Allow overriding pydocstyle convention rules (#8586)

## Summary

This fixes #2606 by moving where we apply the convention ignores --
instead of applying that at the very end, e track, we now track which
rules have been specifically enabled (via `Specificity::Rule`). If they
have, then we do *not* apply the docstring overrides at the end.

## Test Plan

Added unit tests to `ruff_workspace` and an integration test to
`ruff_cli`

crates/ruff_workspace/src/configuration.rs

@@ -705,6 +705,10 @@ impl LintConfiguration {
         let mut deprecated_nursery_selectors = FxHashSet::default();
         let mut ignored_preview_selectors = FxHashSet::default();
 
+        // Track which docstring rules are specifically enabled
+        // which lets us override the docstring convention ignore-list
+        let mut docstring_overrides: FxHashSet<Rule> = FxHashSet::default();
+
         for selection in &self.rule_selections {
             // If a selection only specifies extend-select we cannot directly
             // apply its rule selectors to the select_set because we firstly have
@@ -716,6 +720,8 @@ impl LintConfiguration {
             let mut select_map_updates: FxHashMap<Rule, bool> = FxHashMap::default();
             let mut fixable_map_updates: FxHashMap<Rule, bool> = FxHashMap::default();
 
+            let mut docstring_override_updates: FxHashSet<Rule> = FxHashSet::default();
+
             let carriedover_ignores = carryover_ignores.take();
             let carriedover_unfixables = carryover_unfixables.take();
 
@@ -730,6 +736,10 @@ impl LintConfiguration {
                 {
                     for rule in selector.rules(&preview) {
                         select_map_updates.insert(rule, true);
+
+                        if spec == Specificity::Rule {
+                            docstring_override_updates.insert(rule);
+                        }
                     }
                 }
                 for selector in selection
@@ -742,6 +752,7 @@ impl LintConfiguration {
                         select_map_updates.insert(rule, false);
                     }
                 }
+
                 // Apply the same logic to `fixable` and `unfixable`.
                 for selector in selection
                     .fixable
@@ -780,6 +791,8 @@ impl LintConfiguration {
                 {
                     carryover_ignores = Some(&selection.ignore);
                 }
+
+                docstring_overrides = docstring_override_updates;
             } else {
                 // Otherwise we apply the updates on top of the existing select_set.
                 for (rule, enabled) in select_map_updates {
@@ -789,6 +802,10 @@ impl LintConfiguration {
                         select_set.remove(rule);
                     }
                 }
+
+                for rule in docstring_override_updates {
+                    docstring_overrides.insert(rule);
+                }
             }
 
             // Apply the same logic to `fixable` and `unfixable`.
@@ -881,15 +898,17 @@ impl LintConfiguration {
             rules.enable(rule, fix);
         }
 
-        // If a docstring convention is specified, force-disable any incompatible error
-        // codes.
+        // If a docstring convention is specified, disable any incompatible error
+        // codes unless we are specifically overridden.
         if let Some(convention) = self
             .pydocstyle
             .as_ref()
             .and_then(|pydocstyle| pydocstyle.convention)
         {
             for rule in convention.rules_to_be_ignored() {
-                rules.disable(*rule);
+                if !docstring_overrides.contains(rule) {
+                    rules.disable(*rule);
+                }
             }
         }
 
@@ -1073,11 +1092,13 @@ pub fn resolve_src(src: &[String], project_root: &Path) -> Result<Vec<PathBuf>>
 #[cfg(test)]
 mod tests {
     use crate::configuration::{LintConfiguration, RuleSelection};
+    use crate::options::PydocstyleOptions;
     use ruff_linter::codes::{Flake8Copyright, Pycodestyle, Refurb};
     use ruff_linter::registry::{Linter, Rule, RuleSet};
     use ruff_linter::rule_selector::PreviewOptions;
     use ruff_linter::settings::types::PreviewMode;
     use ruff_linter::RuleSelector;
+    use std::str::FromStr;
 
     const NURSERY_RULES: &[Rule] = &[
         Rule::MissingCopyrightNotice,
@@ -1569,4 +1590,90 @@ mod tests {
         let expected = RuleSet::from_rules(NURSERY_RULES);
         assert_eq!(actual, expected);
     }
+
+    #[test]
+    fn select_docstring_convention_override() {
+        fn assert_override(rule_selections: Vec<RuleSelection>, should_be_overridden: bool) {
+            use ruff_linter::rules::pydocstyle::settings::Convention;
+
+            let config = LintConfiguration {
+                rule_selections,
+                pydocstyle: Some(PydocstyleOptions {
+                    convention: Some(Convention::Numpy),
+                    ..PydocstyleOptions::default()
+                }),
+                ..LintConfiguration::default()
+            };
+
+            let mut expected = RuleSet::from_rules(&[
+                Rule::from_code("D410").unwrap(),
+                Rule::from_code("D411").unwrap(),
+                Rule::from_code("D412").unwrap(),
+                Rule::from_code("D414").unwrap(),
+                Rule::from_code("D418").unwrap(),
+                Rule::from_code("D419").unwrap(),
+            ]);
+            if should_be_overridden {
+                expected.insert(Rule::from_code("D417").unwrap());
+            }
+            assert_eq!(
+                config
+                    .as_rule_table(PreviewMode::Disabled)
+                    .iter_enabled()
+                    .collect::<RuleSet>(),
+                expected,
+            );
+        }
+
+        let d41 = RuleSelector::from_str("D41").unwrap();
+        let d417 = RuleSelector::from_str("D417").unwrap();
+
+        // D417 does not appear when D41 is provided...
+        assert_override(
+            vec![RuleSelection {
+                select: Some(vec![d41.clone()]),
+                ..RuleSelection::default()
+            }],
+            false,
+        );
+
+        // ...but does appear when specified directly.
+        assert_override(
+            vec![RuleSelection {
+                select: Some(vec![d41.clone(), d417.clone()]),
+                ..RuleSelection::default()
+            }],
+            true,
+        );
+
+        // ...but disappears if there's a subsequent `--select`.
+        assert_override(
+            vec![
+                RuleSelection {
+                    select: Some(vec![d417.clone()]),
+                    ..RuleSelection::default()
+                },
+                RuleSelection {
+                    select: Some(vec![d41.clone()]),
+                    ..RuleSelection::default()
+                },
+            ],
+            false,
+        );
+
+        // ...although an `--extend-select` is fine.
+        assert_override(
+            vec![
+                RuleSelection {
+                    select: Some(vec![d417.clone()]),
+                    ..RuleSelection::default()
+                },
+                RuleSelection {
+                    extend_select: vec![d41.clone()],
+                    ..RuleSelection::default()
+                },
+            ],
+            true,
+        );
+    }
 }

crates/ruff_workspace/src/options.rs

@@ -2405,9 +2405,18 @@ pub struct PydocstyleOptions {
     /// convention = "google"
     /// ```
     ///
-    /// As conventions force-disable all rules not included in the convention,
-    /// enabling _additional_ rules on top of a convention is currently
-    /// unsupported.
+    /// To modify a convention (i.e., to enable an additional rule that's excluded
+    /// from the convention by default), select the desired rule via its fully
+    /// qualified rule code (e.g., `D400` instead of `D4` or `D40`):
+    ///
+    /// ```toml
+    /// [tool.ruff.lint]
+    /// # Enable D400 on top of the Google convention.
+    /// extend-select = ["D400"]
+    ///
+    /// [tool.ruff.lint.pydocstyle]
+    /// convention = "google"
+    /// ```
     #[option(
         default = r#"null"#,
         value_type = r#""google" | "numpy" | "pep257""#,