Adding tagged union serializer 🚀 (#1397)

src/common/mod.rs

@@ -0,0 +1 @@
+pub(crate) mod union;

src/common/union.rs

@@ -0,0 +1,43 @@
+use pyo3::prelude::*;
+use pyo3::{PyTraverseError, PyVisit};
+
+use crate::lookup_key::LookupKey;
+use crate::py_gc::PyGcTraverse;
+
+#[derive(Debug, Clone)]
+pub enum Discriminator {
+    /// use `LookupKey` to find the tag, same as we do to find values in typed_dict aliases
+    LookupKey(LookupKey),
+    /// call a function to find the tag to use
+    Function(PyObject),
+}
+
+impl Discriminator {
+    pub fn new(py: Python, raw: &Bound<'_, PyAny>) -> PyResult<Self> {
+        if raw.is_callable() {
+            return Ok(Self::Function(raw.to_object(py)));
+        }
+
+        let lookup_key = LookupKey::from_py(py, raw, None)?;
+        Ok(Self::LookupKey(lookup_key))
+    }
+
+    pub fn to_string_py(&self, py: Python) -> PyResult<String> {
+        match self {
+            Self::Function(f) => Ok(format!("{}()", f.getattr(py, "__name__")?)),
+            Self::LookupKey(lookup_key) => Ok(lookup_key.to_string()),
+        }
+    }
+}
+
+impl PyGcTraverse for Discriminator {
+    fn py_gc_traverse(&self, visit: &PyVisit<'_>) -> Result<(), PyTraverseError> {
+        match self {
+            Self::Function(obj) => visit.call(obj)?,
+            Self::LookupKey(_) => {}
+        }
+        Ok(())
+    }
+}
+
+pub(crate) const SMALL_UNION_THRESHOLD: usize = 4;

src/input/input_abstract.rs

@@ -239,7 +239,6 @@ pub trait ValidatedDict<'py> {
     where
         Self: 'a;
     fn get_item<'k>(&self, key: &'k LookupKey) -> ValResult<Option<(&'k LookupPath, Self::Item<'_>)>>;
-    fn as_py_dict(&self) -> Option<&Bound<'py, PyDict>>;
     // FIXME this is a bit of a leaky abstraction
     fn is_py_get_attr(&self) -> bool {
         false
@@ -282,9 +281,6 @@ impl<'py> ValidatedDict<'py> for Never {
     fn get_item<'k>(&self, _key: &'k LookupKey) -> ValResult<Option<(&'k LookupPath, Self::Item<'_>)>> {
         unreachable!()
     }
-    fn as_py_dict(&self) -> Option<&Bound<'py, PyDict>> {
-        unreachable!()
-    }
     fn iterate<'a, R>(
         &'a self,
         _consumer: impl ConsumeIterator<ValResult<(Self::Key<'a>, Self::Item<'a>)>, Output = R>,

src/input/input_json.rs

@@ -509,10 +509,6 @@ impl<'py, 'data> ValidatedDict<'py> for &'_ JsonObject<'data> {
         key.json_get(self)
     }
 
-    fn as_py_dict(&self) -> Option<&Bound<'py, PyDict>> {
-        None
-    }
-
     fn iterate<'a, R>(
         &'a self,
         consumer: impl ConsumeIterator<ValResult<(Self::Key<'a>, Self::Item<'a>)>, Output = R>,

src/input/input_python.rs

@@ -817,13 +817,6 @@ impl<'py> ValidatedDict<'py> for GenericPyMapping<'_, 'py> {
         matches!(self, Self::GetAttr(..))
     }
 
-    fn as_py_dict(&self) -> Option<&Bound<'py, PyDict>> {
-        match self {
-            Self::Dict(dict) => Some(dict),
-            _ => None,
-        }
-    }
-
     fn iterate<'a, R>(
         &'a self,
         consumer: impl ConsumeIterator<ValResult<(Self::Key<'a>, Self::Item<'a>)>, Output = R>,

src/input/input_string.rs

@@ -293,9 +293,6 @@ impl<'py> ValidatedDict<'py> for StringMappingDict<'py> {
     fn get_item<'k>(&self, key: &'k LookupKey) -> ValResult<Option<(&'k LookupPath, Self::Item<'_>)>> {
         key.py_get_string_mapping_item(&self.0)
     }
-    fn as_py_dict(&self) -> Option<&Bound<'py, PyDict>> {
-        None
-    }
     fn iterate<'a, R>(
         &'a self,
         consumer: impl super::ConsumeIterator<ValResult<(Self::Key<'a>, Self::Item<'a>)>, Output = R>,

src/lib.rs

@@ -16,6 +16,7 @@ mod py_gc;
 
 mod argument_markers;
 mod build_tools;
+mod common;
 mod definitions;
 mod errors;
 mod input;

src/serializers/shared.rs

@@ -88,7 +88,6 @@ combined_serializer! {
     // `find_only` is for type_serializers which are built directly via the `type` key and `find_serializer`
     // but aren't actually used for serialization, e.g. their `build` method must return another serializer
     find_only: {
-        super::type_serializers::union::TaggedUnionBuilder;
         super::type_serializers::other::ChainBuilder;
         super::type_serializers::other::CustomErrorBuilder;
         super::type_serializers::other::CallBuilder;
@@ -138,6 +137,7 @@ combined_serializer! {
         Json: super::type_serializers::json::JsonSerializer;
         JsonOrPython: super::type_serializers::json_or_python::JsonOrPythonSerializer;
         Union: super::type_serializers::union::UnionSerializer;
+        TaggedUnion: super::type_serializers::union::TaggedUnionSerializer;
         Literal: super::type_serializers::literal::LiteralSerializer;
         Enum: super::type_serializers::enum_::EnumSerializer;
         Recursive: super::type_serializers::definitions::DefinitionRefSerializer;
@@ -247,6 +247,7 @@ impl PyGcTraverse for CombinedSerializer {
             CombinedSerializer::Json(inner) => inner.py_gc_traverse(visit),
             CombinedSerializer::JsonOrPython(inner) => inner.py_gc_traverse(visit),
             CombinedSerializer::Union(inner) => inner.py_gc_traverse(visit),
+            CombinedSerializer::TaggedUnion(inner) => inner.py_gc_traverse(visit),
             CombinedSerializer::Literal(inner) => inner.py_gc_traverse(visit),
             CombinedSerializer::Enum(inner) => inner.py_gc_traverse(visit),
             CombinedSerializer::Recursive(inner) => inner.py_gc_traverse(visit),