Cleanup unused pinvokes on unix (#9531)

* Remove TemporaryDirectory()
* Remove GetUserName()
* Use Environment.UserName on Unix
* Remove old comment
* Use Environment.UserName on Windows too

src/System.Management.Automation/CoreCLR/CorePsPlatform.cs

@@ -573,40 +573,6 @@ namespace System.Management.Automation
                 return (ErrorCategory)Unix.NativeMethods.GetErrorCategory(errno);
             }
 
-            private static string s_userName;
-            public static string UserName
-            {
-                get
-                {
-                    if (string.IsNullOrEmpty(s_userName))
-                    {
-                        s_userName = NativeMethods.GetUserName();
-                    }
-
-                    return s_userName ?? string.Empty;
-                }
-            }
-
-            public static string TemporaryDirectory
-            {
-                get
-                {
-                    // POSIX temporary directory environment variables
-                    string[] environmentVariables = { "TMPDIR", "TMP", "TEMP", "TEMPDIR" };
-                    string dir = string.Empty;
-                    foreach (string s in environmentVariables)
-                    {
-                        dir = System.Environment.GetEnvironmentVariable(s);
-                        if (!string.IsNullOrEmpty(dir))
-                        {
-                            return dir;
-                        }
-                    }
-
-                    return "/tmp";
-                }
-            }
-
             public static bool IsHardLink(ref IntPtr handle)
             {
                 // TODO:PSL implement using fstat to query inode refcount to see if it is a hard link
@@ -669,10 +635,6 @@ namespace System.Management.Automation
                 [DllImport(psLib, CharSet = CharSet.Ansi)]
                 internal static extern int GetErrorCategory(int errno);
 
-                [DllImport(psLib, CharSet = CharSet.Ansi, SetLastError = true)]
-                [return: MarshalAs(UnmanagedType.LPStr)]
-                internal static extern string GetUserName();
-
                 [DllImport(psLib)]
                 internal static extern int GetPPid(int pid);
 

src/System.Management.Automation/engine/InformationRecord.cs

@@ -101,9 +101,9 @@ namespace System.Management.Automation
                 {
                     // domain\user on Windows, just user on Unix
 #if UNIX
-                    this._user = Platform.Unix.UserName;
+                    this._user = Environment.UserName;
 #else
-                    this._user = System.Security.Principal.WindowsIdentity.GetCurrent().Name;
+                    this._user = Environment.UserDomainName + "\\" + Environment.UserName;
 #endif
                 }
 

src/System.Management.Automation/engine/InitialSessionState.cs

@@ -2768,9 +2768,9 @@ namespace System.Management.Automation.Runspaces
                 ? this.UserDriveUserName
                 // domain\user on Windows, just user on Unix
 #if UNIX
-                : Platform.Unix.UserName;
+                : Environment.UserName;
 #else
-                : System.Security.Principal.WindowsIdentity.GetCurrent().Name;
+                : Environment.UserDomainName + "_" + Environment.UserName;
 #endif
 
             // Ensure that user name contains no invalid path characters.
@@ -2781,7 +2781,7 @@ namespace System.Management.Automation.Runspaces
                 throw new PSInvalidOperationException(RemotingErrorIdStrings.InvalidUserDriveName);
             }
 
-            return userName.Replace("\\", "_");
+            return userName;
         }
 
         private Exception ProcessStartupScripts(Runspace initializedRunspace)

test/xUnit/csharp/test_CorePsPlatform.cs

@@ -36,8 +36,7 @@ namespace PSTests.Parallel
 
                 // The process should return an exit code of 0 on success
                 Assert.Equal(0, process.ExitCode);
-                // It should be the same as what our platform code returns
-                Assert.Equal(username, Platform.Unix.UserName());
+                Assert.Equal(username, Environment.UserName);
             }
         }