Add UI tests for existing lints (#128)

Part of #31.

This is a continuation of #125 that actually adds UI tests for all of
the current lints. It was split off to make #125 easier to review.

To test this, run:

```bash
cargo test -p bevy_lint --test ui
```

To bless changes, run:

```bash
cargo test -p bevy_lint --test ui -- --bless
```

There are a few additional options available if you replace `--bless`
with `--help`, too.

bevy_lint/src/lints/main_return_without_appexit.rs

@@ -9,6 +9,11 @@
 //! it from `main()` will set the exit code, which allows external processes to detect whether there
 //! was an error.
 //!
+//! # Known issues
+//!
+//! If you wish to silence this lint, you must add `#[allow(bevy::main_return_without_appexit)]` to
+//! `fn main()`, not the line that calls `App::run()`.
+//!
 //! # Example
 //!
 //! ```

bevy_lint/tests/ui/insert_event_resource/bug_94.rs

@@ -0,0 +1,22 @@
+//! This test tracks the bug reported in [#94]. When this starts failing, the bug has been fixed.
+//!
+//! [#94]: https://github.com/TheBevyFlock/bevy_cli/issues/94
+
+//@check-pass
+
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::insert_event_resource)]
+
+use bevy::prelude::*;
+
+#[derive(Event)]
+struct Foo;
+
+fn main() {
+    let mut app = App::new();
+
+    // These both should error, but currently do not.
+    App::init_resource::<Events<Foo>>(&mut app);
+    App::insert_resource::<Events<Foo>>(&mut app, Default::default());
+}

bevy_lint/tests/ui/insert_event_resource/main.fixed

@@ -0,0 +1,26 @@
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::insert_event_resource)]
+
+use bevy::prelude::*;
+
+#[derive(Event)]
+struct Foo;
+
+fn main() {
+    App::new().add_event::<Foo>();
+    //~^ ERROR: called `App::init_resource::<Events<T>>()` instead of `App::add_event::<T>()`
+
+    App::new().add_event::<Foo>();
+    //~^ ERROR: called `App::insert_resource(Events<T>)` instead of `App::add_event::<T>()`
+
+    // Make sure the correct type is detected, even when not explicitly passed to
+    // `insert_resource()`.
+    let implied_event: Events<Foo> = Default::default();
+    App::new().add_event::<Foo>();
+    //~^ ERROR: called `App::insert_resource(Events<T>)` instead of `App::add_event::<T>()`
+
+    // Ensure the lint can be muted by annotating the expression.
+    #[allow(bevy::insert_event_resource)]
+    App::new().init_resource::<Events<Foo>>();
+}

bevy_lint/tests/ui/insert_event_resource/main.rs

@@ -0,0 +1,26 @@
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::insert_event_resource)]
+
+use bevy::prelude::*;
+
+#[derive(Event)]
+struct Foo;
+
+fn main() {
+    App::new().init_resource::<Events<Foo>>();
+    //~^ ERROR: called `App::init_resource::<Events<T>>()` instead of `App::add_event::<T>()`
+
+    App::new().insert_resource::<Events<Foo>>(Default::default());
+    //~^ ERROR: called `App::insert_resource(Events<T>)` instead of `App::add_event::<T>()`
+
+    // Make sure the correct type is detected, even when not explicitly passed to
+    // `insert_resource()`.
+    let implied_event: Events<Foo> = Default::default();
+    App::new().insert_resource(implied_event);
+    //~^ ERROR: called `App::insert_resource(Events<T>)` instead of `App::add_event::<T>()`
+
+    // Ensure the lint can be muted by annotating the expression.
+    #[allow(bevy::insert_event_resource)]
+    App::new().init_resource::<Events<Foo>>();
+}

bevy_lint/tests/ui/insert_event_resource/main.stderr

@@ -0,0 +1,40 @@
+error: called `App::init_resource::<Events<T>>()` instead of `App::add_event::<T>()`
+  --> tests/ui/insert_event_resource/main.rs:11:16
+   |
+11 |     App::new().init_resource::<Events<Foo>>();
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> tests/ui/insert_event_resource/main.rs:3:9
+   |
+3  | #![deny(bevy::insert_event_resource)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: inserting an `Events` resource does not fully setup that event
+   |
+11 |     App::new().add_event::<Foo>();
+   |                ~~~~~~~~~~~~~~~~~~
+
+error: called `App::insert_resource(Events<T>)` instead of `App::add_event::<T>()`
+  --> tests/ui/insert_event_resource/main.rs:14:16
+   |
+14 |     App::new().insert_resource::<Events<Foo>>(Default::default());
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: inserting an `Events` resource does not fully setup that event
+   |
+14 |     App::new().add_event::<Foo>();
+   |                ~~~~~~~~~~~~~~~~~~
+
+error: called `App::insert_resource(Events<T>)` instead of `App::add_event::<T>()`
+  --> tests/ui/insert_event_resource/main.rs:20:16
+   |
+20 |     App::new().insert_resource(implied_event);
+   |                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: inserting an `Events` resource does not fully setup that event
+   |
+20 |     App::new().add_event::<Foo>();
+   |                ~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 3 previous errors
+

bevy_lint/tests/ui/main_return_without_appexit/bug_132.rs

@@ -0,0 +1,20 @@
+//! A version of `main.rs` where the lint is muted on the expression. Since this lint is run on
+//! functions, it will still error.
+//!
+//! This test tracks the bug reported in [#132]. When this starts failing, the bug has been fixed.
+//!
+//! [#132]: https://github.com/TheBevyFlock/bevy_cli/issues/132
+
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::main_return_without_appexit)]
+
+use bevy::prelude::*;
+
+fn main() {
+    //~^ HELP: try
+
+    #[allow(bevy::main_return_without_appexit)]
+    App::new().run();
+    //~^ ERROR: an entrypoint that calls `App::run()` does not return `AppExit`
+}

bevy_lint/tests/ui/main_return_without_appexit/bug_132.stderr

@@ -0,0 +1,18 @@
+error: an entrypoint that calls `App::run()` does not return `AppExit`
+  --> tests/ui/main_return_without_appexit/bug_132.rs:18:16
+   |
+14 | fn main() {
+   |          - help: try: `-> AppExit`
+...
+18 |     App::new().run();
+   |                ^^^^^
+   |
+   = note: `App::run()` returns `AppExit`, which can be used to determine whether the app exited successfully or not
+note: the lint level is defined here
+  --> tests/ui/main_return_without_appexit/bug_132.rs:10:9
+   |
+10 | #![deny(bevy::main_return_without_appexit)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

bevy_lint/tests/ui/main_return_without_appexit/bug_87.rs

@@ -0,0 +1,17 @@
+//! This test tracks the bug reported in [#87]. When this starts failing, the bug has been fixed.
+//!
+//! [#87]: https://github.com/TheBevyFlock/bevy_cli/issues/87
+
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::main_return_without_appexit)]
+
+use bevy::prelude::*;
+
+fn main() {
+    // This should not raise an error, since `AppExit` is not ignored.
+    let app_exit = App::new().run();
+    //~^ ERROR: an entrypoint that calls `App::run()` does not return `AppExit`
+
+    println!("{app_exit:?}");
+}

bevy_lint/tests/ui/main_return_without_appexit/bug_87.stderr

@@ -0,0 +1,18 @@
+error: an entrypoint that calls `App::run()` does not return `AppExit`
+  --> tests/ui/main_return_without_appexit/bug_87.rs:13:31
+   |
+11 | fn main() {
+   |          - help: try: `-> AppExit`
+12 |     // This should not raise an error, since `AppExit` is not ignored.
+13 |     let app_exit = App::new().run();
+   |                               ^^^^^
+   |
+   = note: `App::run()` returns `AppExit`, which can be used to determine whether the app exited successfully or not
+note: the lint level is defined here
+  --> tests/ui/main_return_without_appexit/bug_87.rs:7:9
+   |
+7  | #![deny(bevy::main_return_without_appexit)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

bevy_lint/tests/ui/main_return_without_appexit/bug_94.rs

@@ -0,0 +1,18 @@
+//! This test tracks the bug reported in [#94]. When this starts failing, the bug has been fixed.
+//!
+//! [#94]: https://github.com/TheBevyFlock/bevy_cli/issues/94
+
+//@check-pass
+
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::main_return_without_appexit)]
+
+use bevy::prelude::*;
+
+fn main() {
+    let mut app = App::new();
+
+    // This should error because the `AppExit` is not handled, but it does not.
+    App::run(&mut app);
+}

bevy_lint/tests/ui/main_return_without_appexit/main.rs

@@ -0,0 +1,13 @@
+//! Tests the most basic version: where `main()` returns nothing and `AppExit` is not handled.
+
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::main_return_without_appexit)]
+
+use bevy::prelude::*;
+
+fn main() {
+    //~^ HELP: try
+    App::new().run();
+    //~^ ERROR: an entrypoint that calls `App::run()` does not return `AppExit`
+}

bevy_lint/tests/ui/main_return_without_appexit/main.stderr

@@ -0,0 +1,18 @@
+error: an entrypoint that calls `App::run()` does not return `AppExit`
+  --> tests/ui/main_return_without_appexit/main.rs:11:16
+   |
+9  | fn main() {
+   |          - help: try: `-> AppExit`
+10 |
+11 |     App::new().run();
+   |                ^^^^^
+   |
+   = note: `App::run()` returns `AppExit`, which can be used to determine whether the app exited successfully or not
+note: the lint level is defined here
+  --> tests/ui/main_return_without_appexit/main.rs:5:9
+   |
+5  | #![deny(bevy::main_return_without_appexit)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

bevy_lint/tests/ui/main_return_without_appexit/muted_function.rs

@@ -0,0 +1,15 @@
+//! A version of `main.rs` where the lint is muted on the function. This should pass without any
+//! errors.
+
+//@check-pass
+
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::main_return_without_appexit)]
+
+use bevy::prelude::*;
+
+#[allow(bevy::main_return_without_appexit)]
+fn main() {
+    App::new().run();
+}

bevy_lint/tests/ui/main_return_without_appexit/return_appexit.rs

@@ -0,0 +1,14 @@
+//! Tests when `main()` returns `AppExit`, meaning the user has fixed the lint. No diagnostics
+//! should be emitted in this case.
+
+//@check-pass
+
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::main_return_without_appexit)]
+
+use bevy::prelude::*;
+
+fn main() -> AppExit {
+    App::new().run()
+}

bevy_lint/tests/ui/main_return_without_appexit/return_result.rs

@@ -0,0 +1,16 @@
+//! Tests when `main()` returns a type other than the unit `()`. When this is done no lint is
+//! emitted, since we assume the user knows what they're doing.
+
+//@check-pass
+
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::main_return_without_appexit)]
+
+use bevy::prelude::*;
+
+fn main() -> Result<(), ()> {
+    App::new().run();
+
+    Ok(())
+}

bevy_lint/tests/ui/main_return_without_appexit.rs → bevy_lint/tests/ui/main_return_without_appexit/return_unit.rs

@@ -4,7 +4,8 @@
 
 use bevy::prelude::*;
 
-fn main() {
+fn main() -> () {
+    //~^ HELP: try
     App::new().run();
     //~^ ERROR: an entrypoint that calls `App::run()` does not return `AppExit`
 }

bevy_lint/tests/ui/main_return_without_appexit.stderr → bevy_lint/tests/ui/main_return_without_appexit/return_unit.stderr

@@ -1,14 +1,15 @@
 error: an entrypoint that calls `App::run()` does not return `AppExit`
- --> tests/ui/main_return_without_appexit.rs:8:16
+ --> tests/ui/main_return_without_appexit/return_unit.rs:9:16
   |
-7 | fn main() {
-  |          - help: try: `-> AppExit`
-8 |     App::new().run();
+7 | fn main() -> () {
+  |              -- help: try: `AppExit`
+8 |
+9 |     App::new().run();
   |                ^^^^^
   |
   = note: `App::run()` returns `AppExit`, which can be used to determine whether the app exited successfully or not
 note: the lint level is defined here
- --> tests/ui/main_return_without_appexit.rs:3:9
+ --> tests/ui/main_return_without_appexit/return_unit.rs:3:9
   |
 3 | #![deny(bevy::main_return_without_appexit)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

bevy_lint/tests/ui/panicking_methods/query.rs

@@ -0,0 +1,34 @@
+//! This tests the `panicking_query_methods` lint, specifically when triggered on the `Query` type.
+
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::panicking_query_methods)]
+
+use bevy::prelude::*;
+
+#[derive(Component)]
+struct Foo;
+
+fn main() {
+    App::new().add_systems(Startup, my_system);
+}
+
+fn my_system(mut query: Query<&mut Foo>) {
+    query.single();
+    //~^ ERROR:  called a `Query` method that can panic when a non-panicking alternative exists
+    //~| HELP: use `query.get_single()`
+
+    query.single_mut();
+    //~^ ERROR:  called a `Query` method that can panic when a non-panicking alternative exists
+    //~| HELP: use `query.get_single_mut()`
+
+    let entities = [Entity::PLACEHOLDER; 3];
+
+    let [_, _, _] = query.many(entities);
+    //~^ ERROR:  called a `Query` method that can panic when a non-panicking alternative exists
+    //~| HELP: use `query.get_many(entities)`
+
+    query.many_mut([]);
+    //~^ ERROR:  called a `Query` method that can panic when a non-panicking alternative exists
+    //~| HELP: use `query.get_many_mut([])`
+}