src/tools/clippy/clippy_lints/src/partial_pub_fields.rs

   1 use clippy_utils::diagnostics::span_lint_and_help;
   2 use rustc_ast::ast::{Item, ItemKind};
   3 use rustc_lint::{EarlyContext, EarlyLintPass};
   4 use rustc_session::declare_lint_pass;
   5
   6 declare_clippy_lint! {
   7     /// ### What it does
   8     /// Checks whether partial fields of a struct are public.
   9     ///
  10     /// Either make all fields of a type public, or make none of them public
  11     ///
  12     /// ### Why is this bad?
  13     /// Most types should either be:
  14     /// * Abstract data types: complex objects with opaque implementation which guard
  15     /// interior invariants and expose intentionally limited API to the outside world.
  16     /// * Data: relatively simple objects which group a bunch of related attributes together.
  17     ///
  18     /// ### Example
  19     /// ```no_run
  20     /// pub struct Color {
  21     ///     pub r: u8,
  22     ///     pub g: u8,
  23     ///     b: u8,
  24     /// }
  25     /// ```
  26     /// Use instead:
  27     /// ```no_run
  28     /// pub struct Color {
  29     ///     pub r: u8,
  30     ///     pub g: u8,
  31     ///     pub b: u8,
  32     /// }
  33     /// ```
  34     #[clippy::version = "1.66.0"]
  35     pub PARTIAL_PUB_FIELDS,
  36     restriction,
  37     "partial fields of a struct are public"
  38 }
  39 declare_lint_pass!(PartialPubFields => [PARTIAL_PUB_FIELDS]);
  40
  41 impl EarlyLintPass for PartialPubFields {
  42     fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
  43         let ItemKind::Struct(ref st, _) = item.kind else {
  44             return;
  45         };
  46
  47         let mut fields = st.fields().iter();
  48         let Some(first_field) = fields.next() else {
  49             // Empty struct.
  50             return;
  51         };
  52         let all_pub = first_field.vis.kind.is_pub();
  53         let all_priv = !all_pub;
  54
  55         let msg = "mixed usage of pub and non-pub fields";
  56
  57         for field in fields {
  58             if all_priv && field.vis.kind.is_pub() {
  59                 span_lint_and_help(
  60                     cx,
  61                     PARTIAL_PUB_FIELDS,
  62                     field.vis.span,
  63                     msg,
  64                     None,
  65                     "consider using private field here",
  66                 );
  67                 return;
  68             } else if all_pub && !field.vis.kind.is_pub() {
  69                 span_lint_and_help(
  70                     cx,
  71                     PARTIAL_PUB_FIELDS,
  72                     field.vis.span,
  73                     msg,
  74                     None,
  75                     "consider using public field here",
  76                 );
  77                 return;
  78             }
  79         }
  80     }
  81 }