feat: expose a visitor to deserialize a pyobject

CHANGELOG.md

@@ -1,3 +1,9 @@
+## Unreleased
+
+ - Add `pyobject` module for serialize and deserialize `PyObject`
+ - Add `PyObjectVisitor` that can be used to implement deserialize
+ - Add feature `serde_with`
+
 ## 0.21.1 - 2024-04-02
 
 - Fix compile error when using PyO3 `abi3` feature targeting a minimum version below 3.10

Cargo.toml

@@ -10,10 +10,15 @@ homepage = "https://github.com/davidhewitt/pythonize"
 repository = "https://github.com/davidhewitt/pythonize"
 documentation = "https://docs.rs/crate/pythonize/"
 
+[features]
+default = ["serde_with"]
+serde_with = ["serde-transcode"]
 
 [dependencies]
 serde = { version = "1.0", default-features = false, features = ["std"] }
 pyo3 = { version = "0.21.0", default-features = false }
+serde-transcode = { version = "1.0", default-features = false, optional = true }
+
 
 [dev-dependencies]
 serde = { version = "1.0", default-features = false, features = ["derive"] }

src/lib.rs

@@ -39,6 +39,7 @@
 mod de;
 mod error;
 mod ser;
+mod visitor;
 
 #[allow(deprecated)]
 pub use crate::de::depythonize;
@@ -48,3 +49,41 @@ pub use crate::ser::{
     pythonize, pythonize_custom, PythonizeDefault, PythonizeDictType, PythonizeListType,
     PythonizeTypes, Pythonizer,
 };
+pub use crate::visitor::PyObjectVisitor;
+
+#[cfg(feature = "serde_with")]
+/// This module provides a Serde `Serialize` and `Deserialize` implementation for `PyObject`.
+///
+/// ```rust
+/// use pyo3::PyObject;
+/// use serde::{Serialize, Deserialize};
+///
+/// #[derive(Serialize, Deserialize)]
+/// struct Foo {
+///   #[serde(with = "pythonize::pyobject")]
+///   #[serde(flatten)]
+///   inner: PyObject,
+/// }
+/// ```
+pub mod pyobject {
+    use pyo3::{PyObject, Python};
+    use serde::Serializer;
+
+    pub fn serialize<S>(obj: &PyObject, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        Python::with_gil(|py| {
+            let mut deserializer =
+                crate::Depythonizer::from_object_bound(obj.clone().into_bound(py));
+            serde_transcode::transcode(&mut deserializer, serializer)
+        })
+    }
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<PyObject, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        Python::with_gil(|py| deserializer.deserialize_any(crate::PyObjectVisitor::new(py)))
+    }
+}

src/visitor.rs

@@ -0,0 +1,183 @@
+use pyo3::{
+    types::{PyDict, PyDictMethods, PyList, PyListMethods},
+    PyObject, Python, ToPyObject,
+};
+use serde::{
+    de::{MapAccess, SeqAccess, VariantAccess, Visitor},
+    Deserialize,
+};
+
+pub struct PyObjectVisitor<'py> {
+    py: Python<'py>,
+}
+
+impl<'py> PyObjectVisitor<'py> {
+    pub fn new(py: Python) -> PyObjectVisitor<'_> {
+        PyObjectVisitor { py }
+    }
+}
+
+struct Wrapper {
+    inner: PyObject,
+}
+
+impl<'de> Deserialize<'de> for Wrapper {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        Python::with_gil(|py| {
+            deserializer
+                .deserialize_any(PyObjectVisitor { py })
+                .map(|inner| Wrapper { inner })
+        })
+    }
+}
+
+impl<'de, 'py> Visitor<'de> for PyObjectVisitor<'py> {
+    type Value = PyObject;
+
+    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+        formatter.write_str("any PyObject")
+    }
+
+    fn visit_bool<E>(self, value: bool) -> Result<Self::Value, E> {
+        Ok(value.to_object(self.py))
+    }
+
+    fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E> {
+        Ok(value.to_object(self.py))
+    }
+
+    fn visit_i128<E>(self, value: i128) -> Result<Self::Value, E> {
+        Ok(value.to_object(self.py))
+    }
+
+    fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E> {
+        Ok(value.to_object(self.py))
+    }
+
+    fn visit_u128<E>(self, value: u128) -> Result<Self::Value, E> {
+        Ok(value.to_object(self.py))
+    }
+
+    fn visit_f64<E>(self, value: f64) -> Result<Self::Value, E> {
+        Ok(value.to_object(self.py))
+    }
+
+    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E> {
+        Ok(value.to_object(self.py))
+    }
+
+    fn visit_string<E>(self, value: String) -> Result<Self::Value, E> {
+        Ok(value.to_object(self.py))
+    }
+
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E> {
+        Ok(v.to_object(self.py))
+    }
+
+    fn visit_none<E>(self) -> Result<Self::Value, E> {
+        Ok(self.py.None())
+    }
+
+    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let wrapper: Wrapper = Deserialize::deserialize(deserializer)?;
+        Ok(wrapper.inner)
+    }
+
+    fn visit_unit<E: serde::de::Error>(self) -> Result<Self::Value, E> {
+        self.visit_none()
+    }
+
+    fn visit_seq<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
+    where
+        V: SeqAccess<'de>,
+    {
+        let list = PyList::empty_bound(self.py);
+
+        while let Some(wrapper) = visitor.next_element::<Wrapper>()? {
+            list.append(wrapper.inner).unwrap();
+        }
+
+        Ok(list.to_object(self.py))
+    }
+
+    fn visit_map<V>(self, mut visitor: V) -> Result<Self::Value, V::Error>
+    where
+        V: MapAccess<'de>,
+    {
+        let dict = PyDict::new_bound(self.py);
+
+        while let Some((key, value)) = visitor.next_entry::<Wrapper, Wrapper>()? {
+            dict.set_item(key.inner, value.inner).unwrap();
+        }
+
+        Ok(dict.to_object(self.py))
+    }
+
+    fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error>
+    where
+        A: serde::de::EnumAccess<'de>,
+    {
+        let dict = PyDict::new_bound(self.py);
+        let (value, variant): (Wrapper, _) = data.variant()?;
+        let variant: Wrapper = variant.newtype_variant()?;
+        dict.set_item(variant.inner, value.inner).unwrap();
+
+        Ok(dict.to_object(self.py))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use pyo3::{
+        types::{PyAnyMethods, PyStringMethods},
+        PyObject, Python,
+    };
+    use serde::{Deserialize, Serialize};
+    use serde_json::json;
+
+    #[derive(Serialize, Deserialize)]
+    struct Foo {
+        #[serde(with = "crate::pyobject")]
+        #[serde(flatten)]
+        inner: PyObject,
+    }
+
+    #[test]
+    fn simple_test() {
+        let value = json!({
+            "code": 200,
+            "success": true,
+            "payload": {
+                "features": [
+                    "serde",
+                    "json"
+                ],
+                "homepage": null
+            }
+        });
+
+        Python::with_gil(|py| {
+            let foo = Foo {
+                inner: crate::pythonize(py, &value).unwrap(),
+            };
+            let serialized = serde_json::to_string(&foo).unwrap();
+            let deserialized: Foo = serde_json::from_str(&serialized).unwrap();
+            assert_eq!(
+                deserialized
+                    .inner
+                    .bind(py)
+                    .repr()
+                    .unwrap()
+                    .to_str()
+                    .unwrap(),
+                foo.inner.bind(py).repr().unwrap().to_str().unwrap()
+            );
+        });
+    }
+}