Decouple some dependencies (#3886)

# Objective

Reduce from scratch build time.

## Solution

Reduce the size of the critical path by removing dependencies between crates where not necessary. For `cargo check --no-default-features` this reduced build time from ~51s to ~45s. For some commits I am not completely sure if the tradeoff between build time reduction and convenience caused by the commit is acceptable. If not, I can drop them.

crates/bevy_derive/src/enum_variant_meta.rs

@@ -1,4 +1,3 @@
-use bevy_macro_utils::BevyManifest;
 use proc_macro::{Span, TokenStream};
 use quote::quote;
 use syn::{parse_macro_input, Data, DeriveInput};
@@ -14,8 +13,6 @@ pub fn derive_enum_variant_meta(input: TokenStream) -> TokenStream {
         }
     };
 
-    let bevy_util_path = BevyManifest::default().get_path(crate::modules::BEVY_UTILS);
-
     let generics = ast.generics;
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
 
@@ -25,13 +22,13 @@ pub fn derive_enum_variant_meta(input: TokenStream) -> TokenStream {
     let indices = 0..names.len();
 
     TokenStream::from(quote! {
-        impl #impl_generics #bevy_util_path::EnumVariantMeta for #struct_name #ty_generics #where_clause {
+        impl #impl_generics #struct_name #ty_generics #where_clause {
-            fn enum_variant_index(&self) -> usize {
+            pub fn enum_variant_index(&self) -> usize {
                 match self {
                     #(#struct_name::#idents {..} => #indices,)*
                 }
             }
-            fn enum_variant_name(&self) -> &'static str {
+            pub fn enum_variant_name(&self) -> &'static str {
                 static variants: &[&str] = &[
                     #(#names,)*
                 ];

crates/bevy_derive/src/lib.rs

@@ -4,7 +4,6 @@ mod app_plugin;
 mod bevy_main;
 mod derefs;
 mod enum_variant_meta;
-mod modules;
 
 use bevy_macro_utils::{derive_label, BevyManifest};
 use proc_macro::TokenStream;

crates/bevy_derive/src/modules.rs

@@ -1 +0,0 @@
-pub const BEVY_UTILS: &str = "bevy_utils";

crates/bevy_ecs/Cargo.toml

@@ -22,7 +22,6 @@ bevy_ecs_macros = { path = "macros", version = "0.8.0-dev" }
 async-channel = "1.4"
 fixedbitset = "0.4"
 fxhash = "0.2"
-thiserror = "1.0"
 downcast-rs = "1.2"
 serde = "1"
 

crates/bevy_ecs/src/entity/map_entities.rs

@@ -1,13 +1,24 @@
 use crate::entity::Entity;
 use bevy_utils::{Entry, HashMap};
-use thiserror::Error;
+use std::fmt;
 
-#[derive(Error, Debug)]
+#[derive(Debug)]
 pub enum MapEntitiesError {
-    #[error("the given entity does not exist in the map")]
     EntityNotFound(Entity),
 }
 
+impl std::error::Error for MapEntitiesError {}
+
+impl fmt::Display for MapEntitiesError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            MapEntitiesError::EntityNotFound(_) => {
+                write!(f, "the given entity does not exist in the map")
+            }
+        }
+    }
+}
+
 pub trait MapEntities {
     fn map_entities(&mut self, entity_map: &EntityMap) -> Result<(), MapEntitiesError>;
 }

crates/bevy_ecs/src/query/state.rs

@@ -12,7 +12,7 @@ use crate::{
 };
 use bevy_tasks::TaskPool;
 use fixedbitset::FixedBitSet;
-use thiserror::Error;
+use std::fmt;
 
 /// Provides scoped access to a [`World`] state according to a given [`WorldQuery`] and query filter.
 pub struct QueryState<Q: WorldQuery, F: WorldQuery = ()>
@@ -936,16 +936,29 @@ where
 
 /// An error that occurs when retrieving a specific [`Entity`]'s query result.
 // TODO: return the type_name as part of this error
-#[derive(Error, Debug, PartialEq, Clone, Copy)]
+#[derive(Debug, PartialEq, Clone, Copy)]
 pub enum QueryEntityError {
-    #[error("The given entity does not have the requested component.")]
     QueryDoesNotMatch(Entity),
-    #[error("The requested entity does not exist.")]
     NoSuchEntity(Entity),
-    #[error("The entity was requested mutably more than once.")]
     AliasedMutability(Entity),
 }
 
+impl std::error::Error for QueryEntityError {}
+
+impl fmt::Display for QueryEntityError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            QueryEntityError::QueryDoesNotMatch(_) => {
+                write!(f, "The given entity does not have the requested component.")
+            }
+            QueryEntityError::NoSuchEntity(_) => write!(f, "The requested entity does not exist."),
+            QueryEntityError::AliasedMutability(_) => {
+                write!(f, "The entity was requested mutably more than once.")
+            }
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::{prelude::*, query::QueryEntityError};

crates/bevy_ecs/src/schedule/state.rs

@@ -5,8 +5,11 @@ use crate::{
     },
     system::{In, IntoChainSystem, Local, Res, ResMut},
 };
-use std::{any::TypeId, fmt::Debug, hash::Hash};
+use std::{
-use thiserror::Error;
+    any::TypeId,
+    fmt::{self, Debug},
+    hash::Hash,
+};
 
 pub trait StateData: Send + Sync + Clone + Eq + Debug + Hash + 'static {}
 impl<T> StateData for T where T: Send + Sync + Clone + Eq + Debug + Hash + 'static {}
@@ -399,16 +402,32 @@ where
     }
 }
 
-#[derive(Debug, Error)]
+#[derive(Debug)]
 pub enum StateError {
-    #[error("Attempted to change the state to the current state.")]
     AlreadyInState,
-    #[error("Attempted to queue a state change, but there was already a state queued.")]
     StateAlreadyQueued,
-    #[error("Attempted to queue a pop, but there is nothing to pop.")]
     StackEmpty,
 }
 
+impl std::error::Error for StateError {}
+
+impl fmt::Display for StateError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            StateError::AlreadyInState => {
+                write!(f, "Attempted to change the state to the current state.")
+            }
+            StateError::StateAlreadyQueued => write!(
+                f,
+                "Attempted to queue a state change, but there was already a state queued."
+            ),
+            StateError::StackEmpty => {
+                write!(f, "Attempted to queue a pop, but there is nothing to pop.")
+            }
+        }
+    }
+}
+
 fn should_run_adapter<T: StateData>(In(cmp_result): In<bool>, state: Res<State<T>>) -> ShouldRun {
     if state.end_next_loop {
         return ShouldRun::No;

crates/bevy_ecs/src/system/query.rs

@@ -9,7 +9,6 @@ use crate::{
 };
 use bevy_tasks::TaskPool;
 use std::{any::TypeId, fmt::Debug};
-use thiserror::Error;
 
 /// Provides scoped access to components in a [`World`].
 ///
@@ -1157,28 +1156,61 @@ where
 }
 
 /// An error that occurs when retrieving a specific [`Entity`]'s component from a [`Query`]
-#[derive(Error, Debug)]
+#[derive(Debug)]
 pub enum QueryComponentError {
-    #[error("This query does not have read access to the requested component.")]
     MissingReadAccess,
-    #[error("This query does not have write access to the requested component.")]
     MissingWriteAccess,
-    #[error("The given entity does not have the requested component.")]
     MissingComponent,
-    #[error("The requested entity does not exist.")]
     NoSuchEntity,
 }
 
+impl std::error::Error for QueryComponentError {}
+
+impl std::fmt::Display for QueryComponentError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            QueryComponentError::MissingReadAccess => {
+                write!(
+                    f,
+                    "This query does not have read access to the requested component."
+                )
+            }
+            QueryComponentError::MissingWriteAccess => {
+                write!(
+                    f,
+                    "This query does not have write access to the requested component."
+                )
+            }
+            QueryComponentError::MissingComponent => {
+                write!(f, "The given entity does not have the requested component.")
+            }
+            QueryComponentError::NoSuchEntity => {
+                write!(f, "The requested entity does not exist.")
+            }
+        }
+    }
+}
+
 /// An error that occurs when evaluating a [`Query`] as a single expected resulted via
 /// [`Query::single`] or [`Query::single_mut`].
-#[derive(Debug, Error)]
+#[derive(Debug)]
 pub enum QuerySingleError {
-    #[error("No entities fit the query {0}")]
     NoEntities(&'static str),
-    #[error("Multiple entities fit the query {0}!")]
     MultipleEntities(&'static str),
 }
 
+impl std::error::Error for QuerySingleError {}
+
+impl std::fmt::Display for QuerySingleError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            QuerySingleError::NoEntities(query) => write!(f, "No entities fit the query {}", query),
+            QuerySingleError::MultipleEntities(query) => {
+                write!(f, "Multiple entities fit the query {}!", query)
+            }
+        }
+    }
+}
 impl<'w, 's, Q: WorldQuery, F: WorldQuery> Query<'w, 's, Q, F>
 where
     F::Fetch: FilterFetch,

crates/bevy_macro_utils/Cargo.toml

@@ -9,6 +9,6 @@ license = "MIT OR Apache-2.0"
 keywords = ["bevy"]
 
 [dependencies]
-cargo-manifest = "0.2.6"
+toml = "0.5.8"
 syn = "1.0"
 quote = "1.0"

crates/bevy_macro_utils/src/lib.rs

@@ -8,13 +8,13 @@ pub use attrs::*;
 pub use shape::*;
 pub use symbol::*;
 
-use cargo_manifest::{DepsSet, Manifest};
 use proc_macro::TokenStream;
 use quote::quote;
 use std::{env, path::PathBuf};
+use toml::{map::Map, Value};
 
 pub struct BevyManifest {
-    manifest: Manifest,
+    manifest: Map<String, Value>,
 }
 
 impl Default for BevyManifest {
@@ -24,7 +24,8 @@ impl Default for BevyManifest {
                 .map(PathBuf::from)
                 .map(|mut path| {
                     path.push("Cargo.toml");
-                    Manifest::from_path(path).unwrap()
+                    let manifest = std::fs::read_to_string(path).unwrap();
+                    toml::from_str(&manifest).unwrap()
                 })
                 .unwrap(),
         }
@@ -36,13 +37,24 @@ impl BevyManifest {
         const BEVY: &str = "bevy";
         const BEVY_INTERNAL: &str = "bevy_internal";
 
-        let find_in_deps = |deps: &DepsSet| -> Option<syn::Path> {
+        fn dep_package(dep: &Value) -> Option<&str> {
+            if dep.as_str().is_some() {
+                None
+            } else {
+                dep.as_table()
+                    .unwrap()
+                    .get("package")
+                    .map(|name| name.as_str().unwrap())
+            }
+        }
+
+        let find_in_deps = |deps: &Map<String, Value>| -> Option<syn::Path> {
             let package = if let Some(dep) = deps.get(name) {
-                return Some(Self::parse_str(dep.package().unwrap_or(name)));
+                return Some(Self::parse_str(dep_package(dep).unwrap_or(name)));
             } else if let Some(dep) = deps.get(BEVY) {
-                dep.package().unwrap_or(BEVY)
+                dep_package(dep).unwrap_or(BEVY)
             } else if let Some(dep) = deps.get(BEVY_INTERNAL) {
-                dep.package().unwrap_or(BEVY_INTERNAL)
+                dep_package(dep).unwrap_or(BEVY_INTERNAL)
             } else {
                 return None;
             };
@@ -54,8 +66,14 @@ impl BevyManifest {
             Some(path)
         };
 
-        let deps = self.manifest.dependencies.as_ref();
+        let deps = self
-        let deps_dev = self.manifest.dev_dependencies.as_ref();
+            .manifest
+            .get("dependencies")
+            .map(|deps| deps.as_table().unwrap());
+        let deps_dev = self
+            .manifest
+            .get("dev-dependencies")
+            .map(|deps| deps.as_table().unwrap());
 
         deps.and_then(find_in_deps)
             .or_else(|| deps_dev.and_then(find_in_deps))

crates/bevy_reflect/bevy_reflect_derive/Cargo.toml

@@ -17,4 +17,4 @@ bevy_macro_utils = { path = "../../bevy_macro_utils", version = "0.8.0-dev" }
 syn = { version = "1.0", features = ["full"] }
 proc-macro2 = "1.0"
 quote = "1.0"
-uuid = { version = "0.8", features = ["v4", "serde"] }
+uuid = { version = "0.8", features = ["v4"] }

crates/bevy_render/src/mesh/mesh/conversions.rs

@@ -25,7 +25,6 @@
 //! ```
 
 use crate::mesh::VertexAttributeValues;
-use bevy_utils::EnumVariantMeta;
 use thiserror::Error;
 
 #[derive(Debug, Clone, Error)]

crates/bevy_render/src/mesh/mesh/mod.rs

@@ -9,10 +9,11 @@ use crate::{
     renderer::RenderDevice,
 };
 use bevy_core::cast_slice;
+use bevy_derive::EnumVariantMeta;
 use bevy_ecs::system::{lifetimeless::SRes, SystemParamItem};
 use bevy_math::*;
 use bevy_reflect::TypeUuid;
-use bevy_utils::{EnumVariantMeta, Hashed};
+use bevy_utils::Hashed;
 use std::{collections::BTreeMap, hash::Hash};
 use thiserror::Error;
 use wgpu::{

crates/bevy_utils/Cargo.toml

@@ -9,9 +9,8 @@ license = "MIT OR Apache-2.0"
 keywords = ["bevy"]
 
 [dependencies]
-bevy_derive = { path = "../bevy_derive", version = "0.8.0-dev" }
 ahash = "0.7.0"
-tracing = { version = "0.1" }
+tracing = { version = "0.1", default-features = false, features = ["std"] }
 instant = { version = "0.1", features = ["wasm-bindgen"] }
 uuid = { version = "0.8", features = ["v4", "serde"] }
 hashbrown = { version = "0.11", features = ["serde"] }

crates/bevy_utils/src/enum_variant_meta.rs

@@ -1,6 +0,0 @@
-pub use bevy_derive::EnumVariantMeta;
-
-pub trait EnumVariantMeta {
-    fn enum_variant_index(&self) -> usize;
-    fn enum_variant_name(&self) -> &'static str;
-}

crates/bevy_utils/src/lib.rs

@@ -6,12 +6,10 @@ pub mod futures;
 pub mod label;
 
 mod default;
-mod enum_variant_meta;
 mod float_ord;
 
 pub use ahash::AHasher;
 pub use default::default;
-pub use enum_variant_meta::*;
 pub use float_ord::*;
 pub use hashbrown;
 pub use instant::{Duration, Instant};