# Objective
- A common bevy pattern is to pre-allocate a weak `Handle` with a
static, random ID and fill it during `Plugin::build` via
`load_internal_asset!`
- This requires generating a random 128-bit number that is interpreted
as a UUID. This is much less convenient than generating a UUID directly,
and also, strictly speaking, error prone, since it often results in an
invalid UUIDv4 – they have to follow the pattern
`xxxxxxxx-xxxx-4xxx-xxxx-xxxxxxxxxxxx`, where `x` is a random nibble (in
practice this doesn't matter, since the UUID is just interpreted as a
bag of bytes).
## Solution
- Add a `weak_handle!` macro that internally calls
[`uuid::uuid!`](https://docs.rs/uuid/1.12.0/uuid/macro.uuid.html) to
parse a UUID from a string literal.
- Now any random UUID generation tool can be used to generate an asset
ID, such as `uuidgen` or entering "uuid" in DuckDuckGo.
Previously:
```rust
const SHADER: Handle<Shader> = Handle::weak_from_u128(314685653797097581405914117016993910609);
```
After this PR:
```rust
const SHADER: Handle<Shader> = weak_handle!("1347c9b7-c46a-48e7-b7b8-023a354b7cac");
```
Note that I did not yet migrate any of the existing uses. I can do that
if desired, but want to have some feedback first to avoid wasted effort.
## Testing
Tested via the included doctest.
ff466a37df