Make preview part of the selector API

crates/flake8_to_ruff/src/plugin.rs

@@ -4,6 +4,7 @@ use std::str::FromStr;
 
 use anyhow::anyhow;
 use ruff::registry::Linter;
+use ruff::settings::types::PreviewMode;
 use ruff::RuleSelector;
 
 #[derive(Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
@@ -331,7 +332,7 @@ pub(crate) fn infer_plugins_from_codes(selectors: &HashSet<RuleSelector>) -> Vec
     .filter(|plugin| {
         for selector in selectors {
             if selector
-                .into_iter()
+                .rules(PreviewMode::Disabled)
                 .any(|rule| Linter::from(plugin).rules().any(|r| r == rule))
             {
                 return true;

crates/ruff/src/codes.rs

@@ -51,8 +51,8 @@ impl PartialEq<&str> for NoqaCode {
 pub enum RuleGroup {
     /// The rule has not been assigned to any specific group.
     Unspecified,
-    /// The rule is still under development, and must be enabled explicitly.
-    Nursery,
+    /// The rule is unstable, and must be enabled explicitly or by enabling preview.
+    Preview,
 }
 
 #[ruff_macros::map_codes]
@@ -64,39 +64,39 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
     Some(match (linter, code) {
         // pycodestyle errors
         (Pycodestyle, "E101") => (RuleGroup::Unspecified, rules::pycodestyle::rules::MixedSpacesAndTabs),
-        (Pycodestyle, "E111") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::IndentationWithInvalidMultiple),
-        (Pycodestyle, "E112") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::NoIndentedBlock),
-        (Pycodestyle, "E113") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::UnexpectedIndentation),
-        (Pycodestyle, "E114") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::IndentationWithInvalidMultipleComment),
-        (Pycodestyle, "E115") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::NoIndentedBlockComment),
-        (Pycodestyle, "E116") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::UnexpectedIndentationComment),
-        (Pycodestyle, "E117") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::OverIndented),
-        (Pycodestyle, "E201") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::WhitespaceAfterOpenBracket),
-        (Pycodestyle, "E202") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::WhitespaceBeforeCloseBracket),
-        (Pycodestyle, "E203") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::WhitespaceBeforePunctuation),
-        (Pycodestyle, "E211") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::WhitespaceBeforeParameters),
-        (Pycodestyle, "E221") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MultipleSpacesBeforeOperator),
-        (Pycodestyle, "E222") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MultipleSpacesAfterOperator),
-        (Pycodestyle, "E223") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::TabBeforeOperator),
-        (Pycodestyle, "E224") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::TabAfterOperator),
-        (Pycodestyle, "E225") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundOperator),
-        (Pycodestyle, "E226") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundArithmeticOperator),
-        (Pycodestyle, "E227") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundBitwiseOrShiftOperator),
-        (Pycodestyle, "E228") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundModuloOperator),
-        (Pycodestyle, "E231") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MissingWhitespace),
-        (Pycodestyle, "E241") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MultipleSpacesAfterComma),
-        (Pycodestyle, "E242") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::TabAfterComma),
-        (Pycodestyle, "E251") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::UnexpectedSpacesAroundKeywordParameterEquals),
-        (Pycodestyle, "E252") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundParameterEquals),
-        (Pycodestyle, "E261") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::TooFewSpacesBeforeInlineComment),
-        (Pycodestyle, "E262") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::NoSpaceAfterInlineComment),
-        (Pycodestyle, "E265") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::NoSpaceAfterBlockComment),
-        (Pycodestyle, "E266") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MultipleLeadingHashesForBlockComment),
-        (Pycodestyle, "E271") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MultipleSpacesAfterKeyword),
-        (Pycodestyle, "E272") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MultipleSpacesBeforeKeyword),
-        (Pycodestyle, "E273") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::TabAfterKeyword),
-        (Pycodestyle, "E274") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::TabBeforeKeyword),
-        (Pycodestyle, "E275") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAfterKeyword),
+        (Pycodestyle, "E111") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::IndentationWithInvalidMultiple),
+        (Pycodestyle, "E112") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::NoIndentedBlock),
+        (Pycodestyle, "E113") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::UnexpectedIndentation),
+        (Pycodestyle, "E114") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::IndentationWithInvalidMultipleComment),
+        (Pycodestyle, "E115") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::NoIndentedBlockComment),
+        (Pycodestyle, "E116") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::UnexpectedIndentationComment),
+        (Pycodestyle, "E117") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::OverIndented),
+        (Pycodestyle, "E201") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::WhitespaceAfterOpenBracket),
+        (Pycodestyle, "E202") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::WhitespaceBeforeCloseBracket),
+        (Pycodestyle, "E203") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::WhitespaceBeforePunctuation),
+        (Pycodestyle, "E211") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::WhitespaceBeforeParameters),
+        (Pycodestyle, "E221") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MultipleSpacesBeforeOperator),
+        (Pycodestyle, "E222") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MultipleSpacesAfterOperator),
+        (Pycodestyle, "E223") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::TabBeforeOperator),
+        (Pycodestyle, "E224") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::TabAfterOperator),
+        (Pycodestyle, "E225") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundOperator),
+        (Pycodestyle, "E226") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundArithmeticOperator),
+        (Pycodestyle, "E227") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundBitwiseOrShiftOperator),
+        (Pycodestyle, "E228") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundModuloOperator),
+        (Pycodestyle, "E231") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MissingWhitespace),
+        (Pycodestyle, "E241") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MultipleSpacesAfterComma),
+        (Pycodestyle, "E242") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::TabAfterComma),
+        (Pycodestyle, "E251") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::UnexpectedSpacesAroundKeywordParameterEquals),
+        (Pycodestyle, "E252") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAroundParameterEquals),
+        (Pycodestyle, "E261") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::TooFewSpacesBeforeInlineComment),
+        (Pycodestyle, "E262") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::NoSpaceAfterInlineComment),
+        (Pycodestyle, "E265") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::NoSpaceAfterBlockComment),
+        (Pycodestyle, "E266") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MultipleLeadingHashesForBlockComment),
+        (Pycodestyle, "E271") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MultipleSpacesAfterKeyword),
+        (Pycodestyle, "E272") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MultipleSpacesBeforeKeyword),
+        (Pycodestyle, "E273") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::TabAfterKeyword),
+        (Pycodestyle, "E274") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::TabBeforeKeyword),
+        (Pycodestyle, "E275") => (RuleGroup::Preview, rules::pycodestyle::rules::logical_lines::MissingWhitespaceAfterKeyword),
         (Pycodestyle, "E401") => (RuleGroup::Unspecified, rules::pycodestyle::rules::MultipleImportsOnOneLine),
         (Pycodestyle, "E402") => (RuleGroup::Unspecified, rules::pycodestyle::rules::ModuleImportNotAtTopOfFile),
         (Pycodestyle, "E501") => (RuleGroup::Unspecified, rules::pycodestyle::rules::LineTooLong),
@@ -176,7 +176,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pylint, "C0205") => (RuleGroup::Unspecified, rules::pylint::rules::SingleStringSlots),
         (Pylint, "C0208") => (RuleGroup::Unspecified, rules::pylint::rules::IterationOverSet),
         (Pylint, "C0414") => (RuleGroup::Unspecified, rules::pylint::rules::UselessImportAlias),
-        (Pylint, "C1901") => (RuleGroup::Nursery, rules::pylint::rules::CompareToEmptyString),
+        (Pylint, "C1901") => (RuleGroup::Preview, rules::pylint::rules::CompareToEmptyString),
         (Pylint, "C3002") => (RuleGroup::Unspecified, rules::pylint::rules::UnnecessaryDirectLambdaCall),
         (Pylint, "E0100") => (RuleGroup::Unspecified, rules::pylint::rules::YieldInInit),
         (Pylint, "E0101") => (RuleGroup::Unspecified, rules::pylint::rules::ReturnInInit),
@@ -216,7 +216,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pylint, "R1722") => (RuleGroup::Unspecified, rules::pylint::rules::SysExitAlias),
         (Pylint, "R2004") => (RuleGroup::Unspecified, rules::pylint::rules::MagicValueComparison),
         (Pylint, "R5501") => (RuleGroup::Unspecified, rules::pylint::rules::CollapsibleElseIf),
-        (Pylint, "R6301") => (RuleGroup::Nursery, rules::pylint::rules::NoSelfUse),
+        (Pylint, "R6301") => (RuleGroup::Preview, rules::pylint::rules::NoSelfUse),
         (Pylint, "W0120") => (RuleGroup::Unspecified, rules::pylint::rules::UselessElseOnLoop),
         (Pylint, "W0127") => (RuleGroup::Unspecified, rules::pylint::rules::SelfAssigningVariable),
         (Pylint, "W0129") => (RuleGroup::Unspecified, rules::pylint::rules::AssertOnStringLiteral),
@@ -228,9 +228,9 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Pylint, "W1508") => (RuleGroup::Unspecified, rules::pylint::rules::InvalidEnvvarDefault),
         (Pylint, "W1509") => (RuleGroup::Unspecified, rules::pylint::rules::SubprocessPopenPreexecFn),
         (Pylint, "W1510") => (RuleGroup::Unspecified, rules::pylint::rules::SubprocessRunWithoutCheck),
-        (Pylint, "W1641") => (RuleGroup::Nursery, rules::pylint::rules::EqWithoutHash),
+        (Pylint, "W1641") => (RuleGroup::Preview, rules::pylint::rules::EqWithoutHash),
         (Pylint, "W2901") => (RuleGroup::Unspecified, rules::pylint::rules::RedefinedLoopName),
-        (Pylint, "W3201") => (RuleGroup::Nursery, rules::pylint::rules::BadDunderMethodName),
+        (Pylint, "W3201") => (RuleGroup::Preview, rules::pylint::rules::BadDunderMethodName),
         (Pylint, "W3301") => (RuleGroup::Unspecified, rules::pylint::rules::NestedMinMax),
 
         // flake8-async
@@ -403,7 +403,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Flake8Simplify, "910") => (RuleGroup::Unspecified, rules::flake8_simplify::rules::DictGetWithNoneDefault),
 
         // flake8-copyright
-        (Flake8Copyright, "001") => (RuleGroup::Nursery, rules::flake8_copyright::rules::MissingCopyrightNotice),
+        (Flake8Copyright, "001") => (RuleGroup::Preview, rules::flake8_copyright::rules::MissingCopyrightNotice),
 
         // pyupgrade
         (Pyupgrade, "001") => (RuleGroup::Unspecified, rules::pyupgrade::rules::UselessMetaclassType),
@@ -815,10 +815,10 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Ruff, "012") => (RuleGroup::Unspecified, rules::ruff::rules::MutableClassDefault),
         (Ruff, "013") => (RuleGroup::Unspecified, rules::ruff::rules::ImplicitOptional),
         #[cfg(feature = "unreachable-code")] // When removing this feature gate, also update rules_selector.rs
-        (Ruff, "014") => (RuleGroup::Nursery, rules::ruff::rules::UnreachableCode),
+        (Ruff, "014") => (RuleGroup::Preview, rules::ruff::rules::UnreachableCode),
         (Ruff, "015") => (RuleGroup::Unspecified, rules::ruff::rules::UnnecessaryIterableAllocationForFirstElement),
         (Ruff, "016") => (RuleGroup::Unspecified, rules::ruff::rules::InvalidIndexType),
-        (Ruff, "017") => (RuleGroup::Nursery, rules::ruff::rules::QuadraticListSummation),
+        (Ruff, "017") => (RuleGroup::Preview, rules::ruff::rules::QuadraticListSummation),
         (Ruff, "100") => (RuleGroup::Unspecified, rules::ruff::rules::UnusedNOQA),
         (Ruff, "200") => (RuleGroup::Unspecified, rules::ruff::rules::InvalidPyprojectToml),
 
@@ -866,9 +866,9 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Flake8Slots, "002") => (RuleGroup::Unspecified, rules::flake8_slots::rules::NoSlotsInNamedtupleSubclass),
 
         // refurb
-        (Refurb, "113") => (RuleGroup::Nursery, rules::refurb::rules::RepeatedAppend),
-        (Refurb, "131") => (RuleGroup::Nursery, rules::refurb::rules::DeleteFullSlice),
-        (Refurb, "132") => (RuleGroup::Nursery, rules::refurb::rules::CheckAndRemoveFromSet),
+        (Refurb, "113") => (RuleGroup::Preview, rules::refurb::rules::RepeatedAppend),
+        (Refurb, "131") => (RuleGroup::Preview, rules::refurb::rules::DeleteFullSlice),
+        (Refurb, "132") => (RuleGroup::Preview, rules::refurb::rules::CheckAndRemoveFromSet),
 
         _ => return None,
     })

crates/ruff/src/rule_selector.rs

@@ -9,13 +9,14 @@ use crate::codes::RuleCodePrefix;
 use crate::codes::RuleIter;
 use crate::registry::{Linter, Rule, RuleNamespace};
 use crate::rule_redirects::get_redirect;
+use crate::settings::types::PreviewMode;
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum RuleSelector {
     /// Select all stable rules.
     All,
-    /// Select all nursery rules.
-    Nursery,
+    /// Category to select all preview rules, previously known as the nursery
+    Preview,
     /// Legacy category to select both the `mccabe` and `flake8-comprehensions` linters
     /// via a single selector.
     C,
@@ -29,6 +30,11 @@ pub enum RuleSelector {
         prefix: RuleCodePrefix,
         redirected_from: Option<&'static str>,
     },
+    /// Select an individual rule with a given prefix.
+    Rule {
+        prefix: RuleCodePrefix,
+        redirected_from: Option<&'static str>,
+    },
 }
 
 impl From<Linter> for RuleSelector {
@@ -43,7 +49,9 @@ impl FromStr for RuleSelector {
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         match s {
             "ALL" => Ok(Self::All),
-            "NURSERY" => Ok(Self::Nursery),
+            // Legacy support for selecting preview rules as "nursery"
+            "NURSERY" => Ok(Self::Preview),
+            "PREVIEW" => Ok(Self::Preview),
             "C" => Ok(Self::C),
             "T" => Ok(Self::T),
             _ => {
@@ -59,16 +67,42 @@ impl FromStr for RuleSelector {
                     return Ok(Self::Linter(linter));
                 }
 
-                Ok(Self::Prefix {
-                    prefix: RuleCodePrefix::parse(&linter, code)
-                        .map_err(|_| ParseError::Unknown(s.to_string()))?,
-                    redirected_from,
-                })
+                // Does the selector select a single rule?
+                let prefix = RuleCodePrefix::parse(&linter, code)
+                    .map_err(|_| ParseError::Unknown(s.to_string()))?;
+                if is_single_rule_selector(&prefix) {
+                    Ok(Self::Rule {
+                        prefix,
+                        redirected_from,
+                    })
+                } else {
+                    Ok(Self::Prefix {
+                        prefix,
+                        redirected_from,
+                    })
+                }
             }
         }
     }
 }
 
+/// Returns `true` if the [`RuleCodePrefix`] matches a single rule exactly
+/// (e.g., `E225`, as opposed to `E2`).
+fn is_single_rule_selector(prefix: &RuleCodePrefix) -> bool {
+    let mut rules = prefix.rules();
+
+    // The selector must match a single rule.
+    let Some(rule) = rules.next() else {
+        return false;
+    };
+    if rules.next().is_some() {
+        return false;
+    }
+
+    // The rule must match the selector exactly.
+    rule.noqa_code().suffix() == prefix.short_code()
+}
+
 #[derive(Debug, thiserror::Error)]
 pub enum ParseError {
     #[error("Unknown rule selector: `{0}`")]
@@ -81,10 +115,10 @@ impl RuleSelector {
     pub fn prefix_and_code(&self) -> (&'static str, &'static str) {
         match self {
             RuleSelector::All => ("", "ALL"),
-            RuleSelector::Nursery => ("", "NURSERY"),
+            RuleSelector::Preview => ("", "PREVIEW"),
             RuleSelector::C => ("", "C"),
             RuleSelector::T => ("", "T"),
-            RuleSelector::Prefix { prefix, .. } => {
+            RuleSelector::Prefix { prefix, .. } | RuleSelector::Rule { prefix, .. } => {
                 (prefix.linter().common_prefix(), prefix.short_code())
             }
             RuleSelector::Linter(l) => (l.common_prefix(), ""),
@@ -135,26 +169,13 @@ impl Visitor<'_> for SelectorVisitor {
     }
 }
 
-impl From<RuleCodePrefix> for RuleSelector {
-    fn from(prefix: RuleCodePrefix) -> Self {
-        Self::Prefix {
-            prefix,
-            redirected_from: None,
-        }
-    }
-}
-
-impl IntoIterator for &RuleSelector {
-    type IntoIter = RuleSelectorIter;
-    type Item = Rule;
-
-    fn into_iter(self) -> Self::IntoIter {
+impl RuleSelector {
+    /// Return all matching rules, regardless of whether they're in preview.
+    pub fn all_rules(&self) -> impl Iterator<Item = Rule> + '_ {
         match self {
-            RuleSelector::All => {
-                RuleSelectorIter::All(Rule::iter().filter(|rule| !rule.is_nursery()))
-            }
-            RuleSelector::Nursery => {
-                RuleSelectorIter::Nursery(Rule::iter().filter(Rule::is_nursery))
+            RuleSelector::All => RuleSelectorIter::All(Rule::iter()),
+            RuleSelector::Preview => {
+                RuleSelectorIter::Nursery(Rule::iter().filter(Rule::is_preview))
             }
             RuleSelector::C => RuleSelectorIter::Chain(
                 Linter::Flake8Comprehensions
@@ -167,13 +188,22 @@ impl IntoIterator for &RuleSelector {
                     .chain(Linter::Flake8Print.rules()),
             ),
             RuleSelector::Linter(linter) => RuleSelectorIter::Vec(linter.rules()),
-            RuleSelector::Prefix { prefix, .. } => RuleSelectorIter::Vec(prefix.clone().rules()),
+            RuleSelector::Prefix { prefix, .. } | RuleSelector::Rule { prefix, .. } => {
+                RuleSelectorIter::Vec(prefix.clone().rules())
+            }
         }
     }
+
+    /// Returns rules matching the selector, taking into account whether preview mode is enabled.
+    pub fn rules(&self, preview: PreviewMode) -> impl Iterator<Item = Rule> + '_ {
+        self.all_rules().filter(move |rule| {
+            matches!(self, RuleSelector::Rule { .. }) || preview.is_enabled() || !rule.is_preview()
+        })
+    }
 }
 
 pub enum RuleSelectorIter {
-    All(std::iter::Filter<RuleIter, fn(&Rule) -> bool>),
+    All(RuleIter),
     Nursery(std::iter::Filter<RuleIter, fn(&Rule) -> bool>),
     Chain(std::iter::Chain<std::vec::IntoIter<Rule>, std::vec::IntoIter<Rule>>),
     Vec(std::vec::IntoIter<Rule>),
@@ -266,18 +296,18 @@ impl RuleSelector {
     pub fn specificity(&self) -> Specificity {
         match self {
             RuleSelector::All => Specificity::All,
-            RuleSelector::Nursery => Specificity::All,
+            RuleSelector::Preview => Specificity::All,
             RuleSelector::T => Specificity::LinterGroup,
             RuleSelector::C => Specificity::LinterGroup,
             RuleSelector::Linter(..) => Specificity::Linter,
+            RuleSelector::Rule { .. } => Specificity::Rule,
             RuleSelector::Prefix { prefix, .. } => {
                 let prefix: &'static str = prefix.short_code();
                 match prefix.len() {
-                    1 => Specificity::Code1Char,
-                    2 => Specificity::Code2Chars,
-                    3 => Specificity::Code3Chars,
-                    4 => Specificity::Code4Chars,
-                    5 => Specificity::Code5Chars,
+                    1 => Specificity::Prefix1Char,
+                    2 => Specificity::Prefix2Chars,
+                    3 => Specificity::Prefix3Chars,
+                    4 => Specificity::Prefix4Chars,
                     _ => panic!("RuleSelector::specificity doesn't yet support codes with so many characters"),
                 }
             }
@@ -285,16 +315,24 @@ impl RuleSelector {
     }
 }
 
-#[derive(EnumIter, PartialEq, Eq, PartialOrd, Ord, Copy, Clone)]
+#[derive(EnumIter, PartialEq, Eq, PartialOrd, Ord, Copy, Clone, Debug)]
 pub enum Specificity {
+    /// The specificity when selecting all rules (e.g., `--select ALL`).
     All,
+    /// The specificity when selecting a linter group (e.g., `--select PL`).
     LinterGroup,
+    /// The specificity when selecting a linter (e.g., `--select PLE` or `--select UP`).
     Linter,
-    Code1Char,
-    Code2Chars,
-    Code3Chars,
-    Code4Chars,
-    Code5Chars,
+    /// The specificity when selecting via a rule prefix at one-character depth (e.g., `--select PLE1`).
+    Prefix1Char,
+    /// The specificity when selecting via a rule prefix at two-character depth (e.g., `--select PLE12`).
+    Prefix2Chars,
+    /// The specificity when selecting via a rule prefix at one-character depth (e.g., `--select PLE120`).
+    Prefix3Chars,
+    /// The specificity when selecting via a rule prefix at one-character depth (e.g., `--select PLE120`).
+    Prefix4Chars,
+    /// The specificity when selecting an individual rule (e.g., `--select PLE1205`).
+    Rule,
 }
 
 #[cfg(feature = "clap")]

crates/ruff/src/settings/defaults.rs

@@ -70,7 +70,10 @@ pub static INCLUDE: Lazy<Vec<FilePattern>> = Lazy::new(|| {
 impl Default for Settings {
     fn default() -> Self {
         Self {
-            rules: PREFIXES.iter().flat_map(IntoIterator::into_iter).collect(),
+            rules: PREFIXES
+                .iter()
+                .flat_map(|selector| selector.rules(PreviewMode::default()))
+                .collect(),
             allowed_confusables: FxHashSet::from_iter([]),
             builtins: vec![],
             dummy_variable_rgx: DUMMY_VARIABLE_RGX.clone(),

crates/ruff/src/settings/types.rs

@@ -194,7 +194,7 @@ pub struct PerFileIgnore {
 
 impl PerFileIgnore {
     pub fn new(pattern: String, prefixes: &[RuleSelector], project_root: Option<&Path>) -> Self {
-        let rules: RuleSet = prefixes.iter().flat_map(IntoIterator::into_iter).collect();
+        let rules: RuleSet = prefixes.iter().flat_map(RuleSelector::all_rules).collect();
         let path = Path::new(&pattern);
         let absolute = match project_root {
             Some(project_root) => fs::normalize_path_to(path, project_root),

crates/ruff_cli/src/commands/rule.rs

@@ -19,7 +19,7 @@ struct Explanation<'a> {
     message_formats: &'a [&'a str],
     autofix: String,
     explanation: Option<&'a str>,
-    nursery: bool,
+    preview: bool,
 }
 
 impl<'a> Explanation<'a> {
@@ -35,7 +35,7 @@ impl<'a> Explanation<'a> {
             message_formats: rule.message_formats(),
             autofix,
             explanation: rule.explanation(),
-            nursery: rule.is_nursery(),
+            preview: rule.is_preview(),
         }
     }
 }
@@ -58,11 +58,10 @@ fn format_rule_text(rule: Rule) -> String {
         output.push('\n');
     }
 
-    if rule.is_nursery() {
+    if rule.is_preview() {
         output.push_str(&format!(
-            r#"This rule is part of the **nursery**, a collection of newer lints that are
-still under development. As such, it must be enabled by explicitly selecting
-{}."#,
+            r#"This rule is in preview and is not stable. It may be enabled by explicitly selecting {}"
+" or providing the `--preview` flag."#,
             rule.noqa_code()
         ));
         output.push('\n');

crates/ruff_dev/src/generate_docs.rs

@@ -43,11 +43,10 @@ pub(crate) fn main(args: &Args) -> Result<()> {
                 output.push('\n');
             }
 
-            if rule.is_nursery() {
+            if rule.is_preview() {
                 output.push_str(&format!(
-                    r#"This rule is part of the **nursery**, a collection of newer lints that are
-still under development. As such, it must be enabled by explicitly selecting
-{}."#,
+                    r#"This rule is in preview and is not stable. It may be enabled by explicitly selecting {}"
+" or providing the `--preview` flag."#,
                     rule.noqa_code()
                 ));
                 output.push('\n');

crates/ruff_dev/src/generate_rules_table.rs

@@ -11,7 +11,7 @@ use ruff_diagnostics::AutofixKind;
 use ruff_workspace::options::Options;
 
 const FIX_SYMBOL: &str = "🛠";
-const NURSERY_SYMBOL: &str = "🌅";
+const PREVIEW_SYMBOL: &str = "🌅";
 
 fn generate_table(table_out: &mut String, rules: impl IntoIterator<Item = Rule>, linter: &Linter) {
     table_out.push_str("| Code | Name | Message | |");
@@ -25,12 +25,12 @@ fn generate_table(table_out: &mut String, rules: impl IntoIterator<Item = Rule>,
             }
             AutofixKind::None => format!("<span style='opacity: 0.1'>{FIX_SYMBOL}</span>"),
         };
-        let nursery_token = if rule.is_nursery() {
-            format!("<span style='opacity: 1'>{NURSERY_SYMBOL}</span>")
+        let preview_token = if rule.is_preview() {
+            format!("<span style='opacity: 1'>{PREVIEW_SYMBOL}</span>")
         } else {
-            format!("<span style='opacity: 0.1'>{NURSERY_SYMBOL}</span>")
+            format!("<span style='opacity: 0.1'>{PREVIEW_SYMBOL}</span>")
         };
-        let status_token = format!("{fix_token} {nursery_token}");
+        let status_token = format!("{fix_token} {preview_token}");
 
         let rule_name = rule.as_ref();
 
@@ -61,7 +61,7 @@ pub(crate) fn generate() -> String {
     table_out.push('\n');
 
     table_out.push_str(&format!(
-        "The {NURSERY_SYMBOL} emoji indicates that a rule is part of the [\"nursery\"](../faq/#what-is-the-nursery)."
+        "The {PREVIEW_SYMBOL} emoji indicates that a rule is part of the [\"nursery\"](../faq/#what-is-the-nursery)."
     ));
     table_out.push('\n');
     table_out.push('\n');

crates/ruff_macros/src/map_codes.rs

@@ -8,7 +8,7 @@ use syn::{
     Ident, ItemFn, LitStr, Pat, Path, Stmt, Token,
 };
 
-use crate::rule_code_prefix::{get_prefix_ident, if_all_same, is_nursery};
+use crate::rule_code_prefix::{get_prefix_ident, if_all_same};
 
 /// A rule entry in the big match statement such a
 /// `(Pycodestyle, "E112") => (RuleGroup::Nursery, rules::pycodestyle::rules::logical_lines::NoIndentedBlock),`
@@ -156,7 +156,7 @@ pub(crate) fn map_codes(func: &ItemFn) -> syn::Result<TokenStream> {
 
         output.extend(quote! {
             impl #linter {
-                pub fn rules(self) -> ::std::vec::IntoIter<Rule> {
+                pub fn rules(&self) -> ::std::vec::IntoIter<Rule> {
                     match self { #prefix_into_iter_match_arms }
                 }
             }
@@ -172,7 +172,7 @@ pub(crate) fn map_codes(func: &ItemFn) -> syn::Result<TokenStream> {
                 })
             }
 
-            pub fn rules(self) -> ::std::vec::IntoIter<Rule> {
+            pub fn rules(&self) -> ::std::vec::IntoIter<Rule> {
                 match self {
                     #(RuleCodePrefix::#linter_idents(prefix) => prefix.clone().rules(),)*
                 }
@@ -195,26 +195,12 @@ fn rules_by_prefix(
     // TODO(charlie): Why do we do this here _and_ in `rule_code_prefix::expand`?
     let mut rules_by_prefix = BTreeMap::new();
 
-    for (code, rule) in rules {
-        // Nursery rules have to be explicitly selected, so we ignore them when looking at
-        // prefix-level selectors (e.g., `--select SIM10`), but add the rule itself under
-        // its fully-qualified code (e.g., `--select SIM101`).
-        if is_nursery(&rule.group) {
-            rules_by_prefix.insert(code.clone(), vec![(rule.path.clone(), rule.attrs.clone())]);
-            continue;
-        }
-
+    for code in rules.keys() {
         for i in 1..=code.len() {
             let prefix = code[..i].to_string();
             let rules: Vec<_> = rules
                 .iter()
                 .filter_map(|(code, rule)| {
-                    // Nursery rules have to be explicitly selected, so we ignore them when
-                    // looking at prefixes.
-                    if is_nursery(&rule.group) {
-                        return None;
-                    }
-
                     if code.starts_with(&prefix) {
                         Some((rule.path.clone(), rule.attrs.clone()))
                     } else {
@@ -311,8 +297,8 @@ See also https://github.com/astral-sh/ruff/issues/2186.
                 }
             }
 
-            pub fn is_nursery(&self) -> bool {
-                matches!(self.group(), RuleGroup::Nursery)
+            pub fn is_preview(&self) -> bool {
+                matches!(self.group(), RuleGroup::Preview)
             }
         }
 
@@ -336,12 +322,10 @@ fn generate_iter_impl(
     let mut linter_rules_match_arms = quote!();
     let mut linter_all_rules_match_arms = quote!();
     for (linter, map) in linter_to_rules {
-        let rule_paths = map.values().filter(|rule| !is_nursery(&rule.group)).map(
-            |Rule { attrs, path, .. }| {
-                let rule_name = path.segments.last().unwrap();
-                quote!(#(#attrs)* Rule::#rule_name)
-            },
-        );
+        let rule_paths = map.values().map(|Rule { attrs, path, .. }| {
+            let rule_name = path.segments.last().unwrap();
+            quote!(#(#attrs)* Rule::#rule_name)
+        });
         linter_rules_match_arms.extend(quote! {
             Linter::#linter => vec![#(#rule_paths,)*].into_iter(),
         });

crates/ruff_macros/src/rule_code_prefix.rs

@@ -12,22 +12,14 @@ pub(crate) fn expand<'a>(
     let mut prefix_to_codes: BTreeMap<String, BTreeSet<String>> = BTreeMap::default();
     let mut code_to_attributes: BTreeMap<String, &[Attribute]> = BTreeMap::default();
 
-    for (variant, group, attr) in variants {
+    for (variant, .., attr) in variants {
         let code_str = variant.to_string();
-        // Nursery rules have to be explicitly selected, so we ignore them when looking at prefixes.
-        if is_nursery(group) {
+        for i in 1..=code_str.len() {
+            let prefix = code_str[..i].to_string();
             prefix_to_codes
-                .entry(code_str.clone())
+                .entry(prefix)
                 .or_default()
                 .insert(code_str.clone());
-        } else {
-            for i in 1..=code_str.len() {
-                let prefix = code_str[..i].to_string();
-                prefix_to_codes
-                    .entry(prefix)
-                    .or_default()
-                    .insert(code_str.clone());
-            }
         }
 
         code_to_attributes.insert(code_str, attr);
@@ -125,14 +117,3 @@ pub(crate) fn get_prefix_ident(prefix: &str) -> Ident {
     };
     Ident::new(&prefix, Span::call_site())
 }
-
-/// Returns true if the given group is the "nursery" group.
-pub(crate) fn is_nursery(group: &Path) -> bool {
-    let group = group
-        .segments
-        .iter()
-        .map(|segment| segment.ident.to_string())
-        .collect::<Vec<String>>()
-        .join("::");
-    group == "RuleGroup::Nursery"
-}

crates/ruff_workspace/src/configuration.rs

@@ -440,14 +440,18 @@ impl Configuration {
     }
 
     pub fn as_rule_table(&self) -> RuleTable {
+        let preview = self.preview.unwrap_or_default();
+
         // The select_set keeps track of which rules have been selected.
-        let mut select_set: RuleSet = defaults::PREFIXES.iter().flatten().collect();
-        // The fixable set keeps track of which rules are fixable.
-        let mut fixable_set: RuleSet = RuleSelector::All
-            .into_iter()
-            .chain(&RuleSelector::Nursery)
+        let mut select_set: RuleSet = defaults::PREFIXES
+            .iter()
+            .map(|selector| selector.rules(preview))
+            .flatten()
             .collect();
 
+        // The fixable set keeps track of which rules are fixable.
+        let mut fixable_set: RuleSet = RuleSelector::All.rules(preview).collect();
+
         // Ignores normally only subtract from the current set of selected
         // rules.  By that logic the ignore in `select = [], ignore = ["E501"]`
         // would be effectless. Instead we carry over the ignores to the next
@@ -482,7 +486,7 @@ impl Configuration {
                     .chain(selection.extend_select.iter())
                     .filter(|s| s.specificity() == spec)
                 {
-                    for rule in selector {
+                    for rule in selector.rules(preview) {
                         select_map_updates.insert(rule, true);
                     }
                 }
@@ -492,7 +496,7 @@ impl Configuration {
                     .chain(carriedover_ignores.into_iter().flatten())
                     .filter(|s| s.specificity() == spec)
                 {
-                    for rule in selector {
+                    for rule in selector.rules(preview) {
                         select_map_updates.insert(rule, false);
                     }
                 }
@@ -504,7 +508,7 @@ impl Configuration {
                     .chain(selection.extend_fixable.iter())
                     .filter(|s| s.specificity() == spec)
                 {
-                    for rule in selector {
+                    for rule in selector.rules(preview) {
                         fixable_map_updates.insert(rule, true);
                     }
                 }
@@ -514,7 +518,7 @@ impl Configuration {
                     .chain(carriedover_unfixables.into_iter().flatten())
                     .filter(|s| s.specificity() == spec)
                 {
-                    for rule in selector {
+                    for rule in selector.rules(preview) {
                         fixable_map_updates.insert(rule, false);
                     }
                 }

docs/faq.md

@@ -382,13 +382,13 @@ matter how they're provided, which avoids accidental incompatibilities and simpl
 By default, no `convention` is set, and so the enabled rules are determined by the `select` setting
 alone.
 
-## What is the "nursery"?
+## What is preview mode?
 
-The "nursery" is a collection of newer rules that are considered experimental or unstable.
+Preview mode enables a collection of newer rules and fixes that are considered experimental or unstable.
 
-If a rule is marked as part of the "nursery", it can only be enabled via direct selection. For
-example, consider a hypothetical rule, `HYP001`. If `HYP001` were included in the "nursery", it
-could be enabled by adding the following to your `pyproject.toml`:
+If a rule is marked as preview, it can only be enabled via direct selection or the `--preview` flag. For
+example, consider a hypothetical rule, `HYP001`. If `HYP001` were in preview, it could be enabled by adding the 
+following to your `pyproject.toml`:
 
 ```toml
 [tool.ruff]
@@ -409,10 +409,15 @@ Similarly, it would _not_ be enabled via the `ALL` selector:
 select = ["ALL"]
 ```
 
-(The "nursery" terminology comes from [Clippy](https://doc.rust-lang.org/nightly/clippy/), a similar
-tool for linting Rust code.)
+Unless you also enabled `preview`:
 
-To see which rules are currently in the "nursery", visit the [rules reference](https://beta.ruff.rs/docs/rules/).
+```toml
+[tool.ruff]
+select = ["ALL"]
+preview = true
+```
+
+To see which rules are currently in preview, visit the [rules reference](https://beta.ruff.rs/docs/rules/).
 
 ## How can I tell what settings Ruff is using to check my code?
 

ruff.schema.json

@@ -1797,6 +1797,8 @@
         "COM818",
         "COM819",
         "CPY",
+        "CPY0",
+        "CPY00",
         "CPY001",
         "D",
         "D1",
@@ -1883,6 +1885,7 @@
         "E1",
         "E10",
         "E101",
+        "E11",
         "E111",
         "E112",
         "E113",
@@ -1890,10 +1893,14 @@
         "E115",
         "E116",
         "E117",
+        "E2",
+        "E20",
         "E201",
         "E202",
         "E203",
+        "E21",
         "E211",
+        "E22",
         "E221",
         "E222",
         "E223",
@@ -1902,15 +1909,20 @@
         "E226",
         "E227",
         "E228",
+        "E23",
         "E231",
+        "E24",
         "E241",
         "E242",
+        "E25",
         "E251",
         "E252",
+        "E26",
         "E261",
         "E262",
         "E265",
         "E266",
+        "E27",
         "E271",
         "E272",
         "E273",
@@ -2051,7 +2063,10 @@
         "FLY00",
         "FLY002",
         "FURB",
+        "FURB1",
+        "FURB11",
         "FURB113",
+        "FURB13",
         "FURB131",
         "FURB132",
         "G",
@@ -2196,6 +2211,9 @@
         "PLC04",
         "PLC041",
         "PLC0414",
+        "PLC1",
+        "PLC19",
+        "PLC190",
         "PLC1901",
         "PLC3",
         "PLC30",
@@ -2288,6 +2306,9 @@
         "PLR55",
         "PLR550",
         "PLR5501",
+        "PLR6",
+        "PLR63",
+        "PLR630",
         "PLR6301",
         "PLW",
         "PLW0",
@@ -2315,12 +2336,16 @@
         "PLW1509",
         "PLW151",
         "PLW1510",
+        "PLW16",
+        "PLW164",
         "PLW1641",
         "PLW2",
         "PLW29",
         "PLW290",
         "PLW2901",
         "PLW3",
+        "PLW32",
+        "PLW320",
         "PLW3201",
         "PLW33",
         "PLW330",