Expose serialization api (pythonnet#2336)

BadSingleton · filmor · web-flow · commit 32051cb3c7c2 · 2024-05-10T10:35:55.000-07:00
* Expose an API for users to specify their own formatter

Adds post-serialization and pre-deserialization hooks for additional
customization.

* Add API for capsuling data when serializing

* Add NoopFormatter and fall back to it if BinaryFormatter is not available

---------

Co-authored-by: Benedikt Reinartz &lt;filmor@gmail.com&gt;
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -15,6 +15,9 @@ This document follows the conventions laid out in [Keep a CHANGELOG][].
      to compare with primitive .NET types like `long`.
 
 ### Changed
+-   Added a `FormatterFactory` member in RuntimeData to create formatters with parameters. For compatibility, the `FormatterType` member is still present and has precedence when defining both `FormatterFactory` and `FormatterType`
+-   Added a post-serialization and a pre-deserialization step callbacks to extend (de)serialization process
+-   Added an API to stash serialized data on Python capsules
 
 ### Fixed
 
diff --git a/src/runtime/StateSerialization/NoopFormatter.cs b/src/runtime/StateSerialization/NoopFormatter.cs
@@ -0,0 +1,14 @@
+using System;
+using System.IO;
+using System.Runtime.Serialization;
+
+namespace Python.Runtime;
+
+public class NoopFormatter : IFormatter {
+    public object Deserialize(Stream s) => throw new NotImplementedException();
+    public void Serialize(Stream s, object o) {}
+
+    public SerializationBinder? Binder { get; set; }
+    public StreamingContext Context { get; set; }
+    public ISurrogateSelector? SurrogateSelector { get; set; }
+}
diff --git a/src/runtime/StateSerialization/RuntimeData.cs b/src/runtime/StateSerialization/RuntimeData.cs
@@ -1,7 +1,5 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
-using System.Collections.ObjectModel;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
@@ -17,7 +15,34 @@ namespace Python.Runtime
 {
     public static class RuntimeData
     {
-        private static Type? _formatterType;
+
+        public readonly static Func<IFormatter> DefaultFormatterFactory = () =>
+        {
+            try
+            {
+                return new BinaryFormatter();
+            }
+            catch
+            {
+                return new NoopFormatter();
+            }
+        };
+
+        private static Func<IFormatter> _formatterFactory { get; set; } = DefaultFormatterFactory;
+
+        public static Func<IFormatter> FormatterFactory
+        {
+            get => _formatterFactory;
+            set
+            {
+                if (value == null)
+                    throw new ArgumentNullException(nameof(value));
+
+                _formatterFactory = value;
+            }
+        }
+
+        private static Type? _formatterType = null;
         public static Type? FormatterType
         {
             get => _formatterType;
@@ -31,6 +56,14 @@ public static Type? FormatterType
             }
         }
 
+        /// <summary>
+        /// Callback called as a last step in the serialization process
+        /// </summary>
+        public static Action? PostStashHook { get; set; } = null;
+        /// <summary>
+        /// Callback called as the first step in the deserialization process
+        /// </summary>
+        public static Action? PreRestoreHook { get; set; } = null;
         public static ICLRObjectStorer? WrappersStorer { get; set; }
 
         /// <summary>
@@ -74,6 +107,7 @@ internal static void Stash()
             using NewReference capsule = PyCapsule_New(mem, IntPtr.Zero, IntPtr.Zero);
             int res = PySys_SetObject("clr_data", capsule.BorrowOrThrow());
             PythonException.ThrowIfIsNotZero(res);
+            PostStashHook?.Invoke();
         }
 
         internal static void RestoreRuntimeData()
@@ -90,6 +124,7 @@ internal static void RestoreRuntimeData()
 
         private static void RestoreRuntimeDataImpl()
         {
+            PreRestoreHook?.Invoke();
             BorrowedReference capsule = PySys_GetObject("clr_data");
             if (capsule.IsNull)
             {
@@ -250,11 +285,102 @@ private static void RestoreRuntimeDataObjects(SharedObjectsState storage)
             }
         }
 
+        static readonly string serialization_key_namepsace = "pythonnet_serialization_";
+        /// <summary>
+        /// Removes the serialization capsule from the `sys` module object.
+        /// </summary>
+        /// <remarks>
+        /// The serialization data must have been set with <code>StashSerializationData</code>
+        /// </remarks>
+        /// <param name="key">The name given to the capsule on the `sys` module object</param>
+        public static void FreeSerializationData(string key)
+        {
+            key = serialization_key_namepsace + key;
+            BorrowedReference oldCapsule = PySys_GetObject(key);
+            if (!oldCapsule.IsNull)
+            {
+                IntPtr oldData = PyCapsule_GetPointer(oldCapsule, IntPtr.Zero);
+                Marshal.FreeHGlobal(oldData);
+                PyCapsule_SetPointer(oldCapsule, IntPtr.Zero);
+                PySys_SetObject(key, null);
+            }
+        }
+
+        /// <summary>
+        /// Stores the data in the <paramref name="stream"/> argument in a Python capsule and stores
+        /// the capsule on the `sys` module object with the name <paramref name="key"/>.
+        /// </summary>
+        /// <remarks>
+        /// No checks on pre-existing names on the `sys` module object are made.
+        /// </remarks>
+        /// <param name="key">The name given to the capsule on the `sys` module object</param>
+        /// <param name="stream">A MemoryStream that contains the data to be placed in the capsule</param>
+        public static void StashSerializationData(string key, MemoryStream stream)
+        {
+            if (stream.TryGetBuffer(out var data))
+            {
+                IntPtr mem = Marshal.AllocHGlobal(IntPtr.Size + data.Count);
+
+                // store the length of the buffer first
+                Marshal.WriteIntPtr(mem, (IntPtr)data.Count);
+                Marshal.Copy(data.Array, data.Offset, mem + IntPtr.Size, data.Count);
+
+                try
+                {
+                    using NewReference capsule = PyCapsule_New(mem, IntPtr.Zero, IntPtr.Zero);
+                    int res = PySys_SetObject(key, capsule.BorrowOrThrow());
+                    PythonException.ThrowIfIsNotZero(res);
+                }
+                catch
+                {
+                    Marshal.FreeHGlobal(mem);
+                }
+            }
+            else
+            {
+                throw new NotImplementedException($"{nameof(stream)} must be exposable");
+            }
+
+        }
+
+        static byte[] emptyBuffer = new byte[0];
+        /// <summary>
+        /// Retreives the previously stored data on a Python capsule.
+        /// Throws if the object corresponding to the <paramref name="key"/> parameter
+        /// on the `sys` module object is not a capsule.
+        /// </summary>
+        /// <param name="key">The name given to the capsule on the `sys` module object</param>
+        /// <returns>A MemoryStream containing the previously saved serialization data.
+        /// The stream is empty if no name matches the key.  </returns>
+        public static MemoryStream GetSerializationData(string key)
+        {
+            BorrowedReference capsule = PySys_GetObject(key);
+            if (capsule.IsNull)
+            {
+                // nothing to do.
+                return new MemoryStream(emptyBuffer, writable:false);
+            }
+            var ptr = PyCapsule_GetPointer(capsule, IntPtr.Zero);
+            if (ptr == IntPtr.Zero)
+            {
+                // The PyCapsule API returns NULL on error; NULL cannot be stored
+                // as a capsule's value
+                PythonException.ThrowIfIsNull(null);
+            }
+            var len = (int)Marshal.ReadIntPtr(ptr);
+            byte[] buffer = new byte[len];
+            Marshal.Copy(ptr+IntPtr.Size, buffer, 0, len);
+            return new MemoryStream(buffer, writable:false);
+        }
+
         internal static IFormatter CreateFormatter()
         {
-            return FormatterType != null ?
-                (IFormatter)Activator.CreateInstance(FormatterType)
-                : new BinaryFormatter();
+
+            if (FormatterType != null)
+            {
+                return (IFormatter)Activator.CreateInstance(FormatterType);
+            }
+            return FormatterFactory();
         }
     }
 }
diff --git a/tests/domain_tests/TestRunner.cs b/tests/domain_tests/TestRunner.cs
@@ -1132,6 +1132,66 @@ import System
     
                     ",
             },
+            new TestCase
+            {
+                Name = "test_serialize_unserializable_object",
+                DotNetBefore = @"    
+                namespace TestNamespace
+                {
+                    public class NotSerializableTextWriter :  System.IO.TextWriter
+                    {
+                        override public System.Text.Encoding Encoding { get { return System.Text.Encoding.ASCII;} }
+                    }
+                    [System.Serializable]
+                    public static class SerializableWriter
+                    {
+                        private static System.IO.TextWriter _writer = null;
+                        public static System.IO.TextWriter Writer {get { return _writer; }}
+                        public static void CreateInternalWriter()
+                        {
+                            _writer = System.IO.TextWriter.Synchronized(new NotSerializableTextWriter());
+                        }
+                    }
+                }
+",
+                DotNetAfter = @"
+                namespace TestNamespace
+                {
+                    public class NotSerializableTextWriter :  System.IO.TextWriter
+                    {
+                        override public System.Text.Encoding Encoding { get { return System.Text.Encoding.ASCII;} }
+                    }
+                    [System.Serializable]
+                    public static class SerializableWriter
+                    {
+                        private static System.IO.TextWriter _writer = null;
+                        public static System.IO.TextWriter Writer {get { return _writer; }}
+                        public static void CreateInternalWriter()
+                        {
+                            _writer = System.IO.TextWriter.Synchronized(new NotSerializableTextWriter());
+                        }
+                    }
+                }
+                ",
+                PythonCode = @"
+import sys
+
+def before_reload():
+    import clr
+    import System
+    clr.AddReference('DomainTests')
+    import TestNamespace
+    TestNamespace.SerializableWriter.CreateInternalWriter();
+    sys.__obj = TestNamespace.SerializableWriter.Writer
+    sys.__obj.WriteLine('test')
+
+def after_reload():
+    import clr
+    import System
+    sys.__obj.WriteLine('test')
+    
+                    ",
+            }
         };
 
         /// <summary>
@@ -1142,7 +1202,59 @@ import System
         const string CaseRunnerTemplate = @"
 using System;
 using System.IO;
+using System.Runtime.Serialization;
+using System.Runtime.Serialization.Formatters.Binary;
 using Python.Runtime;
+
+namespace Serialization
+{{
+    // Classes in this namespace is mostly useful for test_serialize_unserializable_object
+    class NotSerializableSerializer : ISerializationSurrogate
+    {{
+        public NotSerializableSerializer()
+        {{
+        }}
+        public void GetObjectData(object obj, SerializationInfo info, StreamingContext context)
+        {{
+            info.AddValue(""notSerialized_tp"", obj.GetType());
+        }}
+        public object SetObjectData(object obj, SerializationInfo info, StreamingContext context, ISurrogateSelector selector)
+        {{
+            if (info == null)
+            {{
+                return null;
+            }}
+            Type typeObj = info.GetValue(""notSerialized_tp"", typeof(Type)) as Type;
+            if (typeObj == null)
+            {{
+                return null;
+            }}
+            
+            obj = Activator.CreateInstance(typeObj);
+            return obj;
+        }}
+    }}
+    class NonSerializableSelector : SurrogateSelector
+    {{
+        public override ISerializationSurrogate GetSurrogate(Type type, StreamingContext context, out ISurrogateSelector selector)
+        {{
+            if (type == null)
+            {{
+                throw new ArgumentNullException();
+            }}
+            selector = (ISurrogateSelector)this;
+            if (type.IsSerializable)
+            {{
+                return null; // use whichever default
+            }}
+            else
+            {{
+                return (ISerializationSurrogate)(new NotSerializableSerializer());
+            }}
+        }}
+    }}
+}}
+
 namespace CaseRunner
 {{
     class CaseRunner
@@ -1151,6 +1263,11 @@ public static int Main()
         {{
             try
             {{
+                RuntimeData.FormatterFactory = () => 
+                {{ 
+                    return new BinaryFormatter(){{SurrogateSelector = new Serialization.NonSerializableSelector()}};
+                }};
+
                 PythonEngine.Initialize();
                 using (Py.GIL())
                 {{
diff --git a/tests/domain_tests/test_domain_reload.py b/tests/domain_tests/test_domain_reload.py
@@ -88,3 +88,6 @@ def test_nested_type():
 
 def test_import_after_reload():
     _run_test("import_after_reload")
+
+def test_import_after_reload():
+    _run_test("test_serialize_unserializable_object")
