Fix deserialisation of Option<_> fields

Workaround for <serde-rs/serde#723>.
tesaguri · Feb 25, 2024 · 3e83761 · 3e83761
1 parent a208ee5
commit 3e83761
Show file tree

Hide file tree

Showing 11 changed files with 168 additions and 19 deletions.
diff --git a/crates/kitsune-type/src/ap/actor.rs b/crates/kitsune-type/src/ap/actor.rs
@@ -32,40 +32,48 @@ pub struct Actor {
     #[serde(deserialize_with = "jsonld::serde::FirstOk::deserialize")]
     pub r#type: ActorType,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub name: Option<String>,
     #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
     pub preferred_username: String,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub subject: Option<String>,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub icon: Option<MediaAttachment>,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub image: Option<MediaAttachment>,
     #[serde(default)]
     #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
     pub manually_approves_followers: bool,
     #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
     pub public_key: PublicKey,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub endpoints: Option<Endpoints>,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::FirstId::deserialize")]
+    #[serde(
+        deserialize_with = "jsonld::serde::Optional::<jsonld::serde::FirstId<_>>::deserialize"
+    )]
     pub featured: Option<String>,
     #[serde(deserialize_with = "jsonld::serde::FirstId::deserialize")]
     pub inbox: String,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::FirstId::deserialize")]
+    #[serde(
+        deserialize_with = "jsonld::serde::Optional::<jsonld::serde::FirstId<_>>::deserialize"
+    )]
     pub outbox: Option<String>,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::FirstId::deserialize")]
+    #[serde(
+        deserialize_with = "jsonld::serde::Optional::<jsonld::serde::FirstId<_>>::deserialize"
+    )]
     pub followers: Option<String>,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::FirstId::deserialize")]
+    #[serde(
+        deserialize_with = "jsonld::serde::Optional::<jsonld::serde::FirstId<_>>::deserialize"
+    )]
     pub following: Option<String>,
     #[serde(default = "Timestamp::now_utc")]
     pub published: Timestamp,
@@ -81,7 +89,9 @@ impl RdfNode for Actor {
 #[serde(rename_all = "camelCase")]
 pub struct Endpoints {
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::FirstId::deserialize")]
+    #[serde(
+        deserialize_with = "jsonld::serde::Optional::<jsonld::serde::FirstId<_>>::deserialize"
+    )]
     pub shared_inbox: Option<String>,
 }
 

diff --git a/crates/kitsune-type/src/ap/mod.rs b/crates/kitsune-type/src/ap/mod.rs
@@ -164,13 +164,15 @@ pub struct Object {
     #[serde(deserialize_with = "jsonld::serde::FirstId::deserialize")]
     pub attributed_to: String,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::FirstId::deserialize")]
+    #[serde(
+        deserialize_with = "jsonld::serde::Optional::<jsonld::serde::FirstId<_>>::deserialize"
+    )]
     pub in_reply_to: Option<String>,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub name: Option<String>,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub summary: Option<String>,
     #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
     pub content: String,
@@ -215,6 +217,6 @@ pub struct Tag {
     pub name: String,
     pub href: Option<String>,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub icon: Option<MediaAttachment>,
 }
diff --git a/crates/kitsune-type/src/ap/object.rs b/crates/kitsune-type/src/ap/object.rs
@@ -16,11 +16,11 @@ pub struct MediaAttachment {
     #[serde(deserialize_with = "jsonld::serde::FirstOk::deserialize")]
     pub r#type: MediaAttachmentType,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub name: Option<String>,
     pub media_type: Option<String>,
     #[serde(default)]
-    #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
+    #[serde(deserialize_with = "jsonld::serde::Optional::<jsonld::serde::First<_>>::deserialize")]
     pub blurhash: Option<String>,
     #[serde(deserialize_with = "jsonld::serde::First::deserialize")]
     pub url: String,

diff --git a/crates/kitsune-type/src/jsonld/serde/first.rs b/crates/kitsune-type/src/jsonld/serde/first.rs
@@ -39,6 +39,17 @@ where
     }
 }
 
+// XXX: Intentionally limiting to `First<PhantomData<_>>` rather than `First<_>` to help inference
+// of the type parameter of `Optional::<First<_>>::deserialize`.
+impl<'de, T> Default for First<PhantomData<T>>
+where
+    T: Deserialize<'de>,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl<'de, T> DeserializeSeed<'de> for First<T>
 where
     T: DeserializeSeed<'de>,

diff --git a/crates/kitsune-type/src/jsonld/serde/first_id.rs b/crates/kitsune-type/src/jsonld/serde/first_id.rs
@@ -32,6 +32,15 @@ where
     }
 }
 
+impl<'de, T> Default for FirstId<PhantomData<T>>
+where
+    T: Deserialize<'de>,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl<'de, T> DeserializeSeed<'de> for FirstId<T>
 where
     T: DeserializeSeed<'de>,

diff --git a/crates/kitsune-type/src/jsonld/serde/first_ok.rs b/crates/kitsune-type/src/jsonld/serde/first_ok.rs
@@ -54,6 +54,15 @@ where
     }
 }
 
+impl<'de, T> Default for FirstOk<PhantomData<T>>
+where
+    T: Deserialize<'de>,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl<'de, T> DeserializeSeed<'de> for FirstOk<T>
 where
     T: DeserializeSeed<'de> + Clone,

diff --git a/crates/kitsune-type/src/jsonld/serde/id.rs b/crates/kitsune-type/src/jsonld/serde/id.rs
@@ -43,6 +43,15 @@ where
     }
 }
 
+impl<'de, T> Default for Id<PhantomData<T>>
+where
+    T: Deserialize<'de>,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl<'de, T> DeserializeSeed<'de> for Id<T>
 where
     T: DeserializeSeed<'de>,

diff --git a/crates/kitsune-type/src/jsonld/serde/id_set.rs b/crates/kitsune-type/src/jsonld/serde/id_set.rs
@@ -32,6 +32,15 @@ where
     }
 }
 
+impl<'de, T> Default for IdSet<PhantomData<T>>
+where
+    T: Deserialize<'de>,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl<'de, T> DeserializeSeed<'de> for IdSet<T>
 where
     T: DeserializeSeed<'de>,

diff --git a/crates/kitsune-type/src/jsonld/serde/mod.rs b/crates/kitsune-type/src/jsonld/serde/mod.rs
@@ -160,13 +160,15 @@ mod first_id;
 mod first_ok;
 mod id;
 mod id_set;
+mod optional;
 mod set;
 
 pub use self::first::First;
 pub use self::first_id::FirstId;
 pub use self::first_ok::FirstOk;
 pub use self::id::Id;
 pub use self::id_set::IdSet;
+pub use self::optional::Optional;
 pub use self::set::Set;
 
 use core::{
@@ -375,7 +377,7 @@ where
 
 #[cfg(test)]
 mod tests {
-    use super::{First, FirstId, FirstOk, IdSet};
+    use super::{First, FirstId, FirstOk, IdSet, Optional};
     use serde::Deserialize;
 
     /// Checks that the types work for some random real-world-ish use cases.
@@ -395,10 +397,10 @@ mod tests {
             #[serde(deserialize_with = "FirstId::deserialize")]
             attributed_to: String,
             #[serde(default)]
-            #[serde(deserialize_with = "First::deserialize")]
+            #[serde(deserialize_with = "Optional::<First<_>>::deserialize")]
             summary: Option<String>,
             #[serde(default)]
-            #[serde(deserialize_with = "First::deserialize")]
+            #[serde(deserialize_with = "Optional::<First<_>>::deserialize")]
             content: Option<String>,
             #[serde(default)]
             #[serde(deserialize_with = "IdSet::deserialize")]

diff --git a/crates/kitsune-type/src/jsonld/serde/optional.rs b/crates/kitsune-type/src/jsonld/serde/optional.rs
@@ -0,0 +1,79 @@
+use core::fmt::{self, Formatter};
+use serde::de::{self, DeserializeSeed, Deserializer};
+
+/// Deserialises an `Option<T::Value>` value.
+///
+/// Workaround until Serde introduces a native mechanism for applying the
+/// `#[serde(deserialize_with)]` attribute to the type inside an `Option<_>`.
+///
+/// cf. <https://github.com/serde-rs/serde/issues/723>.
+pub struct Optional<T> {
+    seed: T,
+}
+
+struct Visitor<T>(T);
+
+impl<'de, T> Optional<T>
+where
+    T: DeserializeSeed<'de> + Default,
+{
+    pub fn new() -> Self {
+        Self::with_seed(T::default())
+    }
+
+    pub fn deserialize<D>(deserializer: D) -> Result<Option<T::Value>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Self::new().deserialize(deserializer)
+    }
+}
+
+impl<'de, T> Optional<T>
+where
+    T: DeserializeSeed<'de>,
+{
+    pub fn with_seed(seed: T) -> Self {
+        Self { seed }
+    }
+}
+
+impl<'de, T> DeserializeSeed<'de> for Optional<T>
+where
+    T: DeserializeSeed<'de>,
+{
+    type Value = Option<T::Value>;
+
+    fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_option(Visitor(self.seed))
+    }
+}
+
+impl<'de, T> de::Visitor<'de> for Visitor<T>
+where
+    T: DeserializeSeed<'de>,
+{
+    type Value = Option<T::Value>;
+
+    fn expecting(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        f.write_str("option")
+    }
+
+    fn visit_unit<E>(self) -> Result<Self::Value, E> {
+        Ok(None)
+    }
+
+    fn visit_none<E>(self) -> Result<Self::Value, E> {
+        Ok(None)
+    }
+
+    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        self.0.deserialize(deserializer).map(Some)
+    }
+}
diff --git a/crates/kitsune-type/src/jsonld/serde/set.rs b/crates/kitsune-type/src/jsonld/serde/set.rs
@@ -45,6 +45,15 @@ where
     }
 }
 
+impl<'de, T> Default for Set<PhantomData<T>>
+where
+    T: Deserialize<'de>,
+{
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl<'de, T> DeserializeSeed<'de> for Set<T>
 where
     T: DeserializeSeed<'de>,