bevy_lint/lints/style/
plugin_not_ending_in_plugin.rs

1//! Checks for types who implement `Plugin` but whose names does not end in "Plugin".
2//!
3//! This does _not_ check function-style plugins (`fn plugin(app: &mut App)`), only structures with
4//! `Plugin` explicitly implemented with `impl Plugin for T`.
5//!
6//! # Motivation
7//!
8//! Unlike traits like [`Clone`] or [`Debug`], the primary purpose of a type that implements
9//! `Plugin` is to be a Bevy plugin. As such, it is common practice to suffix plugin names with
10//! "Plugin" to signal how they should be used.
11//!
12//! # Example
13//!
14//! ```
15//! # use bevy::prelude::*;
16//! #
17//! struct Physics;
18//!
19//! impl Plugin for Physics {
20//!     fn build(&self, app: &mut App) {
21//!         // ...
22//!     }
23//! }
24//! ```
25//!
26//! Use instead:
27//!
28//! ```
29//! # use bevy::prelude::*;
30//! #
31//! struct PhysicsPlugin;
32//!
33//! impl Plugin for PhysicsPlugin {
34//!     fn build(&self, app: &mut App) {
35//!         // ...
36//!     }
37//! }
38//! ```
39
40use crate::{declare_bevy_lint, declare_bevy_lint_pass};
41use clippy_utils::{diagnostics::span_lint_hir_and_then, match_def_path, path_res};
42use rustc_errors::Applicability;
43use rustc_hir::{HirId, Item, ItemKind, OwnerId, def::Res};
44use rustc_lint::{LateContext, LateLintPass};
45use rustc_span::symbol::Ident;
46
47declare_bevy_lint! {
48    pub PLUGIN_NOT_ENDING_IN_PLUGIN,
49    super::STYLE,
50    "implemented `Plugin` for a structure whose name does not end in \"Plugin\"",
51}
52
53declare_bevy_lint_pass! {
54    pub PluginNotEndingInPlugin => [PLUGIN_NOT_ENDING_IN_PLUGIN.lint],
55}
56
57impl<'tcx> LateLintPass<'tcx> for PluginNotEndingInPlugin {
58    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &Item<'tcx>) {
59        // Find `impl` items...
60        if let ItemKind::Impl(impl_) = item.kind
61            // ...that implement a trait...
62            && let Some(of_trait) = impl_.of_trait
63            // ...where the trait is a path to user code... (I don't believe this will ever be
64            // false, since the alternatives are primitives, `Self`, and others that wouldn't make
65            // since in this scenario.)
66            && let Res::Def(_, trait_def_id) = of_trait.path.res
67            // ...where the trait being implemented is Bevy's `Plugin`...
68            && match_def_path(cx, trait_def_id, &crate::paths::PLUGIN)
69        {
70            // Try to resolve where this type was originally defined. This will result in a `DefId`
71            // pointing to the original `struct Foo` definition, or `impl <T>` if it's a generic
72            // parameter.
73            let Some(struct_def_id) = path_res(cx, impl_.self_ty).opt_def_id() else {
74                return;
75            };
76
77            // If this type is a generic parameter, exit. Their names, such as `T`, cannot be
78            // referenced by others.
79            if impl_
80                .generics
81                .params
82                .iter()
83                .any(|param| param.def_id.to_def_id() == struct_def_id)
84            {
85                return;
86            }
87
88            // Find the original name and span of the type. (We don't use the name from the path,
89            // since that can be spoofed through `use Foo as FooPlugin`.)
90            let Some(Ident {
91                name: struct_name,
92                span: struct_span,
93            }) = cx.tcx.opt_item_ident(struct_def_id)
94            else {
95                return;
96            };
97
98            // skip lint if the struct was defined in an external macro
99            if struct_span.in_external_macro(cx.tcx.sess.source_map()) {
100                return;
101            }
102
103            // If the type's name ends in "Plugin", exit.
104            if struct_name.as_str().ends_with("Plugin") {
105                return;
106            }
107
108            // Convert the `DefId` of the structure to a `LocalDefId`. If it cannot be converted
109            // then the struct is from an external crate, in which case this lint should not be
110            // emitted. (The user cannot easily rename that struct if they didn't define it.)
111            let Some(struct_local_def_id) = struct_def_id.as_local() else {
112                return;
113            };
114
115            // Convert struct `LocalDefId` to an `HirId` so that we can emit the lint for the
116            // correct HIR node.
117            let struct_hir_id: HirId = OwnerId {
118                def_id: struct_local_def_id,
119            }
120            .into();
121
122            span_lint_hir_and_then(
123                cx,
124                PLUGIN_NOT_ENDING_IN_PLUGIN.lint,
125                struct_hir_id,
126                struct_span,
127                PLUGIN_NOT_ENDING_IN_PLUGIN.lint.desc,
128                |diag| {
129                    diag.span_suggestion(
130                        struct_span,
131                        "rename the plugin",
132                        format!("{struct_name}Plugin"),
133                        // There may be other references that also need to be renamed.
134                        Applicability::MaybeIncorrect,
135                    );
136
137                    diag.span_note(item.span, "`Plugin` implemented here");
138                },
139            );
140        }
141    }
142}
bevy_lint/lints/style/plugin_not_ending_in_plugin.rs

bevy_lint/lints/style/
plugin_not_ending_in_plugin.rs
