Allow rules without codes

CONTRIBUTING.md

@@ -120,12 +120,13 @@ after running `cargo test` like so:
 cargo insta review
 ```
 
-If your pull request relates to a specific lint rule, include the category and rule code in the
-title, as in the following examples:
+If your pull request relates to a specific lint rule, include the category and rule code or name in
+the title, as in the following examples:
 
 - \[`flake8-bugbear`\] Avoid false positive for usage after `continue` (`B031`)
 - \[`flake8-simplify`\] Detect implicit `else` cases in `needless-bool` (`SIM103`)
 - \[`pycodestyle`\] Implement `redundant-backslash` (`E502`)
+- \[`pedantic`\] Implement `pytest-fixture-autouse`
 
 Your pull request will be reviewed by a maintainer, which may involve a few rounds of iteration
 prior to merging.
@@ -225,7 +226,17 @@ adding a new lint rule are as follows:
     statements, like imports) or `analyze/expression.rs` (if your rule is based on analyzing
     expressions, like function calls).
 
-1. Map the violation struct to a rule code in `crates/ruff_linter/src/codes.rs` (e.g., `B011`).
+1. Register the violation struct in `crates/ruff_linter/src/codes.rs` (e.g., `B011`). If your lint
+    rule comes from an existing linter, you can map it to that linter and give it a code. Otherwise,
+    you can leave the linter and code blank, registering it only to a category. For example:
+
+    ```rust
+    // Rules with linter groups and codes
+    (Flake8Logging, "015") => rules::flake8_logging::rules::RootLoggerCall,
+
+    // Rules with only a category
+    () => rules::ruff::rules::PytestFixtureAutouse,
+    ```
 
 1. Add proper [testing](#rule-testing-fixtures-and-snapshots) for your rule.
 
@@ -244,11 +255,15 @@ Once you're satisfied with your code, add tests for your rule
 (see: [rule testing](#rule-testing-fixtures-and-snapshots)), and regenerate the documentation and
 associated assets (like our JSON Schema) with `cargo dev generate-all`.
 
-Finally, submit a pull request, and include the category, rule name, and rule code in the title, as
-in:
+Finally, submit a pull request, and include the category, rule name, and rule code (if applicable)
+in the title, as in:
 
 > \[`pycodestyle`\] Implement `redundant-backslash` (`E502`)
 
+or
+
+> \[`pedantic`\] Implement `pytest-fixture-autouse`
+
 #### Rule testing: fixtures and snapshots
 
 To test rules, Ruff uses the mdtest framework, initially developed for ty. Mdtests are written as

crates/ruff/src/commands/check.rs

@@ -258,7 +258,7 @@ mod test {
         }
 
         // Configure
-        let snapshot = format!("{}_{}", rule_code.noqa_code(), path);
+        let snapshot = format!("{}_{}", rule_code.name(), path);
         // invalid pyproject.toml is not active by default
         let settings = Settings {
             linter: LinterSettings::for_rules(vec![rule_code, Rule::InvalidPyprojectToml]),

crates/ruff/src/commands/format.rs

@@ -1105,7 +1105,7 @@ pub(super) fn warn_incompatible_formatter_settings(resolver: &Resolver) {
     if !incompatible_rules.is_empty() {
         let mut rule_names: Vec<_> = incompatible_rules
             .into_iter()
-            .map(|rule| format!("`{}`", rule.noqa_code()))
+            .map(|rule| format!("{:#}", rule.name_and_code()))
             .collect();
         rule_names.sort();
         if let [rule] = rule_names.as_slice() {

crates/ruff/src/commands/rule.rs

@@ -15,8 +15,8 @@ use crate::args::HelpFormat;
 #[derive(Serialize)]
 struct Explanation<'a> {
     name: &'a str,
-    code: String,
-    linter: &'a str,
+    code: Option<String>,
+    linter: Option<&'a str>,
     summary: &'a str,
     message_formats: &'a [&'a str],
     fix: String,
@@ -31,13 +31,16 @@ struct Explanation<'a> {
 
 impl<'a> Explanation<'a> {
     fn from_rule(rule: &'a Rule) -> Self {
-        let code = rule.noqa_code().to_string();
-        let (linter, _) = Linter::parse_code(&code).unwrap();
+        let code = rule.noqa_code().map(|code| code.to_string());
+        let linter = code
+            .as_deref()
+            .and_then(Linter::parse_code)
+            .map(|(linter, _)| linter.name());
         let fix = rule.fixable().to_string();
         Self {
             name: rule.name().as_str(),
             code,
-            linter: linter.name(),
+            linter,
             summary: rule.message_formats()[0],
             message_formats: rule.message_formats(),
             fix,
@@ -56,18 +59,22 @@ impl<'a> Explanation<'a> {
 
 fn format_rule_text(rule: Rule) -> String {
     let mut output = String::new();
-    let _ = write!(&mut output, "# {} ({})", rule.name(), rule.noqa_code());
+    let _ = write!(&mut output, "# {}", rule.name_and_code());
     output.push('\n');
     output.push('\n');
 
-    let (linter, _) = Linter::parse_code(&rule.noqa_code().to_string()).unwrap();
-    let _ = write!(
-        &mut output,
-        "Derived from the **{}** linter.",
-        linter.name()
-    );
-    output.push('\n');
-    output.push('\n');
+    if let Some(linter) = rule
+        .noqa_code()
+        .and_then(|code| Linter::parse_code(&code.to_string()).map(|(linter, _)| linter))
+    {
+        let _ = write!(
+            &mut output,
+            "Derived from the **{}** linter.",
+            linter.name()
+        );
+        output.push('\n');
+        output.push('\n');
+    }
 
     let fix_availability = rule.fixable();
     if matches!(

crates/ruff/src/diagnostics.rs

@@ -169,9 +169,9 @@ impl AddAssign for FixMap {
                 continue;
             }
             let fixed_in_file = self.0.entry(filename).or_default();
-            for (rule, name, count) in fixed.iter() {
+            for (id, code, count) in fixed.iter() {
                 if count > 0 {
-                    *fixed_in_file.entry(rule).or_default(name) += count;
+                    *fixed_in_file.entry(id).or_default(code) += count;
                 }
             }
         }

crates/ruff/src/printer.rs

@@ -52,7 +52,7 @@ impl ExpandedStatistics<'_> {
     }
 }
 
-/// Accumulator type for grouping diagnostics by code.
+/// Accumulator type for grouping diagnostics by name.
 /// Format: (`code`, `representative_diagnostic`, `total_count`, `fixable_count`)
 type DiagnosticGroup<'a> = (Option<&'a SecondaryCode>, &'a Diagnostic, usize, usize);
 
@@ -280,15 +280,15 @@ impl Printer {
         let statistics: Vec<ExpandedStatistics> = diagnostics
             .inner
             .iter()
-            .sorted_by_key(|diagnostic| diagnostic.secondary_code())
+            .sorted_by_key(|diagnostic| diagnostic.name())
             .fold(vec![], |mut acc: Vec<DiagnosticGroup>, diagnostic| {
                 let is_fixable = diagnostic
                     .fix()
                     .is_some_and(|fix| fix.applies(required_applicability));
                 let code = diagnostic.secondary_code();
 
-                if let Some((prev_code, _prev_message, count, fixable_count)) = acc.last_mut() {
-                    if *prev_code == code {
+                if let Some((_prev_code, prev_message, count, fixable_count)) = acc.last_mut() {
+                    if prev_message.name() == diagnostic.name() {
                         *count += 1;
                         if is_fixable {
                             *fixable_count += 1;
@@ -500,19 +500,18 @@ fn print_fix_summary(
             relativize_path(filename).bold(),
             ":".cyan()
         )?;
-        for (code, name, count) in table.iter().sorted_by_key(|(.., count)| Reverse(*count)) {
-            if is_human_readable_names_enabled(preview) && !prefer_rule_codes {
-                writeln!(
-                    writer,
-                    "    {count:>num_digits$} × {name} ({code})",
-                    name = name.to_string().red().bold(),
-                )?;
-            } else {
-                writeln!(
-                    writer,
-                    "    {count:>num_digits$} × {code} ({name})",
-                    code = code.to_string().red().bold(),
-                )?;
+        for (name, code, count) in table.iter().sorted_by_key(|(.., count)| Reverse(*count)) {
+            write!(writer, "    {count:>num_digits$} × ")?;
+            match code {
+                Some(code) if is_human_readable_names_enabled(preview) && !prefer_rule_codes => {
+                    writeln!(writer, "{name} ({code})", name = name.as_str().red().bold())?;
+                }
+                Some(code) => {
+                    writeln!(writer, "{code} ({name})", code = code.as_str().red().bold())?;
+                }
+                None => {
+                    writeln!(writer, "{name}", name = name.as_str().red().bold())?;
+                }
             }
         }
     }

crates/ruff/tests/cli/format.rs

@@ -1063,7 +1063,7 @@ if condition:
     	print('Should change quotes')
 
     ----- stderr -----
-    warning: The following rule may cause conflicts when used with the formatter: `COM812`. To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `lint.select` or `lint.extend-select` configuration, or adding it to the `lint.ignore` configuration.
+    warning: The following rule may cause conflicts when used with the formatter: `missing-trailing-comma` (`COM812`). To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `lint.select` or `lint.extend-select` configuration, or adding it to the `lint.ignore` configuration.
     "#);
     Ok(())
 }
@@ -1187,7 +1187,7 @@ def say_hy(name: str):
     1 file reformatted
 
     ----- stderr -----
-    warning: The following rule may cause conflicts when used with the formatter: `COM812`. To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `lint.select` or `lint.extend-select` configuration, or adding it to the `lint.ignore` configuration.
+    warning: The following rule may cause conflicts when used with the formatter: `missing-trailing-comma` (`COM812`). To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `lint.select` or `lint.extend-select` configuration, or adding it to the `lint.ignore` configuration.
     warning: The `format.indent-style="tab"` option is incompatible with `W191`, which lints against all uses of tabs. We recommend disabling these rules when using the formatter, which enforces a consistent indentation style. Alternatively, set the `format.indent-style` option to `"space"`.
     warning: The `lint.flake8-implicit-str-concat.allow-multiline = false` option is incompatible with the formatter unless `ISC001` is enabled. We recommend enabling `ISC001` or setting `allow-multiline=true`.
     warning: The `format.indent-style="tab"` option is incompatible with `D206`, with requires space-based indentation. We recommend disabling these rules when using the formatter, which enforces a consistent indentation style. Alternatively, set the `format.indent-style` option to `"space"`.
@@ -1245,7 +1245,7 @@ def say_hy(name: str):
     	print(f"Hy {name}")
 
     ----- stderr -----
-    warning: The following rule may cause conflicts when used with the formatter: `COM812`. To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `lint.select` or `lint.extend-select` configuration, or adding it to the `lint.ignore` configuration.
+    warning: The following rule may cause conflicts when used with the formatter: `missing-trailing-comma` (`COM812`). To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `lint.select` or `lint.extend-select` configuration, or adding it to the `lint.ignore` configuration.
     warning: The `format.indent-style="tab"` option is incompatible with `W191`, which lints against all uses of tabs. We recommend disabling these rules when using the formatter, which enforces a consistent indentation style. Alternatively, set the `format.indent-style` option to `"space"`.
     warning: The `format.indent-style="tab"` option is incompatible with `D206`, with requires space-based indentation. We recommend disabling these rules when using the formatter, which enforces a consistent indentation style. Alternatively, set the `format.indent-style` option to `"space"`.
     warning: The `flake8-quotes.inline-quotes="single"` option is incompatible with the formatter's `format.quote-style="double"`. We recommend disabling `Q000` and `Q003` when using the formatter, which enforces a consistent quote style. Alternatively, set both options to either `"single"` or `"double"`.
@@ -1378,7 +1378,7 @@ def say_hy(name: str):
     ----- stderr -----
     warning: `incorrect-blank-line-before-class` (D203) and `no-blank-line-before-class` (D211) are incompatible. Ignoring `incorrect-blank-line-before-class`.
     warning: `multi-line-summary-first-line` (D212) and `multi-line-summary-second-line` (D213) are incompatible. Ignoring `multi-line-summary-second-line`.
-    warning: The following rule may cause conflicts when used with the formatter: `COM812`. To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `lint.select` or `lint.extend-select` configuration, or adding it to the `lint.ignore` configuration.
+    warning: The following rule may cause conflicts when used with the formatter: `missing-trailing-comma` (`COM812`). To avoid unexpected behavior, we recommend disabling this rule, either by removing it from the `lint.select` or `lint.extend-select` configuration, or adding it to the `lint.ignore` configuration.
     ");
     Ok(())
 }

crates/ruff_dev/src/generate_default_rules.rs

@@ -35,7 +35,7 @@ pub(crate) fn generate() -> String {
         output.push_str("        select = [\n");
         for (_, rules) in &linters {
             for rule in rules {
-                let _ = writeln!(output, "            \"{}\",", rule.noqa_code());
+                let _ = writeln!(output, "            \"{}\",", rule.noqa_code().unwrap());
             }
         }
         output.push_str("        ]\n");
@@ -56,7 +56,7 @@ pub(crate) fn generate() -> String {
 
         for rule in rules {
             let name = rule.name();
-            let code = rule.noqa_code();
+            let code = rule.noqa_code().unwrap();
             let _ = writeln!(output, "- [`{name}`](rules/{name}.md) (`{code}`)");
         }
         output.push('\n');

crates/ruff_dev/src/generate_docs.rs

@@ -30,7 +30,7 @@ pub(crate) fn main(args: &Args) -> Result<()> {
         if let Some(explanation) = rule.explanation() {
             let mut output = String::new();
 
-            let _ = writeln!(&mut output, "# {} ({})", rule.name(), rule.noqa_code());
+            let _ = writeln!(&mut output, "# {}", rule.name_and_code());
 
             let status_text = match rule.status() {
                 RuleStatus::Stable { since } => {
@@ -55,26 +55,36 @@ pub(crate) fn main(args: &Args) -> Result<()> {
                 }
             };
 
+            let issue_search = format!(
+                "(%27{encoded_name}%27{code})",
+                encoded_name =
+                    url::form_urlencoded::byte_serialize(rule.name().as_str().as_bytes())
+                        .collect::<String>(),
+                code = rule
+                    .noqa_code()
+                    .map(|code| format!("%20OR%20{code}"))
+                    .unwrap_or_default(),
+            );
+
             let _ = writeln!(
                 &mut output,
                 r#"<small>
 {status_text} ·
-<a href="https://github.com/astral-sh/ruff/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20(%27{encoded_name}%27%20OR%20{rule_code})" target="_blank">Related issues</a> ·
+<a href="https://github.com/astral-sh/ruff/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20{issue_search}" target="_blank">Related issues</a> ·
 <a href="https://github.com/astral-sh/ruff/blob/main/{file}#L{line}" target="_blank">View source</a>
 </small>
 
 "#,
-                encoded_name =
-                    url::form_urlencoded::byte_serialize(rule.name().as_str().as_bytes())
-                        .collect::<String>(),
-                rule_code = rule.noqa_code(),
                 file =
                     url::form_urlencoded::byte_serialize(rule.file().replace('\\', "/").as_bytes())
                         .collect::<String>(),
                 line = rule.line(),
             );
-            let (linter, _) = Linter::parse_code(&rule.noqa_code().to_string()).unwrap();
-            if linter.url().is_some() {
+            if let Some(linter) = rule
+                .noqa_code()
+                .and_then(|code| Linter::parse_code(&code.to_string()).map(|(linter, _)| linter))
+                .filter(|linter| linter.url().is_some())
+            {
                 let common_prefix: String = match linter.common_prefix() {
                     "" => linter
                         .upstream_categories()
@@ -134,11 +144,7 @@ pub(crate) fn main(args: &Args) -> Result<()> {
                 output.push('\n');
             }
 
-            process_documentation(
-                explanation.trim(),
-                &mut output,
-                &rule.noqa_code().to_string(),
-            );
+            process_documentation(explanation.trim(), &mut output, rule.name().as_str());
 
             let filename = PathBuf::from(ROOT_DIR)
                 .join("docs")