New helper for sticking Serde-encodable data into arrow

crates/re_log_types/Cargo.toml

@@ -34,6 +34,7 @@ image = ["dep:ecolor", "dep:image"]
 
 ## Enable (de)serialization using serde.
 serde = [
+  "dep:rmp-serde",
   "dep:serde",
   "dep:serde_bytes",
   "half/serde",
@@ -89,13 +90,10 @@ image = { workspace = true, optional = true, default-features = false, features
 ] }
 macaw = { workspace = true, optional = true }
 rand = { version = "0.8", optional = true }
+rmp-serde = { version = "1.1", optional = true }
 serde = { version = "1", optional = true, features = ["derive", "rc"] }
 serde_bytes = { version = "0.11", optional = true }
 
 # Native dependencies:
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 puffin.workspace = true
-
-
-[dev-dependencies]
-rmp-serde = "1.1"

crates/re_log_types/src/lib.rs

@@ -23,6 +23,9 @@ pub mod time_point;
 mod time_range;
 mod time_real;
 
+#[cfg(feature = "serde")]
+pub mod serde_field;
+
 pub mod external {
     pub use arrow2;
     pub use arrow2_convert;

crates/re_log_types/src/serde_field.rs

@@ -0,0 +1,126 @@
+use arrow2::{
+    array::{BinaryArray, MutableBinaryArray, TryPush},
+    datatypes::DataType,
+};
+use arrow2_convert::{deserialize::ArrowDeserialize, field::ArrowField, serialize::ArrowSerialize};
+
+/// Helper for storing arbitrary serde-compatible types in an arrow2 [`BinaryArray`] field
+///
+/// Use as:
+/// ```
+/// use re_log_types::serde_field::SerdeField;
+/// use arrow2_convert::{ArrowDeserialize, ArrowField, ArrowSerialize, field::ArrowField};
+/// use arrow2::datatypes::{DataType, Field};
+///
+/// #[derive(Clone, Debug, PartialEq, serde::Deserialize, serde::Serialize)]
+/// struct SomeStruct {
+///     foo: String,
+///     bar: u32,
+/// }
+///
+/// #[derive(Clone, Debug, PartialEq, ArrowField, ArrowSerialize, ArrowDeserialize)]
+/// struct SomeArrowStruct {
+///     #[arrow_field(type = "SerdeField<SomeStruct>")]
+///     field: SomeStruct,
+/// }
+///
+/// assert_eq!(
+///     SomeArrowStruct::data_type(),
+///     DataType::Struct(vec![
+///         Field::new("field", DataType::Binary, false),
+///     ])
+/// );
+/// ```
+pub struct SerdeField<T>(std::marker::PhantomData<T>);
+
+impl<T> ArrowField for SerdeField<T>
+where
+    T: serde::ser::Serialize + serde::de::DeserializeOwned,
+{
+    type Type = T;
+
+    #[inline]
+    fn data_type() -> DataType {
+        arrow2::datatypes::DataType::Binary
+    }
+}
+
+impl<T> ArrowSerialize for SerdeField<T>
+where
+    T: serde::ser::Serialize + serde::de::DeserializeOwned,
+{
+    type MutableArrayType = MutableBinaryArray<i32>;
+    #[inline]
+    fn new_array() -> Self::MutableArrayType {
+        MutableBinaryArray::new()
+    }
+
+    fn arrow_serialize(
+        v: &<Self as ArrowField>::Type,
+        array: &mut Self::MutableArrayType,
+    ) -> arrow2::error::Result<()> {
+        let mut buf = Vec::new();
+        rmp_serde::encode::write_named(&mut buf, v).map_err(|_err| {
+            // TODO(jleibs): Could not get re_error::format() to work here
+            arrow2::error::Error::ExternalFormat("Could not encode as rmp".to_owned())
+        })?;
+        array.try_push(Some(buf))
+    }
+}
+
+impl<T> ArrowDeserialize for SerdeField<T>
+where
+    T: serde::ser::Serialize + serde::de::DeserializeOwned,
+{
+    type ArrayType = BinaryArray<i32>;
+
+    #[inline]
+    fn arrow_deserialize(v: <&Self::ArrayType as IntoIterator>::Item) -> Option<T> {
+        v.and_then(|v| rmp_serde::from_slice::<T>(v).ok())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::SerdeField;
+    use arrow2_convert::{ArrowDeserialize, ArrowField, ArrowSerialize};
+
+    #[derive(Clone, Debug, PartialEq, serde::Deserialize, serde::Serialize)]
+    struct SomeStruct {
+        foo: String,
+        bar: u32,
+    }
+
+    #[derive(Clone, Debug, PartialEq, ArrowField, ArrowSerialize, ArrowDeserialize)]
+    struct SomeArrowStruct {
+        #[arrow_field(type = "SerdeField<SomeStruct>")]
+        field: SomeStruct,
+    }
+
+    impl From<SomeStruct> for SomeArrowStruct {
+        fn from(s: SomeStruct) -> Self {
+            Self { field: s }
+        }
+    }
+
+    #[test]
+    fn round_trip_serdefield() {
+        use arrow2_convert::{deserialize::TryIntoCollection, serialize::TryIntoArrow};
+
+        let data: [SomeArrowStruct; 2] = [
+            SomeStruct {
+                foo: "hello".into(),
+                bar: 42,
+            }
+            .into(),
+            SomeStruct {
+                foo: "world".into(),
+                bar: 1983,
+            }
+            .into(),
+        ];
+        let array: Box<dyn arrow2::array::Array> = data.try_into_arrow().unwrap();
+        let ret: Vec<SomeArrowStruct> = array.try_into_collection().unwrap();
+        assert_eq!(&data, ret.as_slice());
+    }
+}