Add support for hashbrown v0.16 (#888)

Author: jonasbb

.github/workflows/ci.yaml

@@ -89,7 +89,7 @@ jobs:
       - name: "Check no_std+alloc (No Default Features / ${{ matrix.os }} / ${{ matrix.rust }})"
         run: cargo check --package serde_with --no-default-features --features=alloc --target thumbv7em-none-eabihf
       - name: "Check no_std+alloc+optional (No Default Features / ${{ matrix.os }} / ${{ matrix.rust }})"
-        run: cargo check --package serde_with --no-default-features --features=alloc,base64,chrono_0_4,hashbrown_0_14,hashbrown_0_15,hex,indexmap_1,indexmap_2,json,time_0_3 --target thumbv7em-none-eabihf
+        run: cargo check --package serde_with --no-default-features --features=alloc,base64,chrono_0_4,hashbrown_0_14,hashbrown_0_15,hashbrown_0_16,hex,indexmap_1,indexmap_2,json,time_0_3 --target thumbv7em-none-eabihf
 
       # The tests are split into build and run steps, to see the time impact of each
       # cargo test --all-targets does NOT run doctests

Cargo.lock

@@ -28,6 +28,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
     );
     ```
 
+* Add support for `hashbrown` v0.16 (#877)
+
+    This extends the existing support for `hashbrown` v0.14 and v0.15 to the newly released version.
+
 ## [3.14.1] - 2025-09-19
 
 ### Fixed

serde_with/CHANGELOG.md

@@ -81,6 +81,12 @@ hashbrown_0_14 = ["dep:hashbrown_0_14", "alloc"]
 ## It enables the `alloc` feature.
 ## Some functionality is only available when `std` is enabled too.
 hashbrown_0_15 = ["dep:hashbrown_0_15", "alloc"]
+## The feature enables `hashbrown::{HashMap, HashSet}` as supported containers.
+##
+## This pulls in [`hashbrown` v0.16](::hashbrown_0_16) as a dependency.
+## It enables the `alloc` feature.
+## Some functionality is only available when `std` is enabled too.
+hashbrown_0_16 = ["dep:hashbrown_0_16", "alloc"]
 ## The feature enables serializing data in hex format.
 ##
 ## This pulls in [`hex`] as a dependency.
@@ -148,6 +154,7 @@ chrono_0_4 = { package = "chrono", version = "0.4.20", optional = true, default-
 document-features = { version = "0.2.7", optional = true }
 hashbrown_0_14 = { package = "hashbrown", version = "0.14.0", optional = true, default-features = false, features = ["serde"] }
 hashbrown_0_15 = { package = "hashbrown", version = "0.15.0", optional = true, default-features = false, features = ["serde"] }
+hashbrown_0_16 = { package = "hashbrown", version = "0.16.0", optional = true, default-features = false, features = ["serde"] }
 hex = { version = "0.4.3", optional = true, default-features = false }
 indexmap_1 = { package = "indexmap", version = "1.8", optional = true, default-features = false, features = ["serde-1"] }
 indexmap_2 = { package = "indexmap", version = "2.0", optional = true, default-features = false, features = ["serde"] }
@@ -206,6 +213,11 @@ name = "hashbrown_0_15"
 path = "tests/hashbrown_0_15.rs"
 required-features = ["hashbrown_0_15", "macros"]
 
+[[test]]
+name = "hashbrown_0_16"
+path = "tests/hashbrown_0_16.rs"
+required-features = ["hashbrown_0_16", "macros"]
+
 [[test]]
 name = "indexmap_1"
 path = "tests/indexmap_1.rs"

serde_with/Cargo.toml

@@ -10,6 +10,8 @@ use crate::{
 use hashbrown_0_14::{HashMap as HashbrownMap014, HashSet as HashbrownSet014};
 #[cfg(feature = "hashbrown_0_15")]
 use hashbrown_0_15::{HashMap as HashbrownMap015, HashSet as HashbrownSet015};
+#[cfg(feature = "hashbrown_0_16")]
+use hashbrown_0_16::{HashMap as HashbrownMap016, HashSet as HashbrownSet016};
 #[cfg(feature = "indexmap_1")]
 use indexmap_1::{IndexMap, IndexSet};
 #[cfg(feature = "indexmap_2")]

serde_with/src/de/duplicates.rs

@@ -4,6 +4,8 @@ use crate::{formats::*, prelude::*};
 use hashbrown_0_14::{HashMap as HashbrownMap014, HashSet as HashbrownSet014};
 #[cfg(feature = "hashbrown_0_15")]
 use hashbrown_0_15::{HashMap as HashbrownMap015, HashSet as HashbrownSet015};
+#[cfg(feature = "hashbrown_0_16")]
+use hashbrown_0_16::{HashMap as HashbrownMap016, HashSet as HashbrownSet016};
 #[cfg(feature = "indexmap_1")]
 use indexmap_1::{IndexMap, IndexSet};
 #[cfg(feature = "indexmap_2")]
@@ -39,6 +41,11 @@ pub(crate) mod macros {
                 HashbrownMap015<K: Eq + Hash, V, S: BuildHasher + Default>,
                 (|size| HashbrownMap015::with_capacity_and_hasher(size, Default::default()))
             );
+            #[cfg(feature = "hashbrown_0_16")]
+            $m!(
+                HashbrownMap016<K: Eq + Hash, V, S: BuildHasher + Default>,
+                (|size| HashbrownMap016::with_capacity_and_hasher(size, Default::default()))
+            );
             #[cfg(feature = "indexmap_1")]
             $m!(
                 IndexMap<K: Eq + Hash, V, S: BuildHasher + Default>,
@@ -74,6 +81,12 @@ pub(crate) mod macros {
                 (|size| HashbrownSet015::with_capacity_and_hasher(size, S::default())),
                 insert
             );
+            #[cfg(feature = "hashbrown_0_16")]
+            $m!(
+                HashbrownSet016<T: Eq + Hash, S: BuildHasher + Default>,
+                (|size| HashbrownSet016::with_capacity_and_hasher(size, S::default())),
+                insert
+            );
             #[cfg(feature = "indexmap_1")]
             $m!(
                 IndexSet<T: Eq + Hash, S: BuildHasher + Default>,

serde_with/src/de/impls.rs

@@ -4,6 +4,8 @@ use crate::prelude::*;
 use hashbrown_0_14::HashMap as HashbrownMap014;
 #[cfg(feature = "hashbrown_0_15")]
 use hashbrown_0_15::HashMap as HashbrownMap015;
+#[cfg(feature = "hashbrown_0_16")]
+use hashbrown_0_16::HashMap as HashbrownMap016;
 #[cfg(feature = "indexmap_1")]
 use indexmap_1::IndexMap;
 #[cfg(feature = "indexmap_2")]

serde_with/src/de/skip_error.rs

@@ -74,6 +74,26 @@ where
     }
 }
 
+#[cfg(feature = "hashbrown_0_16")]
+impl<T, S> PreventDuplicateInsertsSet<T> for hashbrown_0_16::HashSet<T, S>
+where
+    T: Eq + Hash,
+    S: BuildHasher + Default,
+{
+    #[inline]
+    fn new(size_hint: Option<usize>) -> Self {
+        match size_hint {
+            Some(size) => Self::with_capacity_and_hasher(size, S::default()),
+            None => Self::with_hasher(S::default()),
+        }
+    }
+
+    #[inline]
+    fn insert(&mut self, value: T) -> bool {
+        self.insert(value)
+    }
+}
+
 #[cfg(feature = "indexmap_1")]
 impl<T, S> PreventDuplicateInsertsSet<T> for indexmap_1::IndexSet<T, S>
 where
@@ -189,6 +209,26 @@ where
     }
 }
 
+#[cfg(feature = "hashbrown_0_16")]
+impl<K, V, S> PreventDuplicateInsertsMap<K, V> for hashbrown_0_16::HashMap<K, V, S>
+where
+    K: Eq + Hash,
+    S: BuildHasher + Default,
+{
+    #[inline]
+    fn new(size_hint: Option<usize>) -> Self {
+        match size_hint {
+            Some(size) => Self::with_capacity_and_hasher(size, S::default()),
+            None => Self::with_hasher(S::default()),
+        }
+    }
+
+    #[inline]
+    fn insert(&mut self, key: K, value: V) -> bool {
+        self.insert(key, value).is_none()
+    }
+}
+
 #[cfg(feature = "indexmap_1")]
 impl<K, V, S> PreventDuplicateInsertsMap<K, V> for indexmap_1::IndexMap<K, V, S>
 where

serde_with/src/duplicate_key_impls/error_on_duplicate.rs

@@ -91,6 +91,34 @@ where
     }
 }
 
+#[cfg(feature = "hashbrown_0_16")]
+impl<K, V, S> DuplicateInsertsFirstWinsMap<K, V> for hashbrown_0_16::HashMap<K, V, S>
+where
+    K: Eq + Hash,
+    S: BuildHasher + Default,
+{
+    #[inline]
+    fn new(size_hint: Option<usize>) -> Self {
+        match size_hint {
+            Some(size) => Self::with_capacity_and_hasher(size, S::default()),
+            None => Self::with_hasher(S::default()),
+        }
+    }
+
+    #[inline]
+    fn insert(&mut self, key: K, value: V) {
+        use hashbrown_0_16::hash_map::Entry;
+
+        match self.entry(key) {
+            // we want to keep the first value, so do nothing
+            Entry::Occupied(_) => {}
+            Entry::Vacant(vacant) => {
+                vacant.insert(value);
+            }
+        }
+    }
+}
+
 #[cfg(feature = "indexmap_1")]
 impl<K, V, S> DuplicateInsertsFirstWinsMap<K, V> for indexmap_1::IndexMap<K, V, S>
 where

serde_with/src/duplicate_key_impls/first_value_wins.rs

@@ -70,6 +70,27 @@ where
     }
 }
 
+#[cfg(feature = "hashbrown_0_16")]
+impl<T, S> DuplicateInsertsLastWinsSet<T> for hashbrown_0_16::HashSet<T, S>
+where
+    T: Eq + Hash,
+    S: BuildHasher + Default,
+{
+    #[inline]
+    fn new(size_hint: Option<usize>) -> Self {
+        match size_hint {
+            Some(size) => Self::with_capacity_and_hasher(size, S::default()),
+            None => Self::with_hasher(S::default()),
+        }
+    }
+
+    #[inline]
+    fn replace(&mut self, value: T) {
+        // Hashset already fulfils the contract
+        self.replace(value);
+    }
+}
+
 #[cfg(feature = "indexmap_1")]
 impl<T, S> DuplicateInsertsLastWinsSet<T> for indexmap_1::IndexSet<T, S>
 where