DynamicTupleStruct does not mirror the hashability of its underlying type

[UkoeHB]

Bevy version

Bevy v0.16.0.

What you did

Tried to reflect-deserialize a type containing HashMap<TileId, ...> where:

#[derive(Component, Debug, Clone, Deserialize, Eq, PartialEq, Hash, Reflect)]
#[component(immutable)]
pub struct TileId(Cow<'static, str>);

Specifically I have data stored in an asset and do:

• Parse asset into data representation (think json::Value).
• Use TypedReflectDeserializer to deserialize the value. <-- this is where it all goes wrong
• Use T::from_reflect(value.as_partial_reflect()) to get the final type.

What went wrong

Received this panic:

bevy_reflect-0.16.0/src/map.rs:259:30:
the dynamic type `bevy_reflect::DynamicTupleStruct` (representing `game_core::map::data::TileId`) does not support hashing

Additional information

• Adding #[reflect(Hash)] did not change the error, but adding #[reflect(Hash, Deserialize)] does fix it.
• Switching to TileId(String) did not change the error.
• Removing #[component(immutable)] did not change the error.

The bug seems to be that when TileId is represented as DynamicTupleStruct, its hashability is lost unless you do #[reflect(Hash, Deserialize)]. At minimum we need a better error message to give people a solution.

[gwafotapa]

I have a similar issue. I solved it by adding #[reflect(Hash, Deserialize)] to the key. I don't have a good understanding of how Reflect works though so it may be a bad idea.

[UkoeHB]

I solved it by adding #[reflect(Hash, Deserialize)] to the key.

This worked, thanks!