Making the deserialization for LinkedHashMap generic for build hasher type

Author: robinbernon

Cargo.toml

@@ -22,3 +22,4 @@ serde = { version = "1.0", optional = true }
 
 [dev-dependencies]
 serde_test = "1.0"
+fxhash = "0.2.1"

src/serde.rs

@@ -31,54 +31,59 @@ where
     }
 }
 
-#[derive(Debug)]
-pub struct LinkedHashMapVisitor<K, V> {
-    marker: PhantomData<LinkedHashMap<K, V>>,
-}
-
-impl<K, V> LinkedHashMapVisitor<K, V> {
-    fn new() -> Self {
-        LinkedHashMapVisitor {
-            marker: PhantomData,
-        }
-    }
-}
-
-impl<K, V> Default for LinkedHashMapVisitor<K, V> {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
-impl<'de, K, V> Visitor<'de> for LinkedHashMapVisitor<K, V>
+impl<'de, K, V, S> Deserialize<'de> for LinkedHashMap<K, V, S>
 where
     K: Deserialize<'de> + Eq + Hash,
     V: Deserialize<'de>,
+    S: BuildHasher + Default,
 {
-    type Value = LinkedHashMap<K, V>;
-
-    fn expecting(&self, formatter: &mut Formatter) -> fmt::Result {
-        write!(formatter, "a map")
-    }
+    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
+        #[derive(Debug)]
+        pub struct LinkedHashMapVisitor<K, V, S> {
+            marker: PhantomData<LinkedHashMap<K, V, S>>,
+        }
 
-    #[inline]
-    fn visit_map<M: MapAccess<'de>>(self, mut map: M) -> Result<Self::Value, M::Error> {
-        let mut values = LinkedHashMap::with_capacity(map.size_hint().unwrap_or(0));
+        impl<K, V, S> LinkedHashMapVisitor<K, V, S> {
+            fn new() -> Self {
+                LinkedHashMapVisitor {
+                    marker: PhantomData,
+                }
+            }
+        }
 
-        while let Some((k, v)) = map.next_entry()? {
-            values.insert(k, v);
+        impl<K, V, S> Default for LinkedHashMapVisitor<K, V, S> {
+            fn default() -> Self {
+                Self::new()
+            }
         }
 
-        Ok(values)
-    }
-}
+        impl<'de, K, V, S> Visitor<'de> for LinkedHashMapVisitor<K, V, S>
+        where
+            K: Deserialize<'de> + Eq + Hash,
+            V: Deserialize<'de>,
+            S: BuildHasher + Default,
+        {
+            type Value = LinkedHashMap<K, V, S>;
+
+            fn expecting(&self, formatter: &mut Formatter) -> fmt::Result {
+                write!(formatter, "a map")
+            }
+
+            #[inline]
+            fn visit_map<M: MapAccess<'de>>(self, mut map: M) -> Result<Self::Value, M::Error> {
+                let mut values = LinkedHashMap::with_capacity_and_hasher(
+                    map.size_hint().unwrap_or(0),
+                    S::default(),
+                );
+
+                while let Some((k, v)) = map.next_entry()? {
+                    values.insert(k, v);
+                }
+
+                Ok(values)
+            }
+        }
 
-impl<'de, K, V> Deserialize<'de> for LinkedHashMap<K, V>
-where
-    K: Deserialize<'de> + Eq + Hash,
-    V: Deserialize<'de>,
-{
-    fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
         deserializer.deserialize_map(LinkedHashMapVisitor::default())
     }
 }

tests/serde.rs

@@ -1,5 +1,6 @@
 #![cfg(feature = "serde_impl")]
 
+use fxhash::FxBuildHasher;
 use hashlink::{LinkedHashMap, LinkedHashSet};
 use serde_test::{assert_tokens, Token};
 
@@ -32,6 +33,35 @@ fn map_serde_tokens() {
     );
 }
 
+#[test]
+fn map_serde_tokens_empty_generic() {
+    let map = LinkedHashMap::<char, u32>::new();
+
+    assert_tokens(&map, &[Token::Map { len: Some(0) }, Token::MapEnd]);
+}
+
+#[test]
+fn map_serde_tokens_generic() {
+    let mut map = LinkedHashMap::with_hasher(FxBuildHasher::default());
+    map.insert('a', 10);
+    map.insert('b', 20);
+    map.insert('c', 30);
+
+    assert_tokens(
+        &map,
+        &[
+            Token::Map { len: Some(3) },
+            Token::Char('a'),
+            Token::I32(10),
+            Token::Char('b'),
+            Token::I32(20),
+            Token::Char('c'),
+            Token::I32(30),
+            Token::MapEnd,
+        ],
+    );
+}
+
 #[test]
 fn set_serde_tokens_empty() {
     let set = LinkedHashSet::<u32>::new();