Create per-rule pages and link from README (#2644)

.gitignore

@@ -1,7 +1,8 @@
 # Local cache
 .ruff_cache
 crates/ruff/resources/test/cpython
-docs/
+docs/*
+!docs/rules
 mkdocs.yml
 .overrides
 

README.md

@@ -957,7 +957,7 @@ For more, see [flake8-bugbear](https://pypi.org/project/flake8-bugbear/) on PyPI
 | B014 | duplicate-handler-exception | Exception handler with duplicate exception: `{name}` | 🛠 |
 | B015 | useless-comparison | Pointless comparison. This comparison does nothing but waste CPU instructions. Either prepend `assert` or remove it. |  |
 | B016 | cannot-raise-literal | Cannot raise a literal. Did you intend to return it or raise an Exception? |  |
-| B017 | no-assert-raises-exception | `assertRaises(Exception)` should be considered evil |  |
+| [B017](https://github.com/charliermarsh/ruff/blob/main/docs/rules/assert-raises-exception.md) | [assert-raises-exception](https://github.com/charliermarsh/ruff/blob/main/docs/rules/assert-raises-exception.md) | `assertRaises(Exception)` should be considered evil |  |
 | B018 | useless-expression | Found useless expression. Either assign it to a variable or remove it. |  |
 | B019 | cached-instance-method | Use of `functools.lru_cache` or `functools.cache` on methods can lead to memory leaks |  |
 | B020 | loop-variable-overrides-iterator | Loop control variable `{name}` overrides iterable it iterates |  |

crates/ruff/src/checkers/ast.rs

@@ -1563,7 +1563,7 @@ where
                 }
             }
             StmtKind::With { items, body, .. } => {
-                if self.settings.rules.enabled(&Rule::NoAssertRaisesException) {
+                if self.settings.rules.enabled(&Rule::AssertRaisesException) {
                     flake8_bugbear::rules::assert_raises_exception(self, stmt, items);
                 }
                 if self

crates/ruff/src/registry.rs

@@ -146,7 +146,7 @@ ruff_macros::define_rule_mapping!(
     B014 => rules::flake8_bugbear::rules::DuplicateHandlerException,
     B015 => rules::flake8_bugbear::rules::UselessComparison,
     B016 => rules::flake8_bugbear::rules::CannotRaiseLiteral,
-    B017 => rules::flake8_bugbear::rules::NoAssertRaisesException,
+    B017 => rules::flake8_bugbear::rules::AssertRaisesException,
     B018 => rules::flake8_bugbear::rules::UselessExpression,
     B019 => rules::flake8_bugbear::rules::CachedInstanceMethod,
     B020 => rules::flake8_bugbear::rules::LoopVariableOverridesIterator,

crates/ruff/src/rules/flake8_bugbear/mod.rs

@@ -29,7 +29,7 @@ mod tests {
     #[test_case(Rule::DuplicateHandlerException, Path::new("B014.py"); "B014")]
     #[test_case(Rule::UselessComparison, Path::new("B015.py"); "B015")]
     #[test_case(Rule::CannotRaiseLiteral, Path::new("B016.py"); "B016")]
-    #[test_case(Rule::NoAssertRaisesException, Path::new("B017.py"); "B017")]
+    #[test_case(Rule::AssertRaisesException, Path::new("B017.py"); "B017")]
     #[test_case(Rule::UselessExpression, Path::new("B018.py"); "B018")]
     #[test_case(Rule::CachedInstanceMethod, Path::new("B019.py"); "B019")]
     #[test_case(Rule::LoopVariableOverridesIterator, Path::new("B020.py"); "B020")]

crates/ruff/src/rules/flake8_bugbear/rules/assert_raises_exception.rs

@@ -10,15 +10,25 @@ define_violation!(
     /// ### What it does
     /// Checks for `self.assertRaises(Exception)`.
     ///
-    /// ## Why is this bad?
+    /// ### Why is this bad?
     /// `assertRaises(Exception)` can lead to your test passing even if the
     /// code being tested is never executed due to a typo.
     ///
     /// Either assert for a more specific exception (builtin or custom), use
     /// `assertRaisesRegex` or the context manager form of `assertRaises`.
-    pub struct NoAssertRaisesException;
+    ///
+    /// ### Example
+    /// ```python
+    /// self.assertRaises(Exception, foo)
+    /// ```
+    ///
+    /// Use instead:
+    /// ```python
+    /// self.assertRaises(SomeSpecificException, foo)
+    /// ```
+    pub struct AssertRaisesException;
 );
-impl Violation for NoAssertRaisesException {
+impl Violation for AssertRaisesException {
     #[derive_message_formats]
     fn message(&self) -> String {
         format!("`assertRaises(Exception)` should be considered evil")
@@ -51,7 +61,7 @@ pub fn assert_raises_exception(checker: &mut Checker, stmt: &Stmt, items: &[With
     }
 
     checker.diagnostics.push(Diagnostic::new(
-        NoAssertRaisesException,
+        AssertRaisesException,
         Range::from_located(stmt),
     ));
 }

crates/ruff/src/rules/flake8_bugbear/rules/mod.rs

@@ -3,7 +3,7 @@ pub use abstract_base_class::{
     EmptyMethodWithoutAbstractDecorator,
 };
 pub use assert_false::{assert_false, DoNotAssertFalse};
-pub use assert_raises_exception::{assert_raises_exception, NoAssertRaisesException};
+pub use assert_raises_exception::{assert_raises_exception, AssertRaisesException};
 pub use assignment_to_os_environ::{assignment_to_os_environ, AssignmentToOsEnviron};
 pub use cached_instance_method::{cached_instance_method, CachedInstanceMethod};
 pub use cannot_raise_literal::{cannot_raise_literal, CannotRaiseLiteral};

crates/ruff/src/rules/flake8_bugbear/snapshots/ruff__rules__flake8_bugbear__tests__B017_B017.py.snap

@@ -1,9 +1,9 @@
 ---
-source: src/rules/flake8_bugbear/mod.rs
+source: crates/ruff/src/rules/flake8_bugbear/mod.rs
 expression: diagnostics
 ---
 - kind:
-    NoAssertRaisesException: ~
+    AssertRaisesException: ~
   location:
     row: 22
     column: 8

crates/ruff_cli/src/commands.rs

@@ -278,25 +278,31 @@ pub fn rule(rule: &Rule, format: HelpFormat) -> Result<()> {
     let mut stdout = BufWriter::new(io::stdout().lock());
     match format {
         HelpFormat::Text => {
-            writeln!(stdout, "{}\n", rule.as_ref())?;
-            writeln!(stdout, "Code: {} ({})\n", rule.code(), linter.name())?;
-
+            writeln!(
+                stdout,
+                "[{}] {} ({})",
+                linter.name(),
+                rule.as_ref(),
+                rule.code(),
+            )?;
+            writeln!(stdout)?;
             if let Some(explanation) = rule.explanation() {
-                writeln!(stdout, "{}\n", explanation)?;
+                writeln!(stdout, "{}", explanation.trim())?;
             } else {
-                writeln!(stdout, "Message formats:\n")?;
+                writeln!(stdout, "Message formats:")?;
                 for format in rule.message_formats() {
                     writeln!(stdout, "* {format}")?;
                 }
             }
 
             if let Some(autofix) = rule.autofixable() {
+                writeln!(stdout)?;
                 writeln!(
                     stdout,
                     "{}",
                     match autofix.available {
-                        AutofixAvailability::Sometimes => "Autofix is sometimes available.\n",
-                        AutofixAvailability::Always => "Autofix is always available.\n",
+                        AutofixAvailability::Sometimes => "Autofix is sometimes available.",
+                        AutofixAvailability::Always => "Autofix is always available.",
                     }
                 )?;
             }

crates/ruff_dev/src/generate_all.rs

@@ -2,7 +2,9 @@
 
 use anyhow::Result;
 
-use crate::{generate_cli_help, generate_json_schema, generate_options, generate_rules_table};
+use crate::{
+    generate_cli_help, generate_docs, generate_json_schema, generate_options, generate_rules_table,
+};
 
 #[derive(clap::Args)]
 pub struct Args {
@@ -12,6 +14,9 @@ pub struct Args {
 }
 
 pub fn main(args: &Args) -> Result<()> {
+    generate_docs::main(&generate_docs::Args {
+        dry_run: args.dry_run,
+    })?;
     generate_json_schema::main(&generate_json_schema::Args {
         dry_run: args.dry_run,
     })?;

crates/ruff_dev/src/generate_docs.rs

@@ -1 +1,32 @@
+//! Generate Markdown documentation for applicable rules.
+#![allow(clippy::print_stdout, clippy::print_stderr)]
 
+use std::fs;
+
+use anyhow::Result;
+use strum::IntoEnumIterator;
+
+use ruff::registry::Rule;
+
+#[derive(clap::Args)]
+pub struct Args {
+    /// Write the generated docs to stdout (rather than to the filesystem).
+    #[arg(long)]
+    pub(crate) dry_run: bool,
+}
+
+pub fn main(args: &Args) -> Result<()> {
+    for rule in Rule::iter() {
+        if let Some(explanation) = rule.explanation() {
+            let explanation = format!("# {} ({})\n\n{}", rule.as_ref(), rule.code(), explanation);
+
+            if args.dry_run {
+                println!("{}", explanation);
+            } else {
+                fs::create_dir_all("docs/rules")?;
+                fs::write(format!("docs/rules/{}.md", rule.as_ref()), explanation)?;
+            }
+        }
+    }
+    Ok(())
+}

crates/ruff_dev/src/generate_rules_table.rs

@@ -14,6 +14,8 @@ const TABLE_END_PRAGMA: &str = "<!-- End auto-generated sections. -->";
 const TOC_BEGIN_PRAGMA: &str = "<!-- Begin auto-generated table of contents. -->";
 const TOC_END_PRAGMA: &str = "<!-- End auto-generated table of contents. -->";
 
+const URL_PREFIX: &str = "https://github.com/charliermarsh/ruff/blob/main/docs/rules";
+
 #[derive(clap::Args)]
 pub struct Args {
     /// Write the generated table to stdout (rather than to `README.md`).
@@ -32,13 +34,27 @@ fn generate_table(table_out: &mut String, rules: impl IntoIterator<Item = Rule>)
             Some(_) => "🛠",
         };
 
-        table_out.push_str(&format!(
-            "| {} | {} | {} | {} |",
-            rule.code(),
-            rule.as_ref(),
-            rule.message_formats()[0].replace('|', r"\|"),
-            fix_token
-        ));
+        if rule.explanation().is_some() {
+            table_out.push_str(&format!(
+                "| [{}]({}/{}.md) | [{}]({}/{}.md) | {} | {} |",
+                rule.code(),
+                URL_PREFIX,
+                rule.as_ref(),
+                rule.as_ref(),
+                URL_PREFIX,
+                rule.as_ref(),
+                rule.message_formats()[0].replace('|', r"\|"),
+                fix_token
+            ));
+        } else {
+            table_out.push_str(&format!(
+                "| {} | {} | {} | {} |",
+                rule.code(),
+                rule.as_ref(),
+                rule.message_formats()[0].replace('|', r"\|"),
+                fix_token
+            ));
+        }
         table_out.push('\n');
     }
     table_out.push('\n');

crates/ruff_dev/src/main.rs

@@ -39,6 +39,8 @@ enum Command {
     GenerateOptions(generate_options::Args),
     /// Generate CLI help.
     GenerateCliHelp(generate_cli_help::Args),
+    /// Generate Markdown docs.
+    GenerateDocs(generate_docs::Args),
     /// Print the AST for a given Python file.
     PrintAST(print_ast::Args),
     /// Print the LibCST CST for a given Python file.
@@ -57,6 +59,7 @@ fn main() -> Result<()> {
         Command::GenerateRulesTable(args) => generate_rules_table::main(args)?,
         Command::GenerateOptions(args) => generate_options::main(args)?,
         Command::GenerateCliHelp(args) => generate_cli_help::main(args)?,
+        Command::GenerateDocs(args) => generate_docs::main(args)?,
         Command::PrintAST(args) => print_ast::main(args)?,
         Command::PrintCST(args) => print_cst::main(args)?,
         Command::PrintTokens(args) => print_tokens::main(args)?,

crates/ruff_macros/src/define_violation.rs

@@ -37,7 +37,8 @@ impl Parse for LintMeta {
                 let value = lit.value();
                 let line = value.strip_prefix(' ').unwrap_or(&value);
                 if line.starts_with("```") {
-                    explanation += "```\n";
+                    explanation += line;
+                    explanation.push('\n');
                     in_code = !in_code;
                 } else if !(in_code && line.starts_with("# ")) {
                     explanation += line;
@@ -61,15 +62,21 @@ impl Parse for LintMeta {
 
 pub fn define_violation(input: &TokenStream, meta: LintMeta) -> TokenStream {
     let LintMeta { explanation, name } = meta;
-    let output = quote! {
-        #[derive(Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
-        #input
+    if explanation.is_empty() {
+        quote! {
+            #[derive(Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+            #input
+        }
+    } else {
+        quote! {
+            #[derive(Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+            #input
 
-        impl #name {
-            pub fn explanation() -> Option<&'static str> {
-                Some(#explanation)
+            impl #name {
+                pub fn explanation() -> Option<&'static str> {
+                    Some(#explanation)
+                }
             }
         }
-    };
-    output
+    }
 }

docs/rules/assert-raises-exception.md

@@ -0,0 +1,21 @@
+# assert-raises-exception (B017)
+
+### What it does
+Checks for the use of `assertRaises(Exception)`.
+
+### Why is this bad?
+`assertRaises(Exception)` can lead to your test passing even if the
+code being tested is never executed (e.g., due to a typo).
+
+Assert for a more specific exception (builtin or custom), use
+`assertRaisesRegex` or the context manager form of `assertRaises`.
+
+### Example
+```python
+self.assertRaises(Exception, foo)
+```
+
+Use instead:
+```python
+self.assertRaises(SomeSpecificException, foo)
+```

scripts/add_rule.py

@@ -21,10 +21,15 @@ def snake_case(name: str) -> str:
     ).lstrip("_")
 
 
-def main(*, name: str, code: str, linter: str) -> None:  # noqa: PLR0915
+def main(*, name: str, code: str, linter: str) -> None:
     """Generate boilerplate for a new rule."""
     # Create a test fixture.
-    with (ROOT_DIR / "crates/ruff/resources/test/fixtures" / dir_name(linter) / f"{code}.py").open(
+    with (
+        ROOT_DIR
+        / "crates/ruff/resources/test/fixtures"
+        / dir_name(linter)
+        / f"{code}.py"
+    ).open(
         "a",
     ):
         pass

scripts/generate_mkdocs.py

@@ -36,6 +36,12 @@ def main() -> None:
         raise ValueError(msg)
     content = content.replace(DOCUMENTATION_LINK, "")
 
+    # Replace all GitHub links with relative links.
+    content = content.replace(
+        "https://github.com/charliermarsh/ruff/blob/main/docs/rules/",
+        "rules/",
+    )
+
     Path("docs").mkdir(parents=True, exist_ok=True)
 
     # Split the README.md into sections.
@@ -71,8 +77,13 @@ def main() -> None:
     ]
     config["extra"] = {"analytics": {"provider": "fathom"}}
 
-    Path(".overrides/partials/integrations/analytics").mkdir(parents=True, exist_ok=True)
-    with Path(".overrides/partials/integrations/analytics/fathom.html").open("w+") as fp:
+    Path(".overrides/partials/integrations/analytics").mkdir(
+        parents=True,
+        exist_ok=True,
+    )
+    with Path(".overrides/partials/integrations/analytics/fathom.html").open(
+        "w+",
+    ) as fp:
         fp.write(FATHOM_SCRIPT)
 
     with Path("mkdocs.yml").open("w+") as fp: