feat: Enable tree shaking in next.js (vercel/turborepo#8755)

crates/turbopack-ecmascript/benches/analyzer.rs

@@ -56,7 +56,7 @@ pub fn benchmark(c: &mut Criterion) {
                 program.visit_mut_with(&mut resolver(unresolved_mark, top_level_mark, false));
 
                 let eval_context =
-                    EvalContext::new(&program, unresolved_mark, top_level_mark, false, None);
+                    EvalContext::new(&program, unresolved_mark, top_level_mark, None);
                 let var_graph = create_graph(&program, &eval_context);
 
                 let input = BenchInput {

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

@@ -270,13 +270,12 @@ impl EvalContext {
         module: &Program,
         unresolved_mark: Mark,
         top_level_mark: Mark,
-        skip_namespace: bool,
         source: Option<Vc<Box<dyn Source>>>,
     ) -> Self {
         Self {
             unresolved_mark,
             top_level_mark,
-            imports: ImportMap::analyze(module, skip_namespace, source),
+            imports: ImportMap::analyze(module, source),
         }
     }
 

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

@@ -139,8 +139,6 @@ pub(crate) struct ImportMap {
 pub(crate) enum ImportedSymbol {
     ModuleEvaluation,
     Symbol(JsWord),
-    /// User requested the whole module
-    Namespace,
     Exports,
     Part(u32),
 }
@@ -202,16 +200,11 @@ impl ImportMap {
     }
 
     /// Analyze ES import
-    pub(super) fn analyze(
-        m: &Program,
-        skip_namespace: bool,
-        source: Option<Vc<Box<dyn Source>>>,
-    ) -> Self {
+    pub(super) fn analyze(m: &Program, source: Option<Vc<Box<dyn Source>>>) -> Self {
         let mut data = ImportMap::default();
 
         m.visit_with(&mut Analyzer {
             data: &mut data,
-            skip_namespace,
             source,
         });
 
@@ -221,7 +214,6 @@ impl ImportMap {
 
 struct Analyzer<'a> {
     data: &'a mut ImportMap,
-    skip_namespace: bool,
     source: Option<Vc<Box<dyn Source>>>,
 }
 
@@ -233,10 +225,6 @@ impl<'a> Analyzer<'a> {
         imported_symbol: ImportedSymbol,
         annotations: ImportAnnotations,
     ) -> Option<usize> {
-        if self.skip_namespace && matches!(imported_symbol, ImportedSymbol::Namespace) {
-            return None;
-        }
-
         let issue_source = self
             .source
             .map(|s| IssueSource::from_swc_offsets(s, span.lo.to_usize(), span.hi.to_usize()));
@@ -339,7 +327,7 @@ impl Visit for Analyzer<'_> {
         let i = self.ensure_reference(
             export.span,
             export.src.value.clone(),
-            symbol.unwrap_or(ImportedSymbol::Namespace),
+            symbol.unwrap_or(ImportedSymbol::Exports),
             annotations,
         );
         if let Some(i) = i {
@@ -455,7 +443,7 @@ fn get_import_symbol_from_import(specifier: &ImportSpecifier) -> ImportedSymbol
             _ => local.sym.clone(),
         }),
         ImportSpecifier::Default(..) => ImportedSymbol::Symbol(js_word!("default")),
-        ImportSpecifier::Namespace(..) => ImportedSymbol::Namespace,
+        ImportSpecifier::Namespace(..) => ImportedSymbol::Exports,
     }
 }
 
@@ -465,6 +453,6 @@ fn get_import_symbol_from_export(specifier: &ExportSpecifier) -> ImportedSymbol
             ImportedSymbol::Symbol(orig_name(orig))
         }
         ExportSpecifier::Default(..) => ImportedSymbol::Symbol(js_word!("default")),
-        ExportSpecifier::Namespace(..) => ImportedSymbol::Namespace,
+        ExportSpecifier::Namespace(..) => ImportedSymbol::Exports,
     }
 }

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

@@ -3588,8 +3588,7 @@ mod tests {
                 let top_level_mark = Mark::new();
                 m.visit_mut_with(&mut resolver(unresolved_mark, top_level_mark, false));
 
-                let eval_context =
-                    EvalContext::new(&m, unresolved_mark, top_level_mark, false, None);
+                let eval_context = EvalContext::new(&m, unresolved_mark, top_level_mark, None);
 
                 let mut var_graph = create_graph(&m, &eval_context);
 

crates/turbopack-ecmascript/src/lib.rs

@@ -120,6 +120,9 @@ pub enum TreeShakingMode {
     ReexportsOnly,
 }
 
+#[turbo_tasks::value(transparent)]
+pub struct OptionTreeShaking(pub Option<TreeShakingMode>);
+
 #[turbo_tasks::value(shared, serialization = "auto_for_input")]
 #[derive(PartialOrd, Ord, Hash, Debug, Default, Copy, Clone)]
 pub struct EcmascriptOptions {
@@ -139,6 +142,11 @@ pub struct EcmascriptOptions {
     /// If false, they will reference the whole directory. If true, they won't
     /// reference anything and lead to an runtime error instead.
     pub ignore_dynamic_requests: bool,
+
+    /// The list of export names that should make tree shaking bail off. This is
+    /// required because tree shaking can split imports like `export const
+    /// runtime = 'edge'` as a separate module.
+    pub special_exports: Vc<Vec<RcStr>>,
 }
 
 #[turbo_tasks::value(serialization = "auto_for_input")]

crates/turbopack-ecmascript/src/minify.rs

@@ -54,9 +54,12 @@ pub async fn minify(path: Vc<FileSystemPath>, code: Vc<Code>) -> Result<Vc<Code>
         GLOBALS.set(&Default::default(), || {
             let program = match parser.parse_program() {
                 Ok(program) => program,
-                Err(_error) => {
+                Err(err) => {
                     // TODO should emit an issue
-                    bail!("failed to parse source code")
+                    bail!(
+                        "failed to parse source code\n{err:?}\n{}",
+                        code.source_code().to_str()?
+                    )
                 }
             };
             let comments = SingleThreadedComments::default();

crates/turbopack-ecmascript/src/parse.rs

@@ -432,7 +432,6 @@ async fn parse_content(
                 &parsed_program,
                 unresolved_mark,
                 top_level_mark,
-                false,
                 Some(source),
             );
 

crates/turbopack-ecmascript/src/references/esm/base.rs

@@ -96,6 +96,7 @@ pub struct EsmAssetReference {
     pub issue_source: Option<Vc<IssueSource>>,
     pub export_name: Option<Vc<ModulePart>>,
     pub import_externals: bool,
+    pub special_exports: Vc<Vec<RcStr>>,
 }
 
 /// A list of [EsmAssetReference]s
@@ -121,6 +122,7 @@ impl EsmAssetReference {
         issue_source: Option<Vc<IssueSource>>,
         annotations: Value<ImportAnnotations>,
         export_name: Option<Vc<ModulePart>>,
+        special_exports: Vc<Vec<RcStr>>,
         import_externals: bool,
     ) -> Vc<Self> {
         Self::cell(EsmAssetReference {
@@ -130,6 +132,7 @@ impl EsmAssetReference {
             annotations: annotations.into_value(),
             export_name,
             import_externals,
+            special_exports,
         })
     }
 

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

@@ -353,6 +353,7 @@ struct AnalysisState<'a> {
     // the object allocation.
     first_import_meta: bool,
     tree_shaking_mode: Option<TreeShakingMode>,
+    special_exports: Vc<Vec<RcStr>>,
     import_externals: bool,
     ignore_dynamic_requests: bool,
 }
@@ -412,6 +413,7 @@ pub(crate) async fn analyse_ecmascript_module_internal(
     let options = raw_module.options;
     let compile_time_info = raw_module.compile_time_info;
     let options = options.await?;
+    let special_exports = options.special_exports;
     let import_externals = options.import_externals;
 
     let origin = Vc::upcast::<Box<dyn ResolveOrigin>>(module);
@@ -428,7 +430,7 @@ pub(crate) async fn analyse_ecmascript_module_internal(
 
     let parsed = if let Some(part) = part {
         let parsed = parse(source, ty, transforms);
-        let split_data = split(source.ident(), source, parsed);
+        let split_data = split(source.ident(), source, parsed, special_exports);
         part_of_module(split_data, part)
     } else {
         parse(source, ty, transforms)
@@ -576,7 +578,6 @@ pub(crate) async fn analyse_ecmascript_module_internal(
                     ImportedSymbol::Symbol(name) => Some(ModulePart::export((&**name).into())),
                     ImportedSymbol::Part(part_id) => Some(ModulePart::internal(*part_id)),
                     ImportedSymbol::Exports => Some(ModulePart::exports()),
-                    ImportedSymbol::Namespace => None,
                 },
                 Some(TreeShakingMode::ReexportsOnly) => match &r.imported_symbol {
                     ImportedSymbol::ModuleEvaluation => {
@@ -586,10 +587,10 @@ pub(crate) async fn analyse_ecmascript_module_internal(
                     ImportedSymbol::Symbol(name) => Some(ModulePart::export((&**name).into())),
                     ImportedSymbol::Part(part_id) => Some(ModulePart::internal(*part_id)),
                     ImportedSymbol::Exports => None,
-                    ImportedSymbol::Namespace => None,
                 },
                 None => None,
             },
+            special_exports,
             import_externals,
         );
 
@@ -814,6 +815,7 @@ pub(crate) async fn analyse_ecmascript_module_internal(
         first_import_meta: true,
         tree_shaking_mode: options.tree_shaking_mode,
         import_externals: options.import_externals,
+        special_exports: options.special_exports,
         ignore_dynamic_requests: options.ignore_dynamic_requests,
     };
 
@@ -1972,6 +1974,7 @@ async fn handle_free_var_reference(
                         .map(|export| ModulePart::export(export.clone())),
                     None => None,
                 },
+                state.special_exports,
                 state.import_externals,
             )
             .resolve()

crates/turbopack-ecmascript/src/tree_shake/asset.rs

@@ -23,7 +23,7 @@ use crate::{
 /// This type is used for an advanced tree shkaing.
 #[turbo_tasks::value]
 pub struct EcmascriptModulePartAsset {
-    pub(crate) full_module: Vc<EcmascriptModuleAsset>,
+    pub full_module: Vc<EcmascriptModuleAsset>,
     pub(crate) part: Vc<ModulePart>,
     pub(crate) import_externals: bool,
 }