lint: Res<Events<T>>

bevy_lint/src/lints/mod.rs

@@ -14,6 +14,7 @@ pub mod main_return_without_appexit;
 pub mod missing_reflect;
 pub mod panicking_methods;
 pub mod plugin_not_ending_in_plugin;
+pub mod sus_resource;
 pub mod zst_query;
 
 pub(crate) static LINTS: &[&BevyLint] = &[
@@ -26,6 +27,7 @@ pub(crate) static LINTS: &[&BevyLint] = &[
     panicking_methods::PANICKING_WORLD_METHODS,
     plugin_not_ending_in_plugin::PLUGIN_NOT_ENDING_IN_PLUGIN,
     zst_query::ZST_QUERY,
+    sus_resource::EVENTS_RESOURCE_SYSTEM_PARAM,
 ];
 
 pub(crate) fn register_lints(store: &mut LintStore) {
@@ -46,4 +48,6 @@ pub(crate) fn register_passes(store: &mut LintStore) {
     });
     store.register_late_pass(|_| Box::new(zst_query::ZstQuery::default()));
     store.register_late_pass(|_| Box::new(insert_unit_bundle::InsertUnitBundle::default()));
+
+    store.register_late_pass(|_| Box::new(sus_resource::EventsResourceSystemParam::default()));
 }

bevy_lint/src/lints/sus_resource.rs

@@ -0,0 +1,72 @@
+use crate::{
+    declare_bevy_lint, declare_bevy_lint_pass,
+    utils::hir_parse::{detuple, generic_type_at},
+};
+use clippy_utils::{
+    diagnostics::span_lint_and_help,
+    ty::match_type,
+};
+use rustc_hir_analysis::collect::ItemCtxt;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty::Ty;
+
+declare_bevy_lint! {
+    pub EVENTS_RESOURCE_SYSTEM_PARAM,
+    RESTRICTION,
+    // FIXME: Better note.
+    "use of bad system parameter",
+}
+
+declare_bevy_lint_pass! {
+    pub EventsResourceSystemParam => [EVENTS_RESOURCE_SYSTEM_PARAM.lint],
+}
+
+impl<'tcx> LateLintPass<'tcx> for EventsResourceSystemParam {
+    fn check_ty(&mut self, cx: &LateContext<'tcx>, hir_ty: &'tcx rustc_hir::Ty<'tcx>) {
+        let item_cx = ItemCtxt::new(cx.tcx, hir_ty.hir_id.owner.def_id);
+        let ty = item_cx.lower_ty(hir_ty);
+
+        let Some(res_kind) = ResKind::try_from_ty(cx, ty) else {
+            return;
+        };
+
+        let Some(res_data_ty) = generic_type_at(cx, hir_ty, 1) else {
+            return;
+        };
+
+        // FIXME: Is detuple necessary ? Or will `T` in `Res<T>` always be a single type ?
+        detuple(*res_data_ty)
+            .iter()
+            .filter(|&hir_ty| match_type(cx, item_cx.lower_ty(hir_ty), &crate::paths::EVENTS))
+            .for_each(|hir_ty| {
+                span_lint_and_help(
+                    cx,
+                    EVENTS_RESOURCE_SYSTEM_PARAM.lint,
+                    hir_ty.span,
+                    EVENTS_RESOURCE_SYSTEM_PARAM.lint.desc,
+                    None,
+                    res_kind.help(None),
+                )
+            });
+    }
+}
+
+enum ResKind {
+    Res,
+}
+
+impl ResKind {
+    fn try_from_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Self> {
+        if match_type(cx, ty, &crate::paths::RES) {
+            Some(Self::Res)
+        } else {
+            None
+        }
+    }
+
+    fn help(&self, o_ty: Option<&Ty<'_>>) -> String {
+        match self {
+            Self::Res => format!("events Resource footgun"),
+        }
+    }
+}

bevy_lint/src/paths.rs

@@ -24,6 +24,7 @@ pub const PTR_MUT: [&str; 2] = ["bevy_ptr", "PtrMut"];
 pub const QUERY: [&str; 4] = ["bevy_ecs", "system", "query", "Query"];
 pub const QUERY_STATE: [&str; 4] = ["bevy_ecs", "query", "state", "QueryState"];
 pub const REFLECT: [&str; 3] = ["bevy_reflect", "reflect", "Reflect"];
+pub const RES: [&str; 3] = ["bevy_ecs", "change_detection", "Res"];
 pub const RES_MUT: [&str; 3] = ["bevy_ecs", "change_detection", "ResMut"];
 pub const RESOURCE: [&str; 4] = ["bevy_ecs", "system", "system_param", "Resource"];
 pub const WORLD: [&str; 3] = ["bevy_ecs", "world", "World"];

bevy_lint/tests/ui/sus_resource/my_test.rs

@@ -0,0 +1,13 @@
+#![feature(register_tool)]
+#![register_tool(bevy)]
+#![deny(bevy::events_resource_system_param)]
+
+use bevy::prelude::*;
+
+fn main() {
+    App::new().add_systems(Startup, (bad_system,)).run();
+}
+
+//~| HELP: events Resource footgun
+//~v ERROR: use of bad system parameter
+fn bad_system(_resource_events: Res<Events<AppExit>>) {}

bevy_lint/tests/ui/sus_resource/my_test.stderr

@@ -0,0 +1,15 @@
+error: use of bad system parameter
+  --> tests/ui/sus_resource/my_test.rs:13:37
+   |
+13 | fn bad_system(_resource_events: Res<Events<AppExit>>) {}
+   |                                     ^^^^^^^^^^^^^^^
+   |
+   = help: events Resource footgun
+note: the lint level is defined here
+  --> tests/ui/sus_resource/my_test.rs:3:9
+   |
+3  | #![deny(bevy::events_resource_system_param)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+