throw null; } }
+        public string FileName { get { throw null; } }
+        public System.Collections.Generic.IList<System.Runtime.InteropServices.SafeHandle> InheritedHandles { get { throw null; } set { } }
+        public bool KillOnParentExit { get { throw null; } set { } }
+        public string? WorkingDirectory { get { throw null; } set { } }
+    }
     [System.ComponentModel.DesignerAttribute("System.Diagnostics.Design.ProcessThreadDesigner, System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")]
     public partial class ProcessThread : System.ComponentModel.Component
     {

src/libraries/System.Diagnostics.Process/src/Resources/Strings.resx

@@ -336,4 +336,7 @@
   <data name="InvalidPerfData" xml:space="preserve">
     <value>Invalid performance counter data with type '{0}'.</value>
   </data>
+  <data name="FileNotFoundResolvePath" xml:space="preserve">
+    <value>Could not resolve the file.</value>
+  </data>
 </root>

src/libraries/System.Diagnostics.Process/src/System.Diagnostics.Process.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-solaris;$(NetCoreAppCurrent)</TargetFrameworks>
@@ -26,6 +26,8 @@
     <Compile Include="System\Diagnostics\ProcessModuleCollection.cs" />
     <Compile Include="System\Diagnostics\ProcessPriorityClass.cs" />
     <Compile Include="System\Diagnostics\ProcessStartInfo.cs" />
+    <Compile Include="System\Diagnostics\ProcessStartOptions.cs" />
+    <Compile Include="System\Diagnostics\ProcessUtils.cs" />
     <Compile Include="System\Diagnostics\ProcessThread.cs" />
     <Compile Include="System\Diagnostics\ProcessThreadCollection.cs" />
     <Compile Include="System\Diagnostics\ProcessWindowStyle.cs" />
@@ -47,6 +49,8 @@
              Link="Common\System\Text\ValueStringBuilder.cs" />
     <Compile Include="$(CommonPath)System\Collections\Generic\ArrayBuilder.cs"
              Link="Common\System\Collections\Generic\ArrayBuilder.cs" />
+    <Compile Include="$(CommonPath)System\IO\StringParser.cs"
+             Link="Common\System\IO\StringParser.cs" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'windows'">
@@ -225,6 +229,7 @@
     <Compile Include="System\Diagnostics\ProcessStartInfo.Windows.cs" />
     <Compile Include="System\Diagnostics\ProcessThread.Windows.cs" />
     <Compile Include="System\Diagnostics\ProcessThreadTimes.cs" />
+    <Compile Include="System\Diagnostics\ProcessUtils.Windows.cs" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows'">
@@ -235,8 +240,7 @@
     <Compile Include="System\Diagnostics\ProcessStartInfo.Unix.cs" />
     <Compile Include="System\Diagnostics\ProcessWaitHandle.Unix.cs" />
     <Compile Include="System\Diagnostics\ProcessWaitState.Unix.cs" />
-    <Compile Include="$(CommonPath)System\IO\StringParser.cs"
-             Link="Common\System\IO\StringParser.cs" />
+    <Compile Include="System\Diagnostics\ProcessUtils.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Errors.cs"

src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.Linux.cs

@@ -108,7 +108,7 @@ private static DateTime BootTime
             ReadOnlySpan<string> allowedProgramsToRun = ["xdg-open", "gnome-open", "kfmclient"];
             foreach (var program in allowedProgramsToRun)
             {
-                string? pathToProgram = FindProgramInPath(program);
+                string? pathToProgram = ProcessUtils.FindProgramInPath(program);
                 if (!string.IsNullOrEmpty(pathToProgram))
                 {
                     return pathToProgram;

src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.SunOS.cs

@@ -38,7 +38,7 @@ internal DateTime StartTimeCore
         /// <summary>Gets execution path</summary>
         private static string? GetPathToOpenFile()
         {
-            return FindProgramInPath("xdg-open");
+            return ProcessUtils.FindProgramInPath("xdg-open");
         }
 
         /// <summary>

src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.Unix.cs

@@ -663,7 +663,7 @@ private static string[] CreateEnvp(ProcessStartInfo psi)
                 // find filename on PATH
                 else
                 {
-                    resolvedFilename = FindProgramInPath(filename);
+                    resolvedFilename = ProcessUtils.FindProgramInPath(filename);
                 }
             }
 
@@ -726,93 +726,7 @@ private static string[] CreateEnvp(ProcessStartInfo psi)
             }
 
             // Then check each directory listed in the PATH environment variables
-            return FindProgramInPath(filename);
-        }
-
-        /// <summary>
-        /// Gets the path to the program
-        /// </summary>
-        /// <param name="program"></param>
-        /// <returns></returns>
-        private static string? FindProgramInPath(string program)
-        {
-            string path;
-            string? pathEnvVar = Environment.GetEnvironmentVariable("PATH");
-            if (pathEnvVar != null)
-            {
-                var pathParser = new StringParser(pathEnvVar, ':', skipEmpty: true);
-                while (pathParser.MoveNext())
-                {
-                    string subPath = pathParser.ExtractCurrent();
-                    path = Path.Combine(subPath, program);
-                    if (IsExecutable(path))
-                    {
-                        return path;
-                    }
-                }
-            }
-            return null;
-        }
-
-        private static bool IsExecutable(string fullPath)
-        {
-            Interop.Sys.FileStatus fileinfo;
-
-            if (Interop.Sys.Stat(fullPath, out fileinfo) < 0)
-            {
-                return false;
-            }
-
-            // Check if the path is a directory.
-            if ((fileinfo.Mode & Interop.Sys.FileTypes.S_IFMT) == Interop.Sys.FileTypes.S_IFDIR)
-            {
-                return false;
-            }
-
-            const UnixFileMode AllExecute = UnixFileMode.UserExecute | UnixFileMode.GroupExecute | UnixFileMode.OtherExecute;
-
-            UnixFileMode permissions = ((UnixFileMode)fileinfo.Mode) & AllExecute;
-
-            // Avoid checking user/group when permission.
-            if (permissions == AllExecute)
-            {
-                return true;
-            }
-            else if (permissions == 0)
-            {
-                return false;
-            }
-
-            uint euid = Interop.Sys.GetEUid();
-
-            if (euid == 0)
-            {
-                return true; // We're root.
-            }
-
-            if (euid == fileinfo.Uid)
-            {
-                // We own the file.
-                return (permissions & UnixFileMode.UserExecute) != 0;
-            }
-
-            bool groupCanExecute = (permissions & UnixFileMode.GroupExecute) != 0;
-            bool otherCanExecute = (permissions & UnixFileMode.OtherExecute) != 0;
-
-            // Avoid group check when group and other have same permissions.
-            if (groupCanExecute == otherCanExecute)
-            {
-                return groupCanExecute;
-            }
-
-            if (Interop.Sys.IsMemberOfGroup(fileinfo.Gid))
-            {
-                return groupCanExecute;
-            }
-            else
-            {
-                return otherCanExecute;
-            }
+            return ProcessUtils.FindProgramInPath(filename);
         }
 
         private static long s_ticksPerSecond;