Add Polysharp and adjustments that do not break legacy frameworks

AGENTS.md

@@ -204,6 +204,7 @@ SharpCompress supports multiple archive and compression formats:
 - Preserve existing public method signatures and behavior when possible.
 - If a breaking change is unavoidable, document it and provide a migration path.
 - Add or update tests that cover backward compatibility expectations.
+- Avoid exposing public `init` setters, positional records, `required` members, or other metadata that forces consumers onto newer C# language versions; validate older-consumer compatibility with tests when changing exported APIs.
 
 ### Stream Ownership and Position Checklist
 - Verify `LeaveStreamOpen` behavior for externally owned streams.

Directory.Packages.props

@@ -18,5 +18,6 @@
       Include="Microsoft.VisualStudio.Threading.Analyzers"
       Version="17.14.15"
     />
+    <GlobalPackageReference Include="PolySharp" Version="1.15.0" />
   </ItemGroup>
 </Project>

build/packages.lock.json

@@ -39,6 +39,12 @@
         "resolved": "17.14.15",
         "contentHash": "mXQPJsbuUD2ydq4/ffd8h8tSOFCXec+2xJOVNCvXjuMOq/+5EKHq3D2m2MC2+nUaXeFMSt66VS/J4HdKBixgcw=="
       },
+      "PolySharp": {
+        "type": "Direct",
+        "requested": "[1.15.0, )",
+        "resolved": "1.15.0",
+        "contentHash": "FbU0El+EEjdpuIX4iDbeS7ki1uzpJPx8vbqOzEtqnl1GZeAGJfq+jCbxeJL2y0EPnUNk8dRnnqR2xnYXg9Tf+g=="
+      },
       "SimpleExec": {
         "type": "Direct",
         "requested": "[13.0.0, )",

src/SharpCompress/Archives/ArchiveInformation.cs

@@ -10,13 +10,29 @@ namespace SharpCompress.Archives;
 /// <see cref="ArchiveFactory.GetArchiveInformationAsync(System.IO.Stream,System.Threading.CancellationToken)"/>
 /// to obtain an instance of this record.
 /// </remarks>
-/// <param name="Type">
-/// The type of archive detected, or <see langword="null"/> when the format is not a registered well-known type.
-/// </param>
-/// <param name="SupportsRandomAccess">
-/// <see langword="true"/> when this archive format supports random access via the <see cref="IArchive"/> API,
-/// meaning the full file listing can be retrieved without decompressing the entire archive.
-/// <see langword="false"/> when only the <see cref="SharpCompress.Readers.IReader"/> API is available,
-/// which reads entries sequentially and can only report per-entry progress.
-/// </param>
-public record ArchiveInformation(ArchiveType? Type, bool SupportsRandomAccess);
+public record ArchiveInformation
+{
+    /// <summary>
+    /// The type of archive detected, or <see langword="null"/> when the format is not a registered well-known type.
+    /// </summary>
+    public ArchiveType? Type { get; set; }
+
+    /// <summary>
+    /// <see langword="true"/> when this archive format supports random access via the <see cref="IArchive"/> API,
+    /// meaning the full file listing can be retrieved without decompressing the entire archive.
+    /// <see langword="false"/> when only the <see cref="SharpCompress.Readers.IReader"/> API is available,
+    /// which reads entries sequentially and can only report per-entry progress.
+    /// </summary>
+    public bool SupportsRandomAccess { get; set; }
+
+    /// <summary>
+    /// Creates a new archive information instance.
+    /// </summary>
+    /// <param name="type">The detected archive type.</param>
+    /// <param name="supportsRandomAccess">Whether the detected format supports random access.</param>
+    public ArchiveInformation(ArchiveType? type, bool supportsRandomAccess)
+    {
+        Type = type;
+        SupportsRandomAccess = supportsRandomAccess;
+    }
+}

src/SharpCompress/Common/ExtractionOptions.cs

@@ -7,7 +7,7 @@ namespace SharpCompress.Common;
 /// Options for configuring extraction behavior when extracting archive entries.
 /// </summary>
 /// <remarks>
-/// This class is immutable. Use the <c>with</c> expression to create modified copies:
+/// Configure extraction behavior with constructors, property setters, or the <c>with</c> expression:
 /// <code>
 /// var options = new ExtractionOptions { Overwrite = false };
 /// options = options with { PreserveFileTime = true };
@@ -19,35 +19,35 @@ public sealed record ExtractionOptions : IExtractionOptions
     /// Overwrite target if it exists.
     /// <para><b>Breaking change:</b> Default changed from false to true in version 0.40.0.</para>
     /// </summary>
-    public bool Overwrite { get; init; } = true;
+    public bool Overwrite { get; set; } = true;
 
     /// <summary>
     /// Extract with internal directory structure.
     /// <para><b>Breaking change:</b> Default changed from false to true in version 0.40.0.</para>
     /// </summary>
-    public bool ExtractFullPath { get; init; } = true;
+    public bool ExtractFullPath { get; set; } = true;
 
     /// <summary>
     /// Preserve file time.
     /// <para><b>Breaking change:</b> Default changed from false to true in version 0.40.0.</para>
     /// </summary>
-    public bool PreserveFileTime { get; init; } = true;
+    public bool PreserveFileTime { get; set; } = true;
 
     /// <summary>
     /// Preserve windows file attributes.
     /// </summary>
-    public bool PreserveAttributes { get; init; }
+    public bool PreserveAttributes { get; set; }
 
     /// <summary>
     /// Delegate for writing symbolic links to disk.
     /// The first parameter is the source path (where the symlink is created).
     /// The second parameter is the target path (what the symlink refers to).
     /// </summary>
     /// <remarks>
-    /// <b>Breaking change:</b> Changed from field to init-only property in version 0.40.0.
+    /// <b>Breaking change:</b> Changed from field to property in version 0.40.0.
     /// If no handler is provided, symbolic links are silently skipped during extraction.
     /// </remarks>
-    public Action<string, string>? SymbolicLinkHandler { get; init; }
+    public Action<string, string>? SymbolicLinkHandler { get; set; }
 
     /// <summary>
     /// Creates a new ExtractionOptions instance with default values.

src/SharpCompress/Common/Options/IEncodingOptions.cs

@@ -2,5 +2,5 @@ namespace SharpCompress.Common.Options;
 
 public interface IEncodingOptions
 {
-    IArchiveEncoding ArchiveEncoding { get; init; }
+    IArchiveEncoding ArchiveEncoding { get; set; }
 }

src/SharpCompress/Common/Options/IExtractionOptions.cs

@@ -11,29 +11,29 @@ public interface IExtractionOptions
     /// Overwrite target if it exists.
     /// <para><b>Breaking change:</b> Default changed from false to true in version 0.40.0.</para>
     /// </summary>
-    bool Overwrite { get; init; }
+    bool Overwrite { get; set; }
 
     /// <summary>
     /// Extract with internal directory structure.
     /// <para><b>Breaking change:</b> Default changed from false to true in version 0.40.0.</para>
     /// </summary>
-    bool ExtractFullPath { get; init; }
+    bool ExtractFullPath { get; set; }
 
     /// <summary>
     /// Preserve file time.
     /// <para><b>Breaking change:</b> Default changed from false to true in version 0.40.0.</para>
     /// </summary>
-    bool PreserveFileTime { get; init; }
+    bool PreserveFileTime { get; set; }
 
     /// <summary>
     /// Preserve windows file attributes.
     /// </summary>
-    bool PreserveAttributes { get; init; }
+    bool PreserveAttributes { get; set; }
 
     /// <summary>
     /// Delegate for writing symbolic links to disk.
     /// The first parameter is the source path (where the symlink is created).
     /// The second parameter is the target path (what the symlink refers to).
     /// </summary>
-    Action<string, string>? SymbolicLinkHandler { get; init; }
+    Action<string, string>? SymbolicLinkHandler { get; set; }
 }

src/SharpCompress/Common/Options/IProgressOptions.cs

@@ -4,5 +4,5 @@ namespace SharpCompress.Common.Options;
 
 public interface IProgressOptions
 {
-    IProgress<ProgressReport>? Progress { get; init; }
+    IProgress<ProgressReport>? Progress { get; set; }
 }

src/SharpCompress/Common/Options/IReaderOptions.cs

@@ -8,37 +8,37 @@ public interface IReaderOptions : IStreamOptions, IEncodingOptions, IProgressOpt
     /// <summary>
     /// Look for RarArchive (Check for self-extracting archives or cases where RarArchive isn't at the start of the file)
     /// </summary>
-    bool LookForHeader { get; init; }
+    bool LookForHeader { get; set; }
 
     /// <summary>
     /// Password for encrypted archives.
     /// </summary>
-    string? Password { get; init; }
+    string? Password { get; set; }
 
     /// <summary>
     /// Disable checking for incomplete archives.
     /// </summary>
-    bool DisableCheckIncomplete { get; init; }
+    bool DisableCheckIncomplete { get; set; }
 
     /// <summary>
     /// Buffer size for stream operations.
     /// </summary>
-    int BufferSize { get; init; }
+    int BufferSize { get; set; }
 
     /// <summary>
     /// Provide a hint for the extension of the archive being read, can speed up finding the correct decoder.
     /// </summary>
-    string? ExtensionHint { get; init; }
+    string? ExtensionHint { get; set; }
 
     /// <summary>
     /// Size of the rewindable buffer for non-seekable streams.
     /// </summary>
-    int? RewindableBufferSize { get; init; }
+    int? RewindableBufferSize { get; set; }
 
     /// <summary>
     /// Registry of compression providers.
     /// Defaults to <see cref="CompressionProviderRegistry.Default" /> but can be replaced with custom providers.
     /// Use this to provide alternative decompression implementations.
     /// </summary>
-    CompressionProviderRegistry Providers { get; init; }
+    CompressionProviderRegistry Providers { get; set; }
 }

src/SharpCompress/Common/Options/IStreamOptions.cs

@@ -2,5 +2,5 @@ namespace SharpCompress.Common.Options;
 
 public interface IStreamOptions
 {
-    bool LeaveStreamOpen { get; init; }
+    bool LeaveStreamOpen { get; set; }
 }

src/SharpCompress/Common/Options/IWriterOptions.cs

@@ -12,17 +12,17 @@ public interface IWriterOptions : IStreamOptions, IEncodingOptions, IProgressOpt
     /// <summary>
     /// The compression type to use for the archive.
     /// </summary>
-    CompressionType CompressionType { get; init; }
+    CompressionType CompressionType { get; set; }
 
     /// <summary>
     /// The compression level to be used when the compression type supports variable levels.
     /// </summary>
-    int CompressionLevel { get; init; }
+    int CompressionLevel { get; set; }
 
     /// <summary>
     /// Registry of compression providers.
     /// Defaults to <see cref="CompressionProviderRegistry.Default" /> but can be replaced with custom providers, such as
     /// System.IO.Compression for Deflate/GZip on modern .NET.
     /// </summary>
-    CompressionProviderRegistry Providers { get; init; }
+    CompressionProviderRegistry Providers { get; set; }
 }

src/SharpCompress/Providers/CompressionContext.cs

@@ -12,22 +12,22 @@ public sealed record CompressionContext
     /// <summary>
     /// The size of the input data, or -1 if unknown.
     /// </summary>
-    public long InputSize { get; init; } = -1;
+    public long InputSize { get; set; } = -1;
 
     /// <summary>
     /// The expected output size, or -1 if unknown.
     /// </summary>
-    public long OutputSize { get; init; } = -1;
+    public long OutputSize { get; set; } = -1;
 
     /// <summary>
     /// Properties bytes for the compression format (e.g., LZMA properties).
     /// </summary>
-    public byte[]? Properties { get; init; }
+    public byte[]? Properties { get; set; }
 
     /// <summary>
     /// Whether the underlying stream supports seeking.
     /// </summary>
-    public bool CanSeek { get; init; }
+    public bool CanSeek { get; set; }
 
     /// <summary>
     /// Additional format-specific options.
@@ -38,7 +38,7 @@ public sealed record CompressionContext
     /// Examples of valid FormatOptions values include compression properties (e.g., LZMA properties),
     /// format flags, or algorithm-specific configuration.
     /// </remarks>
-    public object? FormatOptions { get; init; }
+    public object? FormatOptions { get; set; }
 
     /// <summary>
     /// Creates a CompressionContext from a stream.
@@ -51,7 +51,7 @@ public static CompressionContext FromStream(Stream stream) =>
     /// <summary>
     /// Reader options for accessing archive metadata such as header encoding.
     /// </summary>
-    public IReaderOptions? ReaderOptions { get; init; }
+    public IReaderOptions? ReaderOptions { get; set; }
 
     /// <summary>
     /// Returns a new <see cref="CompressionContext"/> with the specified reader options.

src/SharpCompress/Readers/ReaderOptions.cs

@@ -10,7 +10,7 @@ namespace SharpCompress.Readers;
 /// Options for configuring reader behavior when opening archives.
 /// </summary>
 /// <remarks>
-/// This class is immutable. Use preset properties and fluent helpers for common configurations:
+/// Use preset properties, setters, and fluent helpers for common configurations:
 /// <code>
 /// var options = ReaderOptions.ForExternalStream
 ///     .WithPassword("secret")
@@ -53,43 +53,43 @@ public sealed record ReaderOptions : IReaderOptions
     /// </code>
     /// </para>
     /// </remarks>
-    public bool LeaveStreamOpen { get; init; } = false;
+    public bool LeaveStreamOpen { get; set; } = false;
 
     /// <summary>
     /// Encoding to use for archive entry names.
     /// </summary>
-    public IArchiveEncoding ArchiveEncoding { get; init; } = new ArchiveEncoding();
+    public IArchiveEncoding ArchiveEncoding { get; set; } = new ArchiveEncoding();
 
     /// <summary>
     /// Look for RarArchive (Check for self-extracting archives or cases where RarArchive isn't at the start of the file)
     /// </summary>
-    public bool LookForHeader { get; init; }
+    public bool LookForHeader { get; set; }
 
     /// <summary>
     /// Password for encrypted archives.
     /// </summary>
-    public string? Password { get; init; }
+    public string? Password { get; set; }
 
     /// <summary>
     /// Disable checking for incomplete archives.
     /// </summary>
-    public bool DisableCheckIncomplete { get; init; }
+    public bool DisableCheckIncomplete { get; set; }
 
     /// <summary>
     /// Buffer size for stream operations.
     /// </summary>
-    public int BufferSize { get; init; } = Constants.BufferSize;
+    public int BufferSize { get; set; } = Constants.BufferSize;
 
     /// <summary>
     /// Provide a hint for the extension of the archive being read, can speed up finding the correct decoder.  Should be without the leading period in the form like: tar.gz or zip
     /// </summary>
-    public string? ExtensionHint { get; init; }
+    public string? ExtensionHint { get; set; }
 
     /// <summary>
     /// An optional progress reporter for tracking extraction operations.
     /// When set, progress updates will be reported as entries are extracted.
     /// </summary>
-    public IProgress<ProgressReport>? Progress { get; init; }
+    public IProgress<ProgressReport>? Progress { get; set; }
 
     /// <summary>
     /// Size of the rewindable buffer for non-seekable streams.
@@ -133,14 +133,14 @@ public sealed record ReaderOptions : IReaderOptions
     /// using var reader = ReaderFactory.OpenReader(networkStream, options);
     /// </code>
     /// </example>
-    public int? RewindableBufferSize { get; init; }
+    public int? RewindableBufferSize { get; set; }
 
     /// <summary>
     /// Registry of compression providers.
     /// Defaults to <see cref="CompressionProviderRegistry.Default" /> but can be replaced with custom implementations, such as
     /// System.IO.Compression for Deflate/GZip on modern .NET.
     /// </summary>
-    public CompressionProviderRegistry Providers { get; init; } =
+    public CompressionProviderRegistry Providers { get; set; } =
         CompressionProviderRegistry.Default;
 
     /// <summary>