refactor: Generate Linter -> RuleSelector mapping via macro

To enable ruff_dev to automatically generate the rule Markdown tables in
the README the ruff library contained the following function:

    Linter::codes() -> Vec<RuleSelector>

which was slightly changed to `fn prefixes(&self) -> Prefixes` in
9dc66b5a65 to enable ruff_dev to split
up the Markdown tables for linters that have multiple prefixes
(pycodestyle has E & W, Pylint has PLC, PLE, PLR & PLW).

The definition of this method was however largely redundant with the
#[prefix] macro attributes in the Linter enum, which are used to
derive the Linter::parse_code function, used by the --explain command.

This commit removes the redundant Linter::prefixes by introducing a
same-named method with a different signature to the RuleNamespace trait:

     fn prefixes(&self) -> &'static [&'static str];

As well as implementing IntoIterator<Rule> for &Linter. We extend the
extisting RuleNamespace proc macro to automatically derive both
implementations from the Linter enum definition.

To support the previously mentioned Markdown table splitting we
introduce a very simple hand-written method to the Linter impl:

    fn categories(&self) -> Option<&'static [LinterCategory]>;

README.md

@@ -134,7 +134,7 @@ developer of [Zulip](https://github.com/zulip/zulip):
    1. [eradicate (ERA)](#eradicate-era)
    1. [pandas-vet (PD)](#pandas-vet-pd)
    1. [pygrep-hooks (PGH)](#pygrep-hooks-pgh)
-   1. [Pylint (PLC, PLE, PLR, PLW)](#pylint-plc-ple-plr-plw)
+   1. [Pylint (PL)](#pylint-pl)
    1. [flake8-pie (PIE)](#flake8-pie-pie)
    1. [flake8-commas (COM)](#flake8-commas-com)
    1. [flake8-no-pep420 (INP)](#flake8-no-pep420-inp)
@@ -1108,7 +1108,7 @@ For more, see [pygrep-hooks](https://github.com/pre-commit/pygrep-hooks) on GitH
 | PGH003 | blanket-type-ignore | Use specific rule codes when ignoring type issues |  |
 | PGH004 | blanket-noqa | Use specific rule codes when using `noqa` |  |
 
-### Pylint (PLC, PLE, PLR, PLW)
+### Pylint (PL)
 
 For more, see [Pylint](https://pypi.org/project/pylint/2.15.7/) on PyPI.
 

ruff_cli/tests/black_compatibility_test.rs

@@ -13,7 +13,7 @@ use assert_cmd::Command;
 use itertools::Itertools;
 use log::info;
 use ruff::logging::{set_up_logging, LogLevel};
-use ruff::registry::Linter;
+use ruff::registry::{Linter, RuleNamespace};
 use strum::IntoEnumIterator;
 use walkdir::WalkDir;
 
@@ -180,7 +180,7 @@ fn test_ruff_black_compatibility() -> Result<()> {
         // problem. Ruff would add a `# noqa: W292`  after the first run, black introduces a
         // newline, and ruff removes the `# noqa: W292` again.
         .filter(|linter| *linter != Linter::Ruff)
-        .map(|linter| linter.prefixes().as_list(","))
+        .map(|linter| linter.prefixes().join(","))
         .join(",");
     let ruff_args = [
         "-",

ruff_dev/src/generate_rules_table.rs

@@ -2,7 +2,7 @@
 
 use anyhow::Result;
 use clap::Args;
-use ruff::registry::{Linter, Prefixes, RuleSelector};
+use ruff::registry::{Linter, LinterCategory, Rule, RuleNamespace};
 use strum::IntoEnumIterator;
 
 use crate::utils::replace_readme_section;
@@ -20,12 +20,12 @@ pub struct Cli {
     pub(crate) dry_run: bool,
 }
 
-fn generate_table(table_out: &mut String, selector: &RuleSelector) {
+fn generate_table(table_out: &mut String, rules: impl IntoIterator<Item = Rule>) {
     table_out.push_str("| Code | Name | Message | Fix |");
     table_out.push('\n');
     table_out.push_str("| ---- | ---- | ------- | --- |");
     table_out.push('\n');
-    for rule in selector {
+    for rule in rules {
         let fix_token = match rule.autofixable() {
             None => "",
             Some(_) => "🛠",
@@ -48,8 +48,7 @@ pub fn main(cli: &Cli) -> Result<()> {
     let mut table_out = String::new();
     let mut toc_out = String::new();
     for linter in Linter::iter() {
-        let prefixes = linter.prefixes();
+        let codes_csv: String = linter.prefixes().join(", ");
-        let codes_csv: String = prefixes.as_list(", ");
         table_out.push_str(&format!("### {} ({codes_csv})", linter.name()));
         table_out.push('\n');
         table_out.push('\n');
@@ -86,15 +85,14 @@ pub fn main(cli: &Cli) -> Result<()> {
             table_out.push('\n');
         }
 
-        match prefixes {
+        if let Some(categories) = linter.categories() {
-            Prefixes::Single(prefix) => generate_table(&mut table_out, &prefix),
+            for LinterCategory(prefix, name, selector) in categories {
-            Prefixes::Multiple(entries) => {
+                table_out.push_str(&format!("#### {name} ({prefix})"));
-                for (selector, category) in entries {
-                    table_out.push_str(&format!("#### {category} ({})", selector.as_ref()));
                 table_out.push('\n');
-                    generate_table(&mut table_out, &selector);
+                generate_table(&mut table_out, selector);
-                }
             }
+        } else {
+            generate_table(&mut table_out, &linter);
         }
     }
 

ruff_macros/src/rule_namespace.rs

@@ -1,3 +1,4 @@
+use proc_macro2::{Ident, Span};
 use quote::quote;
 use syn::spanned::Spanned;
 use syn::{Data, DataEnum, DeriveInput, Error, Lit, Meta, MetaNameValue};
@@ -11,6 +12,8 @@ pub fn derive_impl(input: DeriveInput) -> syn::Result<proc_macro2::TokenStream>
 
     let mut parsed = Vec::new();
 
+    let mut prefix_match_arms = quote!();
+
     for variant in variants {
         let prefix_attrs: Vec<_> = variant
             .attrs
@@ -25,23 +28,48 @@ pub fn derive_impl(input: DeriveInput) -> syn::Result<proc_macro2::TokenStream>
             ));
         }
 
+        let mut prefix_literals = Vec::new();
+
         for attr in prefix_attrs {
             let Ok(Meta::NameValue(MetaNameValue{lit: Lit::Str(lit), ..})) = attr.parse_meta() else {
                 return Err(Error::new(attr.span(), r#"expected attribute to be in the form of [#prefix = "..."]"#))
             };
-            parsed.push((lit, variant.ident.clone()));
+            parsed.push((lit.clone(), variant.ident.clone()));
+            prefix_literals.push(lit);
         }
+
+        let variant_ident = variant.ident;
+
+        prefix_match_arms.extend(quote! {
+            Self::#variant_ident => &[#(#prefix_literals),*],
+        });
     }
 
     parsed.sort_by_key(|(prefix, _)| prefix.value().len());
 
     let mut if_statements = quote!();
+    let mut into_iter_match_arms = quote!();
 
     for (prefix, field) in parsed {
         if_statements.extend(quote! {if let Some(rest) = code.strip_prefix(#prefix) {
             return Some((#ident::#field, rest));
         }});
+
+        let prefix_ident = Ident::new(&prefix.value(), Span::call_site());
+
+        if field != "Pycodestyle" {
+            into_iter_match_arms.extend(quote! {
+                #ident::#field => RuleSelector::#prefix_ident.into_iter(),
+            });
         }
+    }
+
+    into_iter_match_arms.extend(quote! {
+        #ident::Pycodestyle => {
+            let rules: Vec<_> = (&RuleSelector::E).into_iter().chain(&RuleSelector::W).collect();
+            rules.into_iter()
+        }
+    });
 
     Ok(quote! {
         impl crate::registry::RuleNamespace for #ident {
@@ -49,6 +77,24 @@ pub fn derive_impl(input: DeriveInput) -> syn::Result<proc_macro2::TokenStream>
                 #if_statements
                 None
             }
+
+
+            fn prefixes(&self) -> &'static [&'static str] {
+                match self { #prefix_match_arms }
+            }
+        }
+
+        impl IntoIterator for &#ident {
+            type Item = Rule;
+            type IntoIter = ::std::vec::IntoIter<Self::Item>;
+
+            fn into_iter(self) -> Self::IntoIter {
+                use colored::Colorize;
+
+                match self {
+                    #into_iter_match_arms
+                }
+            }
         }
     })
 }

scripts/add_plugin.py

@@ -89,12 +89,6 @@ mod tests {
                 fp.write(f"{indent}{pascal_case(plugin)},")
                 fp.write("\n")
 
-            elif line.strip() == "Linter::Ruff => Prefixes::Single(RuleSelector::RUF),":
-                fp.write(
-                    f"{indent}Linter::{pascal_case(plugin)} => Prefixes::Single(RuleSelector::{prefix_code}),"
-                )
-                fp.write("\n")
-
             fp.write(line)
             fp.write("\n")
 

src/registry.rs

@@ -1,6 +1,5 @@
 //! Registry of [`Rule`] to [`DiagnosticKind`] mappings.
 
-use itertools::Itertools;
 use once_cell::sync::Lazy;
 use ruff_macros::RuleNamespace;
 use rustc_hash::FxHashMap;
@@ -446,7 +445,7 @@ pub enum Linter {
     #[prefix = "E"]
     #[prefix = "W"]
     Pycodestyle,
-    #[prefix = "C9"]
+    #[prefix = "C90"]
     McCabe,
     #[prefix = "I"]
     Isort,
@@ -522,76 +521,29 @@ pub enum Linter {
 
 pub trait RuleNamespace: Sized {
     fn parse_code(code: &str) -> Option<(Self, &str)>;
-}
 
-pub enum Prefixes {
+    fn prefixes(&self) -> &'static [&'static str];
-    Single(RuleSelector),
-    Multiple(Vec<(RuleSelector, &'static str)>),
-}
-
-impl Prefixes {
-    pub fn as_list(&self, separator: &str) -> String {
-        match self {
-            Prefixes::Single(prefix) => prefix.as_ref().to_string(),
-            Prefixes::Multiple(entries) => entries
-                .iter()
-                .map(|(prefix, _)| prefix.as_ref())
-                .join(separator),
-        }
-    }
 }
 
 include!(concat!(env!("OUT_DIR"), "/linter.rs"));
 
+/// The prefix, name and selector for an upstream linter category.
+pub struct LinterCategory(pub &'static str, pub &'static str, pub RuleSelector);
+
 impl Linter {
-    pub fn prefixes(&self) -> Prefixes {
+    pub fn categories(&self) -> Option<&'static [LinterCategory]> {
         match self {
-            Linter::Eradicate => Prefixes::Single(RuleSelector::ERA),
+            Linter::Pycodestyle => Some(&[
-            Linter::Flake82020 => Prefixes::Single(RuleSelector::YTT),
+                LinterCategory("E", "Error", RuleSelector::E),
-            Linter::Flake8Annotations => Prefixes::Single(RuleSelector::ANN),
+                LinterCategory("W", "Warning", RuleSelector::W),
-            Linter::Flake8Bandit => Prefixes::Single(RuleSelector::S),
-            Linter::Flake8BlindExcept => Prefixes::Single(RuleSelector::BLE),
-            Linter::Flake8BooleanTrap => Prefixes::Single(RuleSelector::FBT),
-            Linter::Flake8Bugbear => Prefixes::Single(RuleSelector::B),
-            Linter::Flake8Builtins => Prefixes::Single(RuleSelector::A),
-            Linter::Flake8Comprehensions => Prefixes::Single(RuleSelector::C4),
-            Linter::Flake8Datetimez => Prefixes::Single(RuleSelector::DTZ),
-            Linter::Flake8Debugger => Prefixes::Single(RuleSelector::T10),
-            Linter::Flake8ErrMsg => Prefixes::Single(RuleSelector::EM),
-            Linter::Flake8ImplicitStrConcat => Prefixes::Single(RuleSelector::ISC),
-            Linter::Flake8ImportConventions => Prefixes::Single(RuleSelector::ICN),
-            Linter::Flake8Print => Prefixes::Single(RuleSelector::T20),
-            Linter::Flake8PytestStyle => Prefixes::Single(RuleSelector::PT),
-            Linter::Flake8Quotes => Prefixes::Single(RuleSelector::Q),
-            Linter::Flake8Return => Prefixes::Single(RuleSelector::RET),
-            Linter::Flake8Simplify => Prefixes::Single(RuleSelector::SIM),
-            Linter::Flake8TidyImports => Prefixes::Single(RuleSelector::TID),
-            Linter::Flake8UnusedArguments => Prefixes::Single(RuleSelector::ARG),
-            Linter::Isort => Prefixes::Single(RuleSelector::I),
-            Linter::McCabe => Prefixes::Single(RuleSelector::C90),
-            Linter::PEP8Naming => Prefixes::Single(RuleSelector::N),
-            Linter::PandasVet => Prefixes::Single(RuleSelector::PD),
-            Linter::Pycodestyle => Prefixes::Multiple(vec![
-                (RuleSelector::E, "Error"),
-                (RuleSelector::W, "Warning"),
             ]),
-            Linter::Pydocstyle => Prefixes::Single(RuleSelector::D),
+            Linter::Pylint => Some(&[
-            Linter::Pyflakes => Prefixes::Single(RuleSelector::F),
+                LinterCategory("PLC", "Convention", RuleSelector::PLC),
-            Linter::PygrepHooks => Prefixes::Single(RuleSelector::PGH),
+                LinterCategory("PLE", "Error", RuleSelector::PLE),
-            Linter::Pylint => Prefixes::Multiple(vec![
+                LinterCategory("PLR", "Refactor", RuleSelector::PLR),
-                (RuleSelector::PLC, "Convention"),
+                LinterCategory("PLW", "Warning", RuleSelector::PLW),
-                (RuleSelector::PLE, "Error"),
-                (RuleSelector::PLR, "Refactor"),
-                (RuleSelector::PLW, "Warning"),
             ]),
-            Linter::Pyupgrade => Prefixes::Single(RuleSelector::UP),
+            _ => None,
-            Linter::Flake8Pie => Prefixes::Single(RuleSelector::PIE),
-            Linter::Flake8Commas => Prefixes::Single(RuleSelector::COM),
-            Linter::Flake8NoPep420 => Prefixes::Single(RuleSelector::INP),
-            Linter::Flake8Executable => Prefixes::Single(RuleSelector::EXE),
-            Linter::Flake8TypeChecking => Prefixes::Single(RuleSelector::TYP),
-            Linter::Tryceratops => Prefixes::Single(RuleSelector::TRY),
-            Linter::Ruff => Prefixes::Single(RuleSelector::RUF),
         }
     }
 }