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/Common/pal_config.h.in

@@ -112,6 +112,7 @@
 #cmakedefine01 HAVE_GETDOMAINNAME
 #cmakedefine01 HAVE_UNAME
 #cmakedefine01 HAVE_UTIMENSAT
+#cmakedefine01 HAVE_LUTIMES
 #cmakedefine01 HAVE_FUTIMES
 #cmakedefine01 HAVE_FUTIMENS
 #cmakedefine01 HAVE_MKSTEMPS

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

@@ -33,7 +33,15 @@ 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)));
+#elif HAVE_LUTIMES
+    struct timeval updatedTimes[2];
+    updatedTimes[0].tv_sec = (long)times[0].tv_sec;
+    updatedTimes[0].tv_usec = (int)times[0].tv_nsec / 1000;
+
+    updatedTimes[1].tv_sec = (long)times[1].tv_sec;
+    updatedTimes[1].tv_usec = (int)times[1].tv_nsec / 1000;
+    while (CheckInterrupted(result = lutimes(path, updatedTimes)));
 #else
     struct timeval updatedTimes[2];
     updatedTimes[0].tv_sec = (long)times[0].tv_sec;

src/libraries/Native/Unix/configure.cmake

@@ -683,6 +683,11 @@ check_symbol_exists(
     sys/stat.h
     HAVE_UTIMENSAT)
 
+check_symbol_exists(
+    lutimes
+    sys/time.h
+    HAVE_LUTIMES)
+
 set (PREVIOUS_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
 set (CMAKE_REQUIRED_FLAGS "-Werror -Wsign-conversion")
 

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

@@ -24,6 +24,17 @@ public abstract class BaseGetSetTimes<T> : FileSystemTest
         protected abstract T GetExistingItem();
         protected abstract T GetMissingItem();
 
+        protected abstract T CreateSymlink(string path, string pathToTarget);
+
+        protected T CreateSymlinkToItem(T item, bool isRelative)
+        {
+            // Creates a Symlink to 'item' (may or may not exist) that is optionally
+            // a relative path rather than an absolute path.
+            string itemPath = GetItemPath(item);
+            string target = isRelative ? Path.GetFileName(itemPath) : itemPath;
+            return CreateSymlink(itemPath + ".link", target);
+        }
+
         protected abstract string GetItemPath(T item);
 
         public abstract IEnumerable<TimeFunction> TimeFunctions(bool requiresRoundtripping = false);
@@ -43,11 +54,8 @@ public static TimeFunction Create(SetTime setter, GetTime getter, DateTimeKind k
             public DateTimeKind Kind => Item3;
         }
 
-        [Fact]
-        public void SettingUpdatesProperties()
+        private void SettingUpdatesPropertiesCore(T item)
         {
-            T item = GetExistingItem();
-
             Assert.All(TimeFunctions(requiresRoundtripping: true), (function) =>
             {
                 // Checking that milliseconds are not dropped after setter.
@@ -71,6 +79,56 @@ public void SettingUpdatesProperties()
             });
         }
 
+        [Fact]
+        public void SettingUpdatesProperties()
+        {
+            T item = GetExistingItem();
+            SettingUpdatesPropertiesCore(item);
+        }
+
+        [Theory]
+        [PlatformSpecific(~TestPlatforms.Browser)] // Browser is excluded as it doesn't support symlinks
+        [InlineData(false, false)]
+        [InlineData(false, true)]
+        [InlineData(true, false)]
+        [InlineData(true, true)]
+        public void SettingUpdatesPropertiesOnSymlink(bool targetIsRelative, bool targetExists)
+        {
+            // 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.
+            // It is a theory since there are variants which have a relative target
+            // or absolute target, and whether the target exists or not.
+
+            T target = targetExists ? GetExistingItem() : GetMissingItem();
+
+            // When the target exists, we want to verify that its times don't change.
+
+            T link = CreateSymlinkToItem(target, targetIsRelative);
+            if (!targetExists)
+            {
+                SettingUpdatesPropertiesCore(link);
+            }
+            else
+            {
+                // Get the target's initial times
+                IEnumerable<TimeFunction> timeFunctions = TimeFunctions(requiresRoundtripping: true);
+                DateTime[] initialTimes = timeFunctions.Select((funcs) => funcs.Getter(target)).ToArray();
+
+                SettingUpdatesPropertiesCore(link);
+
+                // Ensure that we have the latest times.
+                if (target is FileSystemInfo fsi) fsi.Refresh();
+
+                // Ensure the target's times haven't changed.
+                DateTime[] updatedTimes = timeFunctions.Select((funcs) => funcs.Getter(target)).ToArray();
+                Assert.Equal(initialTimes, updatedTimes);
+            }
+        }
+
         [Fact]
         [PlatformSpecific(~TestPlatforms.Browser)] // Browser is excluded as there is only 1 effective time store.
         public void SettingUpdatesPropertiesAfterAnother()

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

@@ -9,6 +9,8 @@ public class Directory_GetSetTimes : StaticGetSetTimes
     {
         protected override string GetExistingItem() => Directory.CreateDirectory(GetTestFilePath()).FullName;
 
+        protected override string CreateSymlink(string path, string pathToTarget) => Directory.CreateSymbolicLink(path, pathToTarget).FullName;
+
         public override IEnumerable<TimeFunction> TimeFunctions(bool requiresRoundtripping = false)
         {
             if (IOInputs.SupportsGettingCreationTime && (!requiresRoundtripping || IOInputs.SupportsSettingCreationTime))

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

@@ -11,6 +11,8 @@ public class DirectoryInfo_GetSetTimes : InfoGetSetTimes<DirectoryInfo>
 
         protected override DirectoryInfo GetMissingItem() => new DirectoryInfo(GetTestFilePath());
 
+        protected override DirectoryInfo CreateSymlink(string path, string pathToTarget) => (DirectoryInfo)Directory.CreateSymbolicLink(path, pathToTarget);
+
         protected override string GetItemPath(DirectoryInfo item) => item.FullName;
 
         protected override void InvokeCreate(DirectoryInfo item) => item.Create();

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

@@ -22,6 +22,8 @@ protected override string GetExistingItem()
             return path;
         }
 
+        protected override string CreateSymlink(string path, string pathToTarget) => File.CreateSymbolicLink(path, pathToTarget).FullName;
+
         [Fact]
         [PlatformSpecific(TestPlatforms.Linux)]
         public void BirthTimeIsNotNewerThanLowestOfAccessModifiedTimes()

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

@@ -17,6 +17,8 @@ protected override FileInfo GetExistingItem()
             return new FileInfo(path);
         }
 
+        protected override FileInfo CreateSymlink(string path, string pathToTarget) => (FileInfo)File.CreateSymbolicLink(path, pathToTarget);
+
         private static bool HasNonZeroNanoseconds(DateTime dt) => dt.Ticks % 10 != 0;
 
         public FileInfo GetNonZeroMilliseconds()

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

@@ -150,12 +150,18 @@ private static SafeFileHandle OpenHandle(string fullPath, bool asDirectory)
                 throw new ArgumentException(SR.Arg_PathIsVolume, "path");
             }
 
+            int dwFlagsAndAttributes = Interop.Kernel32.FileOperations.FILE_FLAG_OPEN_REPARSE_POINT;
+            if (asDirectory)
+            {
+                dwFlagsAndAttributes |= Interop.Kernel32.FileOperations.FILE_FLAG_BACKUP_SEMANTICS;
+            }
+
             SafeFileHandle handle = Interop.Kernel32.CreateFile(
                 fullPath,
                 Interop.Kernel32.GenericOperations.GENERIC_WRITE,
                 FileShare.ReadWrite | FileShare.Delete,
                 FileMode.Open,
-                asDirectory ? Interop.Kernel32.FileOperations.FILE_FLAG_BACKUP_SEMANTICS : 0);
+                dwFlagsAndAttributes);
 
             if (handle.IsInvalid)
             {