src/tools/clippy/clippy_lints/src/disallowed_script_idents.rs

   1 use clippy_utils::diagnostics::span_lint;
   2 use rustc_ast::ast;
   3 use rustc_data_structures::fx::FxHashSet;
   4 use rustc_lint::{EarlyContext, EarlyLintPass, Level};
   5 use rustc_session::{declare_tool_lint, impl_lint_pass};
   6 use unicode_script::{Script, UnicodeScript};
   7
   8 declare_clippy_lint! {
   9     /// ### What it does
  10     /// Checks for usage of unicode scripts other than those explicitly allowed
  11     /// by the lint config.
  12     ///
  13     /// This lint doesn't take into account non-text scripts such as `Unknown` and `Linear_A`.
  14     /// It also ignores the `Common` script type.
  15     /// While configuring, be sure to use official script name [aliases] from
  16     /// [the list of supported scripts][supported_scripts].
  17     ///
  18     /// See also: [`non_ascii_idents`].
  19     ///
  20     /// [aliases]: http://www.unicode.org/reports/tr24/tr24-31.html#Script_Value_Aliases
  21     /// [supported_scripts]: https://www.unicode.org/iso15924/iso15924-codes.html
  22     ///
  23     /// ### Why is this bad?
  24     /// It may be not desired to have many different scripts for
  25     /// identifiers in the codebase.
  26     ///
  27     /// Note that if you only want to allow plain English, you might want to use
  28     /// built-in [`non_ascii_idents`] lint instead.
  29     ///
  30     /// [`non_ascii_idents`]: https://doc.rust-lang.org/rustc/lints/listing/allowed-by-default.html#non-ascii-idents
  31     ///
  32     /// ### Example
  33     /// ```rust
  34     /// // Assuming that `clippy.toml` contains the following line:
  35     /// // allowed-locales = ["Latin", "Cyrillic"]
  36     /// let counter = 10; // OK, latin is allowed.
  37     /// let счётчик = 10; // OK, cyrillic is allowed.
  38     /// let zähler = 10; // OK, it's still latin.
  39     /// let カウンタ = 10; // Will spawn the lint.
  40     /// ```
  41     pub DISALLOWED_SCRIPT_IDENTS,
  42     restriction,
  43     "usage of non-allowed Unicode scripts"
  44 }
  45
  46 #[derive(Clone, Debug)]
  47 pub struct DisallowedScriptIdents {
  48     whitelist: FxHashSet<Script>,
  49 }
  50
  51 impl DisallowedScriptIdents {
  52     pub fn new(whitelist: &[String]) -> Self {
  53         let whitelist = whitelist
  54             .iter()
  55             .map(String::as_str)
  56             .filter_map(Script::from_full_name)
  57             .collect();
  58         Self { whitelist }
  59     }
  60 }
  61
  62 impl_lint_pass!(DisallowedScriptIdents => [DISALLOWED_SCRIPT_IDENTS]);
  63
  64 impl EarlyLintPass for DisallowedScriptIdents {
  65     fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
  66         // Implementation is heavily inspired by the implementation of [`non_ascii_idents`] lint:
  67         // https://github.com/rust-lang/rust/blob/master/compiler/rustc_lint/src/non_ascii_idents.rs
  68
  69         let check_disallowed_script_idents = cx.builder.lint_level(DISALLOWED_SCRIPT_IDENTS).0 != Level::Allow;
  70         if !check_disallowed_script_idents {
  71             return;
  72         }
  73
  74         let symbols = cx.sess.parse_sess.symbol_gallery.symbols.lock();
  75         // Sort by `Span` so that error messages make sense with respect to the
  76         // order of identifier locations in the code.
  77         let mut symbols: Vec<_> = symbols.iter().collect();
  78         symbols.sort_unstable_by_key(|k| k.1);
  79
  80         for (symbol, &span) in &symbols {
  81             // Note: `symbol.as_str()` is an expensive operation, thus should not be called
  82             // more than once for a single symbol.
  83             let symbol_str = symbol.as_str();
  84             if symbol_str.is_ascii() {
  85                 continue;
  86             }
  87
  88             for c in symbol_str.chars() {
  89                 // We want to iterate through all the scripts associated with this character
  90                 // and check whether at least of one scripts is in the whitelist.
  91                 let forbidden_script = c
  92                     .script_extension()
  93                     .iter()
  94                     .find(|script| !self.whitelist.contains(script));
  95                 if let Some(script) = forbidden_script {
  96                     span_lint(
  97                         cx,
  98                         DISALLOWED_SCRIPT_IDENTS,
  99                         span,
 100                         &format!(
 101                             "identifier `{}` has a Unicode script that is not allowed by configuration: {}",
 102                             symbol_str,
 103                             script.full_name()
 104                         ),
 105                     );
 106                     // We don't want to spawn warning multiple times over a single identifier.
 107                     break;
 108                 }
 109             }
 110         }
 111     }
 112 }