fix(turbopack): Improve analyzer of tree-shaking pass (#70017)

### What?

Improve the graph analyzer of the tree-shaking pass. This PR does **not** server-action specific changes for tree shaking.

### Why?

This is part of [the tree-shaking PR](#69344).

### How?

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

@@ -49,15 +49,15 @@ pub async fn minify(path: Vc<FileSystemPath>, code: Vc<Code>) -> Result<Vc<Code>
         None,
     );
     let mut parser = Parser::new_from(lexer);
-    // TODO should use our own handler that emits issues instead.
+
     let program = try_with_handler(cm.clone(), Default::default(), |handler| {
         GLOBALS.set(&Default::default(), || {
             let program = match parser.parse_program() {
                 Ok(program) => program,
                 Err(err) => {
-                    // TODO should emit an issue
+                    err.into_diagnostic(handler).emit();
                     bail!(
-                        "failed to parse source code\n{err:?}\n{}",
+                        "failed to parse source code\n{}",
                         code.source_code().to_str()?
                     )
                 }

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

@@ -1,4 +1,5 @@
 use std::{
+    borrow::Cow,
     collections::{BTreeMap, HashSet},
     ops::ControlFlow,
 };
@@ -9,8 +10,9 @@ use serde::{Deserialize, Serialize};
 use swc_core::{
     common::DUMMY_SP,
     ecma::ast::{
-        self, ComputedPropName, Expr, ExprStmt, Ident, KeyValueProp, Lit, MemberExpr, MemberProp,
-        ModuleItem, ObjectLit, Program, Prop, PropName, PropOrSpread, Script, Stmt, Str,
+        self, AssignTarget, ComputedPropName, Expr, ExprStmt, Ident, KeyValueProp, Lit, MemberExpr,
+        MemberProp, ModuleItem, ObjectLit, Program, Prop, PropName, PropOrSpread, Script,
+        SimpleAssignTarget, Stmt, Str,
     },
     quote, quote_expr,
 };
@@ -28,7 +30,7 @@ use super::base::ReferencedAsset;
 use crate::{
     chunk::{EcmascriptChunkPlaceable, EcmascriptExports},
     code_gen::{CodeGenerateable, CodeGeneration},
-    create_visitor,
+    create_visitor, magic_identifier,
     references::esm::base::insert_hoisted_stmt,
 };
 
@@ -497,12 +499,17 @@ impl CodeGenerateable for EsmExports {
                     "(() => { throw new Error(\"Failed binding. See build errors!\"); })" as Expr,
                 )),
                 EsmExport::LocalBinding(name, mutable) => {
+                    let local = if name == "default" {
+                        Cow::Owned(magic_identifier::mangle("default export"))
+                    } else {
+                        Cow::Borrowed(name.as_str())
+                    };
                     if *mutable {
                         Some(quote!(
                             "([() => $local, ($new) => $local = $new])" as Expr,
-                            local = Ident::new((name as &str).into(), DUMMY_SP, Default::default()),
+                            local = Ident::new(local.into(), DUMMY_SP, Default::default()),
                             new = Ident::new(
-                                format!("{name}_new_value").into(),
+                                format!("new_{name}").into(),
                                 DUMMY_SP,
                                 Default::default()
                             ),
@@ -518,9 +525,13 @@ impl CodeGenerateable for EsmExports {
                     let referenced_asset =
                         ReferencedAsset::from_resolve_result(esm_ref.resolve_reference()).await?;
                     referenced_asset.get_ident().await?.map(|ident| {
-                        let expr = Expr::Member(MemberExpr {
+                        let expr = MemberExpr {
                             span: DUMMY_SP,
-                            obj: Box::new(Expr::Ident(Ident::new(ident.into(), DUMMY_SP, Default::default()))),
+                            obj: Box::new(Expr::Ident(Ident::new(
+                                ident.into(),
+                                DUMMY_SP,
+                                Default::default(),
+                            ))),
                             prop: MemberProp::Computed(ComputedPropName {
                                 span: DUMMY_SP,
                                 expr: Box::new(Expr::Lit(Lit::Str(Str {
@@ -529,17 +540,22 @@ impl CodeGenerateable for EsmExports {
                                     raw: None,
                                 }))),
                             }),
-                        });
+                        };
                         if *mutable {
                             quote!(
-                                "([() => $expr, ($new) => $expr = $new])" as Expr,
-                                expr: Expr = expr,
-                                new = Ident::new(format!("{name}_new_value").into(), DUMMY_SP, Default::default()),
+                                "([() => $expr, ($new) => $lhs = $new])" as Expr,
+                                expr: Expr = Expr::Member(expr.clone()),
+                                lhs: AssignTarget = AssignTarget::Simple(SimpleAssignTarget::Member(expr)),
+                                new = Ident::new(
+                                    format!("new_{name}").into(),
+                                    DUMMY_SP,
+                                    Default::default()
+                                ),
                             )
                         } else {
                             quote!(
                                 "(() => $expr)" as Expr,
-                                expr: Expr = expr,
+                                expr: Expr = Expr::Member(expr),
                             )
                         }
                     })

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

@@ -11,7 +11,7 @@ use turbopack_core::{
 
 use super::{
     chunk_item::EcmascriptModulePartChunkItem, get_part_id, part_of_module, split, split_module,
-    Key, SplitResult,
+    Key, PartId, SplitResult,
 };
 use crate::{
     chunk::{EcmascriptChunkPlaceable, EcmascriptExports},
@@ -27,7 +27,7 @@ use crate::{
 #[turbo_tasks::value]
 pub struct EcmascriptModulePartAsset {
     pub full_module: Vc<EcmascriptModuleAsset>,
-    pub(crate) part: Vc<ModulePart>,
+    pub part: Vc<ModulePart>,
 }
 
 #[turbo_tasks::value_impl]
@@ -40,15 +40,14 @@ impl EcmascriptParsable for EcmascriptModulePartAsset {
         let split_data = split(this.full_module.ident(), this.full_module.source(), parsed);
         Ok(part_of_module(split_data, this.part))
     }
-
     #[turbo_tasks::function]
-    async fn parse_original(self: Vc<Self>) -> Result<Vc<ParseResult>> {
-        Ok(self.await?.full_module.parse_original())
+    fn parse_original(&self) -> Result<Vc<ParseResult>> {
+        Ok(self.full_module.parse_original())
     }
 
     #[turbo_tasks::function]
-    async fn ty(self: Vc<Self>) -> Result<Vc<EcmascriptModuleAssetType>> {
-        Ok(self.await?.full_module.ty())
+    async fn ty(&self) -> Result<Vc<EcmascriptModuleAssetType>> {
+        Ok(self.full_module.ty())
     }
 }
 
@@ -212,11 +211,17 @@ impl Module for EcmascriptModulePartAsset {
 
         let mut assets = deps
             .iter()
-            .map(|&part_id| {
+            .map(|part_id| {
                 Ok(Vc::upcast(SingleModuleReference::new(
                     Vc::upcast(EcmascriptModulePartAsset::new(
                         self.full_module,
-                        ModulePart::internal(part_id),
+                        match part_id {
+                            PartId::Internal(part_id) => ModulePart::internal(*part_id),
+                            PartId::Export(name) => ModulePart::export(name.clone()),
+                            _ => unreachable!(
+                                "PartId other than Internal and Export should not be used here"
+                            ),
+                        },
                     )),
                     Vc::cell("ecmascript module part".into()),
                 )))