make bevy_text optional again (#7801)

# Objective

- `bevy_text` used to be "optional". the feature could be disabled, which meant that the systems were not added but `bevy_text` was still compiled because of a hard dependency in `bevy_ui`
- Running something without `bevy_text` enabled and with `bevy_ui` enabled now crashes:
```
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /bevy/crates/bevy_ecs/src/schedule/schedule.rs:1147:34
```
- This is because `bevy_ui` declares some of its systems in ambiguity sets with systems from `bevy_text`, which were not added if `bevy_text` is disabled

## Solution

- Make `bevy_text` completely optional

## Migration Guide

- feature `bevy_text` now completely removes `bevy_text` from the dependencies when not enabled. Enable feature `bevy_text` if you use Bevy to render text

crates/bevy_internal/Cargo.toml

@@ -82,6 +82,8 @@ dynamic_linking = ["bevy_diagnostic/dynamic_linking"]
 # Enable using a shared stdlib for cxx on Android.
 android_shared_stdcxx = ["bevy_audio/android_shared_stdcxx"]
 
+bevy_text = ["dep:bevy_text", "bevy_ui?/bevy_text"]
+
 [dependencies]
 # bevy
 bevy_app = { path = "../bevy_app", version = "0.9.0" }

crates/bevy_ui/Cargo.toml

@@ -24,7 +24,7 @@ bevy_reflect = { path = "../bevy_reflect", version = "0.9.0", features = [
 ] }
 bevy_render = { path = "../bevy_render", version = "0.9.0" }
 bevy_sprite = { path = "../bevy_sprite", version = "0.9.0" }
-bevy_text = { path = "../bevy_text", version = "0.9.0" }
+bevy_text = { path = "../bevy_text", version = "0.9.0", optional = true }
 bevy_transform = { path = "../bevy_transform", version = "0.9.0" }
 bevy_window = { path = "../bevy_window", version = "0.9.0" }
 bevy_utils = { path = "../bevy_utils", version = "0.9.0" }

crates/bevy_ui/src/lib.rs

@@ -14,7 +14,9 @@ pub mod node_bundles;
 pub mod update;
 pub mod widget;
 
-use bevy_render::{camera::CameraUpdateSystem, extract_component::ExtractComponentPlugin};
+#[cfg(feature = "bevy_text")]
+use bevy_render::camera::CameraUpdateSystem;
+use bevy_render::extract_component::ExtractComponentPlugin;
 pub use flex::*;
 pub use focus::*;
 pub use geometry::*;
@@ -103,44 +105,49 @@ impl Plugin for UiPlugin {
             .configure_set(UiSystem::Focus.in_base_set(CoreSet::PreUpdate))
             .configure_set(UiSystem::Flex.in_base_set(CoreSet::PostUpdate))
             .configure_set(UiSystem::Stack.in_base_set(CoreSet::PostUpdate))
-            .add_system(ui_focus_system.in_set(UiSystem::Focus).after(InputSystem))
-            // add these systems to front because these must run before transform update systems
-            .add_system(
-                widget::text_system
-                    .in_base_set(CoreSet::PostUpdate)
-                    .before(UiSystem::Flex)
-                    // Potential conflict: `Assets<Image>`
-                    // In practice, they run independently since `bevy_render::camera_update_system`
-                    // will only ever observe its own render target, and `widget::text_system`
-                    // will never modify a pre-existing `Image` asset.
-                    .ambiguous_with(CameraUpdateSystem)
-                    // Potential conflict: `Assets<Image>`
-                    // Since both systems will only ever insert new [`Image`] assets,
-                    // they will never observe each other's effects.
-                    .ambiguous_with(bevy_text::update_text2d_layout),
-            )
-            .add_system(
-                widget::update_image_calculated_size_system
-                    .in_base_set(CoreSet::PostUpdate)
-                    .before(UiSystem::Flex)
-                    // Potential conflicts: `Assets<Image>`
-                    // They run independently since `widget::image_node_system` will only ever observe
-                    // its own UiImage, and `widget::text_system` & `bevy_text::update_text2d_layout`
-                    // will never modify a pre-existing `Image` asset.
-                    .ambiguous_with(bevy_text::update_text2d_layout)
-                    .ambiguous_with(widget::text_system),
-            )
-            .add_system(
-                flex_node_system
-                    .in_set(UiSystem::Flex)
-                    .before(TransformSystem::TransformPropagate),
-            )
-            .add_system(ui_stack_system.in_set(UiSystem::Stack))
-            .add_system(
-                update_clipping_system
-                    .after(TransformSystem::TransformPropagate)
-                    .in_base_set(CoreSet::PostUpdate),
-            );
+            .add_system(ui_focus_system.in_set(UiSystem::Focus).after(InputSystem));
+        // add these systems to front because these must run before transform update systems
+        #[cfg(feature = "bevy_text")]
+        app.add_system(
+            widget::text_system
+                .in_base_set(CoreSet::PostUpdate)
+                .before(UiSystem::Flex)
+                // Potential conflict: `Assets<Image>`
+                // In practice, they run independently since `bevy_render::camera_update_system`
+                // will only ever observe its own render target, and `widget::text_system`
+                // will never modify a pre-existing `Image` asset.
+                .ambiguous_with(CameraUpdateSystem)
+                // Potential conflict: `Assets<Image>`
+                // Since both systems will only ever insert new [`Image`] assets,
+                // they will never observe each other's effects.
+                .ambiguous_with(bevy_text::update_text2d_layout),
+        );
+        app.add_system({
+            let system = widget::update_image_calculated_size_system
+                .in_base_set(CoreSet::PostUpdate)
+                .before(UiSystem::Flex);
+            // Potential conflicts: `Assets<Image>`
+            // They run independently since `widget::image_node_system` will only ever observe
+            // its own UiImage, and `widget::text_system` & `bevy_text::update_text2d_layout`
+            // will never modify a pre-existing `Image` asset.
+            #[cfg(feature = "bevy_text")]
+            let system = system
+                .ambiguous_with(bevy_text::update_text2d_layout)
+                .ambiguous_with(widget::text_system);
+
+            system
+        })
+        .add_system(
+            flex_node_system
+                .in_set(UiSystem::Flex)
+                .before(TransformSystem::TransformPropagate),
+        )
+        .add_system(ui_stack_system.in_set(UiSystem::Stack))
+        .add_system(
+            update_clipping_system
+                .after(TransformSystem::TransformPropagate)
+                .in_base_set(CoreSet::PostUpdate),
+        );
 
         crate::render::build_ui_render(app);
     }

crates/bevy_ui/src/node_bundles.rs

@@ -9,6 +9,7 @@ use bevy_render::{
     prelude::{Color, ComputedVisibility},
     view::Visibility,
 };
+#[cfg(feature = "bevy_text")]
 use bevy_text::{Text, TextAlignment, TextSection, TextStyle};
 use bevy_transform::prelude::{GlobalTransform, Transform};
 
@@ -95,6 +96,7 @@ pub struct ImageBundle {
     pub z_index: ZIndex,
 }
 
+#[cfg(feature = "bevy_text")]
 /// A UI node that is text
 #[derive(Bundle, Clone, Debug)]
 pub struct TextBundle {
@@ -128,6 +130,7 @@ pub struct TextBundle {
     pub background_color: BackgroundColor,
 }
 
+#[cfg(feature = "bevy_text")]
 impl Default for TextBundle {
     fn default() -> Self {
         Self {
@@ -147,6 +150,7 @@ impl Default for TextBundle {
     }
 }
 
+#[cfg(feature = "bevy_text")]
 impl TextBundle {
     /// Create a [`TextBundle`] from a single section.
     ///

crates/bevy_ui/src/render/mod.rs

@@ -3,6 +3,7 @@ mod render_pass;
 
 use bevy_core_pipeline::{core_2d::Camera2d, core_3d::Camera3d};
 use bevy_render::ExtractSchedule;
+#[cfg(feature = "bevy_text")]
 use bevy_window::{PrimaryWindow, Window};
 pub use pipeline::*;
 pub use render_pass::*;
@@ -26,7 +27,10 @@ use bevy_render::{
     view::{ComputedVisibility, ExtractedView, ViewUniforms},
     Extract, RenderApp, RenderSet,
 };
-use bevy_sprite::{SpriteAssetEvents, TextureAtlas};
+use bevy_sprite::SpriteAssetEvents;
+#[cfg(feature = "bevy_text")]
+use bevy_sprite::TextureAtlas;
+#[cfg(feature = "bevy_text")]
 use bevy_text::{Text, TextLayoutInfo};
 use bevy_transform::components::GlobalTransform;
 use bevy_utils::FloatOrd;
@@ -78,6 +82,7 @@ pub fn build_ui_render(app: &mut App) {
                 extract_default_ui_camera_view::<Camera2d>,
                 extract_default_ui_camera_view::<Camera3d>,
                 extract_uinodes.in_set(RenderUiSystem::ExtractNode),
+                #[cfg(feature = "bevy_text")]
                 extract_text_uinodes.after(RenderUiSystem::ExtractNode),
             ),
         )
@@ -288,6 +293,7 @@ pub fn extract_default_ui_camera_view<T: Component>(
     }
 }
 
+#[cfg(feature = "bevy_text")]
 pub fn extract_text_uinodes(
     mut extracted_uinodes: ResMut<ExtractedUiNodes>,
     texture_atlases: Extract<Res<Assets<TextureAtlas>>>,

crates/bevy_ui/src/widget/image.rs

@@ -1,17 +1,18 @@
 use crate::{CalculatedSize, UiImage};
 use bevy_asset::Assets;
-use bevy_ecs::{
-    query::Without,
-    system::{Query, Res},
-};
+#[cfg(feature = "bevy_text")]
+use bevy_ecs::query::Without;
+use bevy_ecs::system::{Query, Res};
 use bevy_math::Vec2;
 use bevy_render::texture::Image;
+#[cfg(feature = "bevy_text")]
 use bevy_text::Text;
 
 /// Updates calculated size of the node based on the image provided
 pub fn update_image_calculated_size_system(
     textures: Res<Assets<Image>>,
-    mut query: Query<(&mut CalculatedSize, &UiImage), Without<Text>>,
+    #[cfg(feature = "bevy_text")] mut query: Query<(&mut CalculatedSize, &UiImage), Without<Text>>,
+    #[cfg(not(feature = "bevy_text"))] mut query: Query<(&mut CalculatedSize, &UiImage)>,
 ) {
     for (mut calculated_size, image) in &mut query {
         if let Some(texture) = textures.get(&image.texture) {

crates/bevy_ui/src/widget/mod.rs

@@ -2,8 +2,10 @@
 
 mod button;
 mod image;
+#[cfg(feature = "bevy_text")]
 mod text;
 
 pub use button::*;
 pub use image::*;
+#[cfg(feature = "bevy_text")]
 pub use text::*;