Add ruff rule --all subcommand (with JSON output support)

crates/ruff_cli/src/args.rs

@@ -35,11 +35,15 @@ pub struct Args {
 pub enum Command {
     /// Run Ruff on the given files or directories (default).
     Check(CheckArgs),
-    /// Explain a rule.
+    /// Explain a rule (or all rules).
     #[clap(alias = "--explain")]
     Rule {
         #[arg(value_parser=Rule::from_code)]
-        rule: Rule,
+        rule: Option<Rule>,
+
+        /// Explain all rules
+        #[arg(long, conflicts_with = "rule")]
+        all: bool,
 
         /// Output format
         #[arg(long, value_enum, default_value = "text")]

crates/ruff_cli/src/commands/rule.rs

@@ -1,7 +1,9 @@
 use std::io::{self, BufWriter, Write};
 
 use anyhow::Result;
-use serde::Serialize;
+use serde::ser::SerializeSeq;
+use serde::{Serialize, Serializer};
+use strum::IntoEnumIterator;
 
 use ruff::registry::{Linter, Rule, RuleNamespace};
 use ruff_diagnostics::AutofixKind;
@@ -88,3 +90,25 @@ pub(crate) fn rule(rule: Rule, format: HelpFormat) -> Result<()> {
     };
     Ok(())
 }
+
+/// Explain all rules to the user.
+pub(crate) fn rules(format: HelpFormat) -> Result<()> {
+    let mut stdout = BufWriter::new(io::stdout().lock());
+    match format {
+        HelpFormat::Text => {
+            for rule in Rule::iter() {
+                writeln!(stdout, "{}", format_rule_text(rule))?;
+                writeln!(stdout)?;
+            }
+        }
+        HelpFormat::Json => {
+            let mut serializer = serde_json::Serializer::pretty(stdout);
+            let mut seq = serializer.serialize_seq(None)?;
+            for rule in Rule::iter() {
+                seq.serialize_element(&rule_to_explanation(&rule))?;
+            }
+            seq.end()?;
+        }
+    }
+    Ok(())
+}

crates/ruff_cli/src/lib.rs

@@ -113,7 +113,18 @@ quoting the executed command, along with the relevant file contents and `pyproje
     set_up_logging(&log_level)?;
 
     match command {
-        Command::Rule { rule, format } => commands::rule::rule(rule, format)?,
+        Command::Rule { rule, all, format } => {
+            if all {
+                commands::rule::rules(format)?
+            } else {
+                match rule {
+                    Some(rule) => commands::rule::rule(rule, format)?,
+                    None => {
+                        return Err(anyhow::anyhow!("No rule or --all specified"));
+                    }
+                }
+            }
+        }
         Command::Config { option } => return Ok(commands::config::config(option.as_deref())),
         Command::Linter { format } => commands::linter::linter(format)?,
         Command::Clean => commands::clean::clean(log_level)?,

docs/configuration.md

@@ -164,6 +164,7 @@ Usage: ruff [OPTIONS] <COMMAND>
 Commands:
   check   Run Ruff on the given files or directories (default)
   rule    Explain a rule
+  rules   Explain all rules known to Ruff
   config  List or describe the available configuration options
   linter  List all supported upstream linters
   clean   Clear any caches in the current directory and any subdirectories