add serde serialization support

Cargo.toml

@@ -36,17 +36,22 @@ harness = false
 # implement its `Allocator` trait.
 allocator-api2 = { version = "0.2.8", default-features = false, optional = true }
 
+# This dependency is here to allow integration with Serde, if the `serde` feature is enabled
+serde = { version = "1.0.171", optional = true }
+
 [dev-dependencies]
 quickcheck = "1.0.3"
 criterion = "0.3.6"
 rand = "0.8.5"
+serde_json = "1.0.115"
 
 [features]
 default = []
 collections = []
 boxed = []
 allocator_api = []
 std = []
+serde = ["dep:serde"]
 
 # [profile.bench]
 # debug = true

README.md

@@ -102,7 +102,32 @@ arenas.
 }
 ```
 
-Eventually [all `std` collection types will be parameterized by an
+#### Serde
+
+Adding the `serde` feature flag will enable transparent serialization for Vec.
+
+```toml
+[dependencies]
+bumpalo = { version = "3.9", features = ["collections", "serde"] }
+```
+
+```rust,ignore
+use bumpalo::{Bump, collections::Vec};
+
+// Create a new bump arena.
+let bump = Bump::new();
+
+// Create a `Box`
+let vec = Vec::new_in( &bump);
+vec.push(1);
+vec.push(2);
+
+// Serialize with serde_json
+assert_eq!(serde_json::to_string(&vec).unwrap(), "[1, 2]");
+```
+
+Eventually
+[all `std` collection types will be parameterized by an
 allocator](https://github.com/rust-lang/rust/issues/42774) and we can remove
 this `collections` module and use the `std` versions.
 
@@ -153,6 +178,29 @@ in its space itself.
 }
 ```
 
+#### Serde
+
+Adding the `serde` feature flag will enable transparent serialization of boxed
+values.
+
+```toml
+[dependencies]
+bumpalo = { version = "3.9", features = ["boxed", "serde"] }
+```
+
+```rust,ignore
+use bumpalo::{Bump, boxed::Box};
+
+// Create a new bump arena.
+let bump = Bump::new();
+
+// Create a `Box`
+let box = Box::new_in("hello", &bump);
+
+// Serialize with serde_json
+assert_eq!(serde_json::to_string(&box).unwrap(), "\"hello\"");
+```
+
 ### `#![no_std]` Support
 
 Bumpalo is a `no_std` crate by default. It depends only on the `alloc` and `core` crates.

src/boxed.rs

@@ -681,3 +681,16 @@ impl<'a, T, const N: usize> TryFrom<Box<'a, [T]>> for Box<'a, [T; N]> {
         }
     }
 }
+
+#[cfg(feature = "serde")]
+use serde::{Serialize, Serializer};
+
+#[cfg(feature = "serde")]
+impl<'a, T> Serialize for Box<'a, T>
+where
+    T: Serialize,
+{
+    fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
+        (**self).serialize(serializer)
+    }
+}

src/collections/vec.rs

@@ -2760,3 +2760,23 @@ impl<'bump> io::Write for Vec<'bump, u8> {
         Ok(())
     }
 }
+
+#[cfg(feature = "serde")]
+use serde::{ser::SerializeSeq, Serialize, Serializer};
+
+#[cfg(feature = "serde")]
+impl<'a, T> Serialize for Vec<'a, T>
+where
+    T: Serialize,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut seq = serializer.serialize_seq(Some(self.len))?;
+        for e in self.iter() {
+            seq.serialize_element(e)?;
+        }
+        seq.end()
+    }
+}

tests/all/boxed.rs

@@ -12,3 +12,13 @@ fn into_raw_aliasing() {
     let mut_ref = unsafe { &mut *raw };
     dbg!(mut_ref);
 }
+
+#[cfg(feature = "serde")]
+#[test]
+fn test_box_serializes() {
+    let bump = Bump::new();
+    let boxed = Box::new_in(1, &bump);
+    assert_eq!(serde_json::to_string(&boxed).unwrap(), "1");
+    let boxedStr = Box::new_in("a", &bump);
+    assert_eq!(serde_json::to_string(&boxedStr).unwrap(), "\"a\"");
+}

tests/all/vec.rs

@@ -167,3 +167,16 @@ fn test_vec_write() {
 
     assert_eq!(v, &[1, 2, 3]);
 }
+
+#[cfg(feature = "serde")]
+#[test]
+fn test_vec_serializes() {
+    let bump = Bump::new();
+    let mut vec = Vec::new_in(&bump);
+    vec.push("hello");
+    vec.push("world");
+    assert_eq!(
+        serde_json::to_string(&vec).unwrap(),
+        "[\"hello\",\"world\"]"
+    );
+}