[Draft] Move Format property from TarReader to TarEntry

src/libraries/System.Formats.Tar/ref/System.Formats.Tar.cs

@@ -32,6 +32,7 @@ internal TarEntry() { }
         public int Checksum { get { throw null; } }
         public System.IO.Stream? DataStream { get { throw null; } set { } }
         public System.Formats.Tar.TarEntryType EntryType { get { throw null; } }
+        public System.Formats.Tar.TarFormat Format { get { throw null; } }
         public int Gid { get { throw null; } set { } }
         public long Length { get { throw null; } }
         public string LinkName { get { throw null; } set { } }
@@ -98,7 +99,6 @@ public enum TarFormat
     public sealed partial class TarReader : System.IDisposable
     {
         public TarReader(System.IO.Stream archiveStream, bool leaveOpen = false) { }
-        public System.Formats.Tar.TarFormat Format { get { throw null; } }
         public System.Collections.Generic.IReadOnlyDictionary<string, string>? GlobalExtendedAttributes { get { throw null; } }
         public void Dispose() { }
         public System.Formats.Tar.TarEntry? GetNextEntry(bool copyData = false) { throw null; }

src/libraries/System.Formats.Tar/src/Resources/Strings.resx

@@ -189,9 +189,6 @@
   <data name="TarDuplicateExtendedAttribute" xml:space="preserve">
     <value>The entry '{0}' has a duplicate extended attribute.</value>
   </data>
-  <data name="TarEntriesInDifferentFormats" xml:space="preserve">
-    <value>An entry in '{0}' format was found in an archive where other entries of format '{1}' have been found.</value>
-  </data>
   <data name="TarEntryBlockOrCharacterExpected" xml:space="preserve">
     <value>Cannot set the 'DeviceMajor' or 'DeviceMinor' fields on an entry that does not represent a block or character device.</value>
   </data>

src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarEntry.cs

@@ -36,6 +36,7 @@ internal TarEntry(TarEntryType entryType, string entryName, TarFormat format)
             _readerOfOrigin = null;
 
             _header = default;
+            _header._format = format;
 
             _header._extendedAttributes = new Dictionary<string, string>();
 
@@ -63,6 +64,10 @@ internal TarEntry(TarEntryType entryType, string entryName, TarFormat format)
         /// </summary>
         public TarEntryType EntryType => _header._typeFlag;
 
+        /// <summary>
+        /// The format of the entry.
+        /// </summary>
+        public TarFormat Format => _header._format;
         /// <summary>
         /// The ID of the group that owns the file represented by this entry.
         /// </summary>

src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHeader.Write.cs

@@ -33,6 +33,7 @@ internal partial struct TarHeader
         internal static void WriteGlobalExtendedAttributesHeader(Stream archiveStream, Span<byte> buffer, IEnumerable<KeyValuePair<string, string>> globalExtendedAttributes)
         {
             TarHeader geaHeader = default;
+            geaHeader._format = TarFormat.Pax;
             geaHeader._name = GenerateGlobalExtendedAttributeName();
             geaHeader._mode = (int)TarHelpers.DefaultMode;
             geaHeader._typeFlag = TarEntryType.GlobalExtendedAttributes;
@@ -88,6 +89,7 @@ internal void WriteAsPax(Stream archiveStream, Span<byte> buffer)
         {
             // First, we write the preceding extended attributes header
             TarHeader extendedAttributesHeader = default;
+            extendedAttributesHeader._format = TarFormat.Pax;
             // Fill the current header's dict
             CollectExtendedAttributesFromStandardFieldsIfNeeded();
             // And pass them to the extended attributes header for writing
@@ -129,6 +131,7 @@ private static TarHeader GetGnuLongMetadataHeader(TarEntryType entryType, string
                          (entryType is TarEntryType.LongLink && longText.Length > FieldLengths.LinkName));
 
             TarHeader longMetadataHeader = default;
+            longMetadataHeader._format = TarFormat.Gnu;
 
             longMetadataHeader._name = GnuLongMetadataName; // Same name for both longpath or longlink
             longMetadataHeader._mode = (int)TarHelpers.DefaultMode;

src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarReader.cs

@@ -41,17 +41,11 @@ public TarReader(Stream archiveStream, bool leaveOpen = false)
 
             _previouslyReadEntry = null;
             GlobalExtendedAttributes = null;
-            Format = TarFormat.Unknown;
             _isDisposed = false;
             _readFirstEntry = false;
             _reachedEndMarkers = false;
         }
 
-        /// <summary>
-        /// The format of the archive. It is initially <see cref="TarFormat.Unknown"/>. The archive format is detected after the first call to <see cref="GetNextEntry(bool)"/>.
-        /// </summary>
-        public TarFormat Format { get; private set; }
-
         /// <summary>
         /// <para>If the archive format is <see cref="TarFormat.Pax"/>, returns a read-only dictionary containing the string key-value pairs of the Global Extended Attributes in the first entry of the archive.</para>
         /// <para>If there is no Global Extended Attributes entry at the beginning of the archive, this returns an empty read-only dictionary.</para>
@@ -115,16 +109,10 @@ public void Dispose()
             {
                 if (!_readFirstEntry)
                 {
-                    Debug.Assert(Format == TarFormat.Unknown);
-                    Format = header._format;
                     _readFirstEntry = true;
                 }
-                else if (header._format != Format)
-                {
-                    throw new FormatException(string.Format(SR.TarEntriesInDifferentFormats, header._format, Format));
-                }
 
-                TarEntry entry = Format switch
+                TarEntry entry = header._format switch
                 {
                     TarFormat.Pax => new PaxTarEntry(header, this),
                     TarFormat.Gnu => new GnuTarEntry(header, this),
@@ -227,11 +215,7 @@ private bool TryGetNextEntryHeader(out TarHeader header, bool copyData)
             Debug.Assert(!_reachedEndMarkers);
 
             header = default;
-
-            // Set the initial format that is expected to be retrieved when calling TarHeader.TryReadAttributes.
-            // If the archive format is set to unknown here, it means this is the first entry we read and the value will be changed as fields get discovered.
-            // If the archive format is initially detected as pax, then any subsequent entries detected as ustar will be assumed to be pax.
-            header._format = Format;
+            header._format = TarFormat.Unknown;
 
             if (!header.TryGetNextHeader(_archiveStream, copyData))
             {
@@ -261,7 +245,6 @@ private bool TryGetNextEntryHeader(out TarHeader header, bool copyData)
                 catch (EndOfStreamException)
                 {
                     // Edge case: The only entry in the archive was a Global Extended Attributes entry
-                    Format = TarFormat.Pax;
                     return false;
                 }
                 if (header._typeFlag == TarEntryType.GlobalExtendedAttributes)
@@ -344,6 +327,7 @@ private bool TryProcessExtendedAttributesHeader(TarHeader firstHeader, bool copy
         private bool TryProcessGnuMetadataHeader(TarHeader header, bool copyData, out TarHeader finalHeader)
         {
             finalHeader = default;
+            finalHeader._format = TarFormat.Gnu;
 
             TarHeader secondHeader = default;
             secondHeader._format = TarFormat.Gnu;