Turbopack: skip codegen effects when tracing

Author: mischnic

turbopack/crates/turbopack-ecmascript/benches/analyzer.rs

@@ -64,7 +64,7 @@ pub fn benchmark(c: &mut Criterion) {
                     None,
                     None,
                 );
-                let var_graph = create_graph(&program, &eval_context);
+                let var_graph = create_graph(&program, &eval_context, false);
 
                 let input = BenchInput {
                     program,
@@ -90,7 +90,7 @@ struct BenchInput {
 }
 
 fn bench_create_graph(b: &mut Bencher, input: &BenchInput) {
-    b.iter(|| create_graph(&input.program, &input.eval_context));
+    b.iter(|| create_graph(&input.program, &input.eval_context, false));
 }
 
 fn bench_link(b: &mut Bencher, input: &BenchInput) {

turbopack/crates/turbopack-ecmascript/benches/mod.rs

@@ -3,8 +3,8 @@ extern crate turbo_tasks_malloc;
 use criterion::{criterion_group, criterion_main};
 
 mod analyzer;
-mod full;
+mod references;
 
 criterion_group!(analyzer_benches, analyzer::benchmark);
-criterion_group!(full_benches, full::benchmark);
+criterion_group!(full_benches, references::benchmark);
 criterion_main!(analyzer_benches, full_benches);

turbopack/crates/turbopack-ecmascript/benches/full.rs renamed to turbopack/crates/turbopack-ecmascript/benches/references.rs

@@ -53,9 +53,11 @@ pub fn benchmark(c: &mut Criterion) {
             .resolved_cell();
 
             let mut cases = vec![];
-            for file in [
-                r#"packages/next/dist/compiled/babel-packages/packages-bundle.js"#,
-                r#"node_modules/.pnpm/react-dom@19.2.0-canary-03fda05d-20250820_react@19.2.0-canary-03fda05d-20250820/node_modules/react-dom/cjs/react-dom-client.development.js"#,
+            for (file, is_tracing) in [
+                (r#"packages/next/dist/compiled/babel-packages/packages-bundle.js"#, false),
+                (r#"packages/next/dist/compiled/babel-packages/packages-bundle.js"#, true),
+                (r#"node_modules/.pnpm/react-dom@19.2.0-canary-03fda05d-20250820_react@19.2.0-canary-03fda05d-20250820/node_modules/react-dom/cjs/react-dom-client.development.js"#, false),
+                (r#"node_modules/.pnpm/react-dom@19.2.0-canary-03fda05d-20250820_react@19.2.0-canary-03fda05d-20250820/node_modules/react-dom/cjs/react-dom-client.development.js"#, true),
             ] {
                 let module = EcmascriptModuleAsset::builder(
                     ResolvedVc::upcast(
@@ -67,6 +69,7 @@ pub fn benchmark(c: &mut Criterion) {
                     EcmascriptInputTransforms::empty().to_resolved().await?,
                     EcmascriptOptions {
                         tree_shaking_mode: Some(TreeShakingMode::ReexportsOnly),
+                        is_tracing,
                         ..Default::default()
                     }
                     .resolved_cell(),
@@ -76,21 +79,21 @@ pub fn benchmark(c: &mut Criterion) {
                 .to_resolved()
                 .await?;
 
-                cases.push((file, module));
+                cases.push((file.rsplit("/").next().unwrap(), if is_tracing { "tracing" } else { "full" }, module));
             }
             anyhow::Ok(cases)
         }))
         .unwrap();
 
-    let mut group = c.benchmark_group("full");
+    let mut group = c.benchmark_group("references");
     group.warm_up_time(Duration::from_secs(1));
-    group.measurement_time(Duration::from_secs(20));
+    group.measurement_time(Duration::from_secs(10));
 
-    for case in cases {
+    for (file, param, module) in cases {
         group.bench_with_input(
-            BenchmarkId::new("full", case.0),
+            BenchmarkId::new(file, param),
             &BenchInput {
-                module: case.1,
+                module,
                 storage: tt.clone(),
             },
             bench_full,

turbopack/crates/turbopack-ecmascript/src/analyzer/graph.rs

@@ -274,7 +274,7 @@ impl VarGraph {
 
 /// You should use same [Mark] for this function and
 /// [swc_ecma_transforms_base::resolver::resolver_with_mark]
-pub fn create_graph(m: &Program, eval_context: &EvalContext) -> VarGraph {
+pub fn create_graph(m: &Program, eval_context: &EvalContext, is_tracing: bool) -> VarGraph {
     let mut graph = VarGraph {
         values: Default::default(),
         free_var_ids: Default::default(),
@@ -283,6 +283,7 @@ pub fn create_graph(m: &Program, eval_context: &EvalContext) -> VarGraph {
 
     m.visit_with_ast_path(
         &mut Analyzer {
+            is_tracing,
             data: &mut graph,
             state: analyzer_state::AnalyzerState::new(),
             eval_context,
@@ -788,6 +789,8 @@ pub fn as_parent_path_skip(
 }
 
 struct Analyzer<'a> {
+    is_tracing: bool,
+
     data: &'a mut VarGraph,
     state: analyzer_state::AnalyzerState,
 
@@ -1274,6 +1277,10 @@ impl Analyzer<'_> {
         member_expr: &'ast MemberExpr,
         ast_path: &AstNodePath<AstParentNodeRef<'r>>,
     ) {
+        if self.is_tracing {
+            return;
+        }
+
         let obj_value = Box::new(self.eval_context.eval(&member_expr.obj));
         let prop_value = match &member_expr.prop {
             // TODO avoid clone
@@ -1315,7 +1322,9 @@ impl Analyzer<'_> {
                     start_ast_path,
                 } => {
                     self.effects = prev_effects;
-                    self.effects.push(Effect::Unreachable { start_ast_path });
+                    if !self.is_tracing {
+                        self.effects.push(Effect::Unreachable { start_ast_path });
+                    }
                     always_returns = true;
                 }
                 EarlyReturn::Conditional {
@@ -2008,7 +2017,7 @@ impl VisitAstPath for Analyzer<'_> {
         }
 
         // If this variable is unresolved, track it as a free (unbound) variable
-        if is_unresolved(ident, self.eval_context.unresolved_mark)
+        if !self.is_tracing && is_unresolved(ident, self.eval_context.unresolved_mark)
             || self.eval_context.force_free_values.contains(&ident.to_id())
         {
             self.add_effect(Effect::FreeVar {
@@ -2043,13 +2052,16 @@ impl VisitAstPath for Analyzer<'_> {
             // We are in some scope that will rebind this
             return;
         }
-        // Otherwise 'this' is free
-        self.add_effect(Effect::FreeVar {
-            var: atom!("this"),
-            ast_path: as_parent_path(ast_path),
-            span: node.span(),
-            in_try: is_in_try(ast_path),
-        })
+
+        if !self.is_tracing {
+            // Otherwise 'this' is free
+            self.add_effect(Effect::FreeVar {
+                var: atom!("this"),
+                ast_path: as_parent_path(ast_path),
+                span: node.span(),
+                in_try: is_in_try(ast_path),
+            })
+        }
     }
 
     fn visit_meta_prop_expr<'ast: 'r, 'r>(
@@ -2292,8 +2304,9 @@ impl VisitAstPath for Analyzer<'_> {
         n: &'ast UnaryExpr,
         ast_path: &mut swc_core::ecma::visit::AstNodePath<'r>,
     ) {
-        if n.op == UnaryOp::TypeOf {
+        if n.op == UnaryOp::TypeOf && !self.is_tracing {
             let arg_value = Box::new(self.eval_context.eval(&n.arg));
+
             self.add_effect(Effect::TypeOf {
                 arg: arg_value,
                 ast_path: as_parent_path(ast_path),
@@ -2414,7 +2427,10 @@ impl Analyzer<'_> {
                     (Some(then), Some(r#else)) => ConditionalKind::IfElse { then, r#else },
                     (Some(then), None) => ConditionalKind::If { then },
                     (None, Some(r#else)) => ConditionalKind::Else { r#else },
-                    (None, None) => unreachable!(),
+                    (None, None) => {
+                        // No effects, ignore
+                        return;
+                    }
                 };
                 self.add_effect(Effect::Conditional {
                     condition,

turbopack/crates/turbopack-ecmascript/src/analyzer/mod.rs

@@ -3828,7 +3828,7 @@ mod tests {
                     None,
                 );
 
-                let mut var_graph = create_graph(&m, &eval_context);
+                let mut var_graph = create_graph(&m, &eval_context, false);
                 let var_cache = Default::default();
 
                 let mut named_values = var_graph

turbopack/crates/turbopack-ecmascript/src/lib.rs

@@ -200,6 +200,9 @@ pub struct EcmascriptOptions {
     /// parsing fails. This is useful to keep the module graph structure intact when syntax errors
     /// are temporarily introduced.
     pub keep_last_successful_parse: bool,
+    /// Whether the modules in this context are never chunked/codegen-ed, but only used for
+    /// tracing.
+    pub is_tracing: bool,
 }
 
 #[turbo_tasks::value]