fix(linter): rule and generic filters do not re-configure existing rules

Continuation of #6085.

crates/oxc_linter/src/builder.rs

@@ -156,44 +156,18 @@ impl LinterBuilder {
 
     pub fn with_filter(mut self, filter: LintFilter) -> Self {
         let (severity, filter) = filter.into();
-        let all_rules = self.cache.borrow();
 
         match severity {
             AllowWarnDeny::Deny | AllowWarnDeny::Warn => match filter {
                 LintFilterKind::Category(category) => {
-                    let rules_to_configure = all_rules.iter().filter(|r| r.category() == category);
-                    for rule in rules_to_configure {
-                        if let Some(mut existing_rule) = self.rules.take(rule) {
-                            existing_rule.severity = severity;
-                            self.rules.insert(existing_rule);
-                        } else {
-                            self.rules.insert(RuleWithSeverity::new(rule.clone(), severity));
-                        }
-                    }
-                }
-                LintFilterKind::Rule(_, name) => {
-                    self.rules.extend(
-                        all_rules
-                            .iter()
-                            .filter(|rule| rule.name() == name)
-                            .map(|rule| RuleWithSeverity::new(rule.clone(), severity)),
-                    );
+                    self.upsert_where(severity, |r| r.category() == category);
                 }
+                LintFilterKind::Rule(_, name) => self.upsert_where(severity, |r| r.name() == name),
                 LintFilterKind::Generic(name_or_category) => {
                     if name_or_category == "all" {
-                        self.rules.extend(
-                            all_rules
-                                .iter()
-                                .filter(|rule| rule.category() != RuleCategory::Nursery)
-                                .map(|rule| RuleWithSeverity::new(rule.clone(), severity)),
-                        );
+                        self.upsert_where(severity, |r| r.category() != RuleCategory::Nursery);
                     } else {
-                        self.rules.extend(
-                            all_rules
-                                .iter()
-                                .filter(|rule| rule.name() == name_or_category)
-                                .map(|rule| RuleWithSeverity::new(rule.clone(), severity)),
-                        );
+                        self.upsert_where(severity, |r| r.name() == name_or_category);
                     }
                 }
             },
@@ -213,11 +187,30 @@ impl LinterBuilder {
                 }
             },
         }
-        drop(all_rules);
 
         self
     }
 
+    /// Warn/Deny a let of rules based on some predicate. Rules already in `self.rules` get
+    /// re-configured, while those that are not are added. Affects rules where `query` returns
+    /// `true`.
+    fn upsert_where<F>(&mut self, severity: AllowWarnDeny, query: F)
+    where
+        F: Fn(&&RuleEnum) -> bool,
+    {
+        let all_rules = self.cache.borrow();
+        // NOTE: we may want to warn users if they're configuring a rule that does not exist.
+        let rules_to_configure = all_rules.iter().filter(query);
+        for rule in rules_to_configure {
+            if let Some(mut existing_rule) = self.rules.take(rule) {
+                existing_rule.severity = severity;
+                self.rules.insert(existing_rule);
+            } else {
+                self.rules.insert(RuleWithSeverity::new(rule.clone(), severity));
+            }
+        }
+    }
+
     #[must_use]
     pub fn build(self) -> Linter {
         // When a plugin gets disabled before build(), rules for that plugin aren't removed until
@@ -403,6 +396,26 @@ mod test {
         }
     }
 
+    #[test]
+    fn test_filter_deny_single_rule_on_default() {
+        let builder = LinterBuilder::default();
+        let initial_rule_count = builder.rules.len();
+
+        let builder =
+            builder.with_filters([
+                LintFilter::new(AllowWarnDeny::Deny, "eslint/no-const-assign").unwrap()
+            ]);
+        let rule_count_after_deny = builder.rules.len();
+        assert_eq!(initial_rule_count, rule_count_after_deny, "Changing a single rule from warn to deny should not add a new one, just modify what's already there.");
+
+        let no_const_assign = builder
+            .rules
+            .iter()
+            .find(|r| r.plugin_name() == "eslint" && r.name() == "no-const-assign")
+            .expect("Could not find eslint/no-const-assign after configuring it to 'deny'");
+        assert_eq!(no_const_assign.severity, AllowWarnDeny::Deny);
+    }
+
     #[test]
     fn test_filter_allow_all_then_warn() {
         let builder =