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bevy_reflect: support map insertion (bevyengine#5173)
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# Objective

This is a rebase of bevyengine#3701 which is currently scheduled for 0.8 but is marked for adoption.

> Fixes bevyengine#3609

## Solution
> - add an `insert_boxed()` method on the `Map` trait
> - implement it for `HashMap` using a new `FromReflect` generic bound
> - add a `map_apply()` helper method to implement `Map::apply()`, that inserts new values instead of ignoring them


---

## Changelog
TODO

Co-authored-by: james7132 <[email protected]>
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@Davier @james7132
Davier and james7132 committed Oct 28, 2022
1 parent e10e84d commit 47496f3
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Showing 5 changed files with 92 additions and 41 deletions.
47 changes: 32 additions & 15 deletions crates/bevy_reflect/src/impls/std.rs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
use crate as bevy_reflect;
use crate::{
map_partial_eq, Array, ArrayInfo, ArrayIter, DynamicMap, FromReflect, FromType,
map_apply, map_partial_eq, Array, ArrayInfo, ArrayIter, DynamicMap, FromReflect, FromType,
GetTypeRegistration, List, ListInfo, Map, MapInfo, MapIter, Reflect, ReflectDeserialize,
ReflectMut, ReflectRef, ReflectSerialize, TypeInfo, TypeRegistration, Typed, ValueInfo,
};
Expand Down Expand Up @@ -193,7 +193,7 @@ impl<T: FromReflect> FromReflect for Vec<T> {
}
}

impl<K: Reflect + Eq + Hash, V: Reflect> Map for HashMap<K, V> {
impl<K: FromReflect + Eq + Hash, V: FromReflect> Map for HashMap<K, V> {
fn get(&self, key: &dyn Reflect) -> Option<&dyn Reflect> {
key.downcast_ref::<K>()
.and_then(|key| HashMap::get(self, key))
Expand Down Expand Up @@ -231,9 +231,34 @@ impl<K: Reflect + Eq + Hash, V: Reflect> Map for HashMap<K, V> {
}
dynamic_map
}

fn insert_boxed(
&mut self,
key: Box<dyn Reflect>,
value: Box<dyn Reflect>,
) -> Option<Box<dyn Reflect>> {
let key = key.take::<K>().unwrap_or_else(|key| {
K::from_reflect(&*key).unwrap_or_else(|| {
panic!(
"Attempted to insert invalid key of type {}.",
key.type_name()
)
})
});
let value = value.take::<V>().unwrap_or_else(|value| {
V::from_reflect(&*value).unwrap_or_else(|| {
panic!(
"Attempted to insert invalid value of type {}.",
value.type_name()
)
})
});
self.insert(key, value)
.map(|old_value| Box::new(old_value) as Box<dyn Reflect>)
}
}

impl<K: Reflect + Eq + Hash, V: Reflect> Reflect for HashMap<K, V> {
impl<K: FromReflect + Eq + Hash, V: FromReflect> Reflect for HashMap<K, V> {
fn type_name(&self) -> &str {
std::any::type_name::<Self>()
}
Expand Down Expand Up @@ -263,15 +288,7 @@ impl<K: Reflect + Eq + Hash, V: Reflect> Reflect for HashMap<K, V> {
}

fn apply(&mut self, value: &dyn Reflect) {
if let ReflectRef::Map(map_value) = value.reflect_ref() {
for (key, value) in map_value.iter() {
if let Some(v) = Map::get_mut(self, key) {
v.apply(value);
}
}
} else {
panic!("Attempted to apply a non-map type to a map type.");
}
map_apply(self, value);
}

fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> {
Expand All @@ -296,7 +313,7 @@ impl<K: Reflect + Eq + Hash, V: Reflect> Reflect for HashMap<K, V> {
}
}

impl<K: Reflect + Eq + Hash, V: Reflect> Typed for HashMap<K, V> {
impl<K: FromReflect + Eq + Hash, V: FromReflect> Typed for HashMap<K, V> {
fn type_info() -> &'static TypeInfo {
static CELL: GenericTypeInfoCell = GenericTypeInfoCell::new();
CELL.get_or_insert::<Self, _>(|| TypeInfo::Map(MapInfo::new::<Self, K, V>()))
Expand All @@ -305,8 +322,8 @@ impl<K: Reflect + Eq + Hash, V: Reflect> Typed for HashMap<K, V> {

impl<K, V> GetTypeRegistration for HashMap<K, V>
where
K: Reflect + Clone + Eq + Hash + for<'de> Deserialize<'de>,
V: Reflect + Clone + for<'de> Deserialize<'de>,
K: FromReflect + Clone + Eq + Hash + for<'de> Deserialize<'de>,
V: FromReflect + Clone + for<'de> Deserialize<'de>,
{
fn get_type_registration() -> TypeRegistration {
let mut registration = TypeRegistration::of::<Self>();
Expand Down
3 changes: 3 additions & 0 deletions crates/bevy_reflect/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -353,6 +353,7 @@ mod tests {

let mut map = DynamicMap::default();
map.insert(2usize, 3i8);
map.insert(3usize, 4i8);
foo_patch.insert("d", map);

let mut bar_patch = DynamicStruct::default();
Expand Down Expand Up @@ -394,6 +395,7 @@ mod tests {
let mut hash_map = HashMap::default();
hash_map.insert(1, 1);
hash_map.insert(2, 3);
hash_map.insert(3, 4);

let mut hash_map_baz = HashMap::default();
hash_map_baz.insert(1, Bar { x: 7 });
Expand All @@ -416,6 +418,7 @@ mod tests {

let mut hash_map = HashMap::default();
hash_map.insert(2, 3);
hash_map.insert(3, 4);

let expected_new_foo = Foo {
a: 2,
Expand Down
74 changes: 52 additions & 22 deletions crates/bevy_reflect/src/map.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,16 @@ pub trait Map: Reflect {

/// Clones the map, producing a [`DynamicMap`].
fn clone_dynamic(&self) -> DynamicMap;

/// Inserts a key-value pair into the map.
///
/// If the map did not have this key present, `None` is returned.
/// If the map did have this key present, the value is updated, and the old value is returned.
fn insert_boxed(
&mut self,
key: Box<dyn Reflect>,
value: Box<dyn Reflect>,
) -> Option<Box<dyn Reflect>>;
}

/// A container for compile-time map info.
Expand Down Expand Up @@ -153,19 +163,6 @@ impl DynamicMap {
pub fn insert<K: Reflect, V: Reflect>(&mut self, key: K, value: V) {
self.insert_boxed(Box::new(key), Box::new(value));
}

/// Inserts a key-value pair of [`Reflect`] values into the map.
pub fn insert_boxed(&mut self, key: Box<dyn Reflect>, value: Box<dyn Reflect>) {
match self.indices.entry(key.reflect_hash().expect(HASH_ERROR)) {
Entry::Occupied(entry) => {
self.values[*entry.get()] = (key, value);
}
Entry::Vacant(entry) => {
entry.insert(self.values.len());
self.values.push((key, value));
}
}
}
}

impl Map for DynamicMap {
Expand Down Expand Up @@ -210,6 +207,25 @@ impl Map for DynamicMap {
.get(index)
.map(|(key, value)| (&**key, &**value))
}

fn insert_boxed(
&mut self,
key: Box<dyn Reflect>,
mut value: Box<dyn Reflect>,
) -> Option<Box<dyn Reflect>> {
match self.indices.entry(key.reflect_hash().expect(HASH_ERROR)) {
Entry::Occupied(entry) => {
let (_old_key, old_value) = self.values.get_mut(*entry.get()).unwrap();
std::mem::swap(old_value, &mut value);
Some(value)
}
Entry::Vacant(entry) => {
entry.insert(self.values.len());
self.values.push((key, value));
None
}
}
}
}

impl Reflect for DynamicMap {
Expand Down Expand Up @@ -245,15 +261,7 @@ impl Reflect for DynamicMap {
}

fn apply(&mut self, value: &dyn Reflect) {
if let ReflectRef::Map(map_value) = value.reflect_ref() {
for (key, value) in map_value.iter() {
if let Some(v) = self.get_mut(key) {
v.apply(value);
}
}
} else {
panic!("Attempted to apply a non-map type to a map type.");
}
map_apply(self, value);
}

fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> {
Expand Down Expand Up @@ -387,6 +395,28 @@ pub fn map_debug(dyn_map: &dyn Map, f: &mut std::fmt::Formatter<'_>) -> std::fmt
debug.finish()
}

/// Applies the elements of reflected map `b` to the corresponding elements of map `a`.
///
/// If a key from `b` does not exist in `a`, the value is cloned and inserted.
///
/// # Panics
///
/// This function panics if `b` is not a reflected map.
#[inline]
pub fn map_apply<M: Map>(a: &mut M, b: &dyn Reflect) {
if let ReflectRef::Map(map_value) = b.reflect_ref() {
for (key, b_value) in map_value.iter() {
if let Some(a_value) = a.get_mut(key) {
a_value.apply(b_value);
} else {
a.insert_boxed(key.clone_value(), b_value.clone_value());
}
}
} else {
panic!("Attempted to apply a non-map type to a map type.");
}
}

#[cfg(test)]
mod tests {
use super::DynamicMap;
Expand Down
7 changes: 4 additions & 3 deletions crates/bevy_reflect/src/reflect.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -93,17 +93,18 @@ pub trait Reflect: Any + Send + Sync {
/// and excess elements in `value` are appended to `self`.
/// - If `T` is a [`Map`], then for each key in `value`, the associated
/// value is applied to the value associated with the same key in `self`.
/// Keys which are not present in both maps are ignored.
/// Keys which are not present in `self` are inserted.
/// - If `T` is none of these, then `value` is downcast to `T`, cloned, and
/// assigned to `self`.
///
/// Note that `Reflect` must be implemented manually for [`List`]s and
/// [`Map`]s in order to achieve the correct semantics, as derived
/// implementations will have the semantics for [`Struct`], [`TupleStruct`]
/// or none of the above depending on the kind of type. For lists, use the
/// [`list_apply`] helper function when implementing this method.
/// or none of the above depending on the kind of type. For lists and maps, use the
/// [`list_apply`] and [`map_apply`] helper functions when implementing this method.
///
/// [`list_apply`]: crate::list_apply
/// [`map_apply`]: crate::map_apply
///
/// # Panics
///
Expand Down
2 changes: 1 addition & 1 deletion crates/bevy_reflect/src/serde/de.rs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
use crate::{
serde::type_fields, DynamicArray, DynamicList, DynamicMap, DynamicStruct, DynamicTuple,
DynamicTupleStruct, Reflect, ReflectDeserialize, TypeRegistry,
DynamicTupleStruct, Map, Reflect, ReflectDeserialize, TypeRegistry,
};
use erased_serde::Deserializer;
use serde::de::{self, DeserializeSeed, MapAccess, SeqAccess, Visitor};
Expand Down

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