perf(linter): reduce rule config dispatch size (#25461)

Generate `from_configuration` match arms only for the 341 rules that override the default implementation. The other 508 rules clone their default value from `RULES`.

This reduces the release oxlint binary from 13,963,312 to 13,946,800 bytes (-16,512 bytes).

AI-assisted.

tasks/linter_codegen/src/main.rs

@@ -128,7 +128,18 @@ pub fn generate_rules_enum_file() -> io::Result<()> {
         .map_err(|e| std::io::Error::other(format!("could not find project root: {e}")))?;
 
     let rules_file_contents = fs::read_to_string(root.join("crates/oxc_linter/src/rules.rs"))?;
-    let rule_entries = get_all_rules(&rules_file_contents);
+    let mut rule_entries = get_all_rules(&rules_file_contents);
+
+    for rule in &mut rule_entries {
+        let Some(path) = find_rule_source_file(&root, rule) else { continue };
+        let Ok(source) = fs::read_to_string(path) else { continue };
+        let Ok(file) = syn::parse_file(&source) else { continue };
+        let Some(rule_impl) = find_rule_impl_block(&file, &rule.rule_struct_name()) else {
+            continue;
+        };
+        rule.has_custom_from_configuration =
+            find_impl_function(rule_impl, "from_configuration").is_some();
+    }
 
     let out = rules_enum::generate_rules_enum(&rule_entries);
     let formatted_out = rust_fmt(&out);

tasks/linter_codegen/src/rules.rs

@@ -9,6 +9,8 @@ pub struct RuleEntry<'e> {
     pub plugin_module_name: &'e str,
     /// The rule's module name, like `no_debugger` in `eslint::no_debugger:NoDebugger`.
     pub rule_module_name: &'e str,
+    /// Whether the rule overrides `Rule::from_configuration`.
+    pub has_custom_from_configuration: bool,
 }
 
 impl RuleEntry<'_> {
@@ -48,8 +50,13 @@ pub fn get_all_rules(contents: &str) -> Vec<RuleEntry<'_>> {
             && line.ends_with(';')
             && let Some(rule_name) = line.strip_prefix("pub mod ").and_then(|s| s.strip_suffix(';'))
         {
-            rule_entries
-                .push(RuleEntry { plugin_module_name: plugin, rule_module_name: rule_name });
+            rule_entries.push(RuleEntry {
+                plugin_module_name: plugin,
+                rule_module_name: rule_name,
+                // Preserve the existing generated behavior unless codegen confirms that the rule
+                // uses the default implementation.
+                has_custom_from_configuration: true,
+            });
         }
     }
 

tasks/linter_codegen/src/rules_enum.rs

@@ -200,6 +200,7 @@ fn generate_rule_enum_impl(rule_entries: &[RuleEntry<'_>]) -> TokenStream {
 
     let from_configuration_arms: Vec<TokenStream> = rule_entries
         .iter()
+        .filter(|rule| rule.has_custom_from_configuration)
         .map(|rule| {
             let enum_name = make_enum_ident(rule);
             quote! { Self::#enum_name(_) => Ok(Self::#enum_name(#enum_name::from_configuration(value)?)) }
@@ -345,7 +346,8 @@ fn generate_rule_enum_impl(rule_entries: &[RuleEntry<'_>]) -> TokenStream {
 
             pub fn from_configuration(&self, value: serde_json::Value) -> Result<Self, serde_json::error::Error> {
                 match self {
-                    #(#from_configuration_arms),*
+                    #(#from_configuration_arms,)*
+                    _ => Ok(RULES[self.id()].clone()),
                 }
             }