perf(linter): avoid unnecessary work in nextjs:no_duplicate_head ru…

…le (#4465) In `nextjs:no_duplicate_head` rule, avoid allocating a `Vec` unless more than one `<Head>` is found (uncommon case). Also, #4464 made getting span of a `Reference` a little more expensive. Avoid this work unless it's needed (which it generally won't be).
oxc-project · Jul 26, 2024 · 81384f5 · 81384f5
1 parent 348c1ad
commit 81384f5
Showing 1 changed file with 40 additions and 12 deletions.
diff --git a/crates/oxc_linter/src/rules/nextjs/no_duplicate_head.rs b/crates/oxc_linter/src/rules/nextjs/no_duplicate_head.rs
@@ -1,6 +1,7 @@
 use oxc_ast::AstKind;
 use oxc_diagnostics::{LabeledSpan, OxcDiagnostic};
 use oxc_macros::declare_oxc_lint;
+use oxc_span::GetSpan;
 
 use crate::{context::LintContext, rule::Rule};
 
@@ -56,19 +57,46 @@ impl Rule for NoDuplicateHead {
             return;
         }
 
+        // 1 x `<Head>` is fine, more than 1 is not.
+        // Avoid allocating a `Vec`, or looking up span in common case
+        // where only a single `<Head>` is found.
+        let mut first_node_id = None;
+        let mut labels = vec![];
         let nodes = ctx.nodes();
-        let labels = symbols
-            .get_resolved_references(symbol_id)
-            .filter(|r| r.is_read())
-            .filter(|r| {
-                let kind = nodes.ancestors(r.node_id()).nth(2).map(|node_id| nodes.kind(node_id));
-                matches!(kind, Some(AstKind::JSXOpeningElement(_)))
-            })
-            .map(|reference| ctx.semantic().reference_span(reference))
-            .map(LabeledSpan::underline)
-            .collect::<Vec<_>>();
-
-        if labels.len() <= 1 {
+        let get_label = |node_id| {
+            let span = nodes.kind(node_id).span();
+            LabeledSpan::underline(span)
+        };
+
+        for reference in symbols.get_resolved_references(symbol_id) {
+            if !reference.is_read() {
+                continue;
+            }
+
+            if !matches!(
+                nodes.ancestors(reference.node_id()).nth(2).map(|node_id| nodes.kind(node_id)),
+                Some(AstKind::JSXOpeningElement(_))
+            ) {
+                continue;
+            }
+
+            let node_id = reference.node_id();
+            #[allow(clippy::unnecessary_unwrap)]
+            if first_node_id.is_none() {
+                // First `<Head>` found
+                first_node_id = Some(node_id);
+            } else if labels.is_empty() {
+                // 2nd `<Head>` found - populate `labels` with both
+                let first_node_id = first_node_id.unwrap();
+                labels.extend([get_label(first_node_id), get_label(node_id)]);
+            } else {
+                // Further `<Head>` found - add to `node_ids`
+                labels.push(get_label(node_id));
+            }
+        }
+
+        // `labels` is empty if 0 or 1 `<Head>` found
+        if labels.is_empty() {
             return;
         }