Fix LastWriteTime and LastAccessTime of a symlink on Windows and Unix

src/libraries/Common/src/Interop/OSX/Interop.libc.cs

@@ -25,5 +25,7 @@ internal struct AttrList
 
         [DllImport(Libraries.libc, EntryPoint = "setattrlist", SetLastError = true)]
         internal static unsafe extern int setattrlist(string path, AttrList* attrList, void* attrBuf, nint attrBufSize, CULong options);
+
+        internal const uint FSOPT_NOFOLLOW = 0x00000001;
     }
 }

src/libraries/Native/Unix/System.Native/pal_time.c

@@ -33,7 +33,7 @@ int32_t SystemNative_UTimensat(const char* path, TimeSpec* times)
 
     updatedTimes[1].tv_sec = (time_t)times[1].tv_sec;
     updatedTimes[1].tv_nsec = (long)times[1].tv_nsec;
-    while (CheckInterrupted(result = utimensat(AT_FDCWD, path, updatedTimes, 0)));
+    while (CheckInterrupted(result = utimensat(AT_FDCWD, path, updatedTimes, AT_SYMLINK_NOFOLLOW)));
 #else
     struct timeval updatedTimes[2];
     updatedTimes[0].tv_sec = (long)times[0].tv_sec;

src/libraries/System.IO.FileSystem/tests/Base/BaseGetSetTimes.cs

@@ -23,6 +23,7 @@ public abstract class BaseGetSetTimes<T> : FileSystemTest
 
         protected abstract T GetExistingItem();
         protected abstract T GetMissingItem();
+        protected abstract T CreateSymlinkToItem(T item);
 
         protected abstract string GetItemPath(T item);
 
@@ -127,6 +128,40 @@ public void SettingUpdatesPropertiesAfterAnother()
             });
         }
 
+        [Fact]
+        [PlatformSpecific(~(TestPlatforms.Browser))] // Browser is excluded as there is only 1 effective time store.
+        public void SettingUpdatesPropertiesOnSymlink()
+        {
+            // This test is in this class since it needs all of the time functions.
+            // This test makes sure that the times are set on the symlink itself.
+            // It is needed as on OSX for example, the default for most APIs is
+            // to follow the symlink to completion and set the time on that entry
+            // instead (eg. the setattrlist will do this without the flag set).
+            // It is also the same case on unix, with the utimensat function.
+            T item = CreateSymlinkToItem(GetExistingItem());
+
+            Assert.All(TimeFunctions(requiresRoundtripping: true), (function) =>
+            {
+                // Checking that milliseconds are not dropped after setter on supported platforms.
+                DateTime dt = new DateTime(2004, 12, 9, 12, 3, 3, LowTemporalResolution ? 0 : 321, function.Kind);
+                function.Setter(item, dt);
+                DateTime result = function.Getter(item);
+                Assert.Equal(dt, result);
+                Assert.Equal(dt.ToLocalTime(), result.ToLocalTime());
+
+                // File and Directory UTC APIs treat a DateTimeKind.Unspecified as UTC whereas
+                // ToUniversalTime treats it as local.
+                if (function.Kind == DateTimeKind.Unspecified)
+                {
+                    Assert.Equal(dt, result.ToUniversalTime());
+                }
+                else
+                {
+                    Assert.Equal(dt.ToUniversalTime(), result.ToUniversalTime());
+                }
+            });
+        }
+
         [Fact]
         public void CanGetAllTimesAfterCreation()
         {

src/libraries/System.IO.FileSystem/tests/Directory/GetSetTimes.cs

@@ -51,5 +51,7 @@ public override IEnumerable<TimeFunction> TimeFunctions(bool requiresRoundtrippi
                 ((path) => Directory.GetLastWriteTimeUtc(path)),
                 DateTimeKind.Utc);
         }
+
+        protected override string CreateSymlinkToItem(string item) => Directory.CreateSymbolicLink(item + ".link", item).FullName;
     }
 }

src/libraries/System.IO.FileSystem/tests/DirectoryInfo/GetSetTimes.cs

@@ -57,5 +57,7 @@ public override IEnumerable<TimeFunction> TimeFunctions(bool requiresRoundtrippi
                 ((testDir) => testDir.LastWriteTimeUtc),
                 DateTimeKind.Utc);
         }
+
+        protected override DirectoryInfo CreateSymlinkToItem(DirectoryInfo item) => (DirectoryInfo)Directory.CreateSymbolicLink(item.FullName + ".link", item.FullName);
     }
 }

src/libraries/System.IO.FileSystem/tests/File/GetSetTimes.cs

@@ -103,6 +103,8 @@ public override IEnumerable<TimeFunction> TimeFunctions(bool requiresRoundtrippi
                 DateTimeKind.Utc);
         }
 
+        protected override string CreateSymlinkToItem(string item) => File.CreateSymbolicLink(item + ".link", item).FullName;
+
         [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotInAppContainer))] // Can't read root in appcontainer
         [PlatformSpecific(TestPlatforms.Windows)]
         public void PageFileHasTimes()

src/libraries/System.IO.FileSystem/tests/FileInfo/GetSetTimes.cs

@@ -103,6 +103,8 @@ public override IEnumerable<TimeFunction> TimeFunctions(bool requiresRoundtrippi
                 DateTimeKind.Utc);
         }
 
+        protected override FileInfo CreateSymlinkToItem(FileInfo item) => (FileInfo)File.CreateSymbolicLink(item.FullName + ".link", item.FullName);
+
         [ConditionalFact(nameof(HighTemporalResolution))]
         public void CopyToMillisecondPresent()
         {

src/libraries/System.Private.CoreLib/src/System/IO/FileStatus.SetTimes.OSX.cs

@@ -47,7 +47,7 @@ private unsafe Interop.Error SetCreationTimeCore(string path, long seconds, long
             attrList.commonAttr = Interop.libc.AttrList.ATTR_CMN_CRTIME;
 
             Interop.Error error =
-                Interop.libc.setattrlist(path, &attrList, &timeSpec, sizeof(Interop.Sys.TimeSpec), default(CULong)) == 0 ?
+                Interop.libc.setattrlist(path, &attrList, &timeSpec, sizeof(Interop.Sys.TimeSpec), new CULong(Interop.libc.FSOPT_NOFOLLOW)) == 0 ?
                 Interop.Error.SUCCESS :
                 Interop.Sys.GetLastErrorInfo().Error;
 

src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.Windows.cs

@@ -155,7 +155,7 @@ private static SafeFileHandle OpenHandle(string fullPath, bool asDirectory)
                 Interop.Kernel32.GenericOperations.GENERIC_WRITE,
                 FileShare.ReadWrite | FileShare.Delete,
                 FileMode.Open,
-                asDirectory ? Interop.Kernel32.FileOperations.FILE_FLAG_BACKUP_SEMANTICS : 0);
+                asDirectory ? (Interop.Kernel32.FileOperations.FILE_FLAG_BACKUP_SEMANTICS | Interop.Kernel32.FileOperations.FILE_FLAG_OPEN_REPARSE_POINT) : Interop.Kernel32.FileOperations.FILE_FLAG_OPEN_REPARSE_POINT);
 
             if (handle.IsInvalid)
             {