[release/8.0-staging] Support setting ACLs on file paths longer than MAX_PATH (#113801)

* fix long path bug

* Simplify test with Math.Max

Co-authored-by: Adam Sitnik <[email protected]>

---------

Co-authored-by: Gan Keyu <[email protected]>
Co-authored-by: Keyu Gan <[email protected]>
Co-authored-by: Adam Sitnik <[email protected]>

Author: 3 people

src/libraries/System.IO.FileSystem.AccessControl/src/System/Security/AccessControl/FileSystemSecurity.cs

@@ -121,7 +121,7 @@ internal void Persist(string fullPath)
             try
             {
                 AccessControlSections persistRules = GetAccessControlSectionsFromChanges();
-                base.Persist(fullPath, persistRules);
+                base.Persist(PathInternal.EnsureExtendedPrefixIfNeeded(fullPath), persistRules);
                 OwnerModified = GroupModified = AuditRulesModified = AccessRulesModified = false;
             }
             finally

src/libraries/System.IO.FileSystem.AccessControl/tests/FileSystemAclExtensionsTests.cs

@@ -143,6 +143,25 @@ public void SetAccessControl_FileInfo_FileSecurity_Success()
             fileInfo.SetAccessControl(fileSecurity);
         }
 
+        [Fact]
+        public void SetAccessControl_FileInfo_FileSecurity_Success_NameLongerThanMaxShortPath()
+        {
+            using var directory = new TempAclDirectory();
+
+            const int MaxShortPath = 260;
+            int fileNameLength = Math.Max(MaxShortPath - directory.Path.Length, 1);
+
+            string path = Path.Combine(directory.Path, new string('1', fileNameLength) + ".txt");
+            using var file = new TempFile(path, 1);
+            var fileInfo = new FileInfo(file.Path);
+            FileSecurity fileSecurity = fileInfo.GetAccessControl(AccessControlSections.Access);
+
+            var newAccessRule = new FileSystemAccessRule(Helpers.s_NetworkServiceNTAccount, FileSystemRights.Write, AccessControlType.Allow);
+            fileSecurity.SetAccessRule(newAccessRule);
+
+            fileInfo.SetAccessControl(fileSecurity);
+        }
+
         [Fact]
         public void SetAccessControl_FileStream_FileSecurity_InvalidArguments()
         {