bevy/crates/bevy_ecs
Alexander Sepity d3e020a1e7 System sets and run criteria v2 (#1675)
I'm opening this prematurely; consider this an RFC that predates RFCs and therefore not super-RFC-like.

This PR does two "big" things: decouple run criteria from system sets, reimagine system sets as weapons of mass system description.

### What it lets us do:

* Reuse run criteria within a stage.
* Pipe output of one run criteria as input to another.
* Assign labels, dependencies, run criteria, and ambiguity sets to many systems at the same time.

### Things already done:
* Decoupled run criteria from system sets.
* Mass system description superpowers to `SystemSet`.
* Implemented `RunCriteriaDescriptor`.
* Removed `VirtualSystemSet`.
* Centralized all run criteria of `SystemStage`.
* Extended system descriptors with per-system run criteria.
* `.before()` and `.after()` for run criteria.
* Explicit order between state driver and related run criteria. Fixes #1672.
* Opt-in run criteria deduplication; default behavior is to panic.
* Labels (not exposed) for state run criteria; state run criteria are deduplicated.

### API issues that need discussion:

* [`FixedTimestep::step(1.0).label("my label")`](eaccf857cd/crates/bevy_ecs/src/schedule/run_criteria.rs (L120-L122)) and [`FixedTimestep::step(1.0).with_label("my label")`](eaccf857cd/crates/bevy_core/src/time/fixed_timestep.rs (L86-L89)) are both valid but do very different things.

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I will try to maintain this post up-to-date as things change. Do check the diffs in "edited" thingy from time to time.

Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2021-03-24 20:11:55 +00:00
..
macros System sets and run criteria v2 (#1675) 2021-03-24 20:11:55 +00:00
src System sets and run criteria v2 (#1675) 2021-03-24 20:11:55 +00:00
Cargo.toml Update fixedbitset requirement from 0.3 to 0.4 (#1726) 2021-03-22 07:06:04 +00:00