fix(pack): isolate runtime public path for async chunks

crates/pack-core/src/shared/transforms/webpack_public_path.rs

@@ -13,8 +13,8 @@ use turbopack_ecmascript::{CustomTransformer, TransformContext};
 
 use super::{EcmascriptTransformStage, get_ecma_transform_rule};
 
-/// Returns a rule that maps webpack's runtime public path global onto utoopack's
-/// existing runtime public path hook.
+/// Returns a rule that maps webpack's runtime public path global onto the
+/// current utoopack runtime's public path.
 pub fn get_webpack_public_path_transform_rule() -> ModuleRule {
     get_ecma_transform_rule(
         Box::new(WebpackPublicPathTransformer {}),
@@ -97,20 +97,20 @@ impl WebpackPublicPathVisitor {
         sym == &atom!("__webpack_public_path__") && ctxt == self.unresolved_ctxt
     }
 
-    fn global_public_path_member(&self, span: swc_core::common::Span) -> MemberExpr {
+    fn runtime_public_path_member(&self, span: swc_core::common::Span) -> MemberExpr {
         MemberExpr {
             span,
             obj: Box::new(Expr::Ident(Ident::new(
-                atom!("globalThis"),
+                atom!("__turbopack_context__"),
                 span,
-                self.unresolved_ctxt,
+                SyntaxContext::empty(),
             ))),
-            prop: MemberProp::Ident(IdentName::new(atom!("publicPath"), span)),
+            prop: MemberProp::Ident(IdentName::new(atom!("runtimePublicPath"), span)),
         }
     }
 
-    fn global_public_path_expr(&self, span: swc_core::common::Span) -> Expr {
-        Expr::Member(self.global_public_path_member(span))
+    fn runtime_public_path_expr(&self, span: swc_core::common::Span) -> Expr {
+        Expr::Member(self.runtime_public_path_member(span))
     }
 }
 
@@ -121,7 +121,7 @@ impl VisitMut for WebpackPublicPathVisitor {
                 if self.is_webpack_public_path(&binding_ident.id.sym, binding_ident.id.ctxt) =>
             {
                 assign_expr.left = AssignTarget::Simple(SimpleAssignTarget::Member(
-                    self.global_public_path_member(binding_ident.id.span),
+                    self.runtime_public_path_member(binding_ident.id.span),
                 ));
             }
             _ => {
@@ -136,7 +136,7 @@ impl VisitMut for WebpackPublicPathVisitor {
         if let Expr::Ident(ident) = expr
             && self.is_webpack_public_path(&ident.sym, ident.ctxt)
         {
-            *expr = self.global_public_path_expr(ident.span);
+            *expr = self.runtime_public_path_expr(ident.span);
             return;
         }
 

crates/pack-tests/tests/snapshot/basic/multi_server_entries/output/server/entries/server.5d80c3de.js

@@ -531,6 +531,15 @@ contextPrototype.U = relativeURL;
 contextPrototype.z = requireStub;
 // Make `globalThis` available to the module in a way that cannot be shadowed by a local variable.
 contextPrototype.g = globalThis;
+// Each runtime keeps its own public path. Other applications on the page may
+// change the global path after this runtime has started.
+let runtimePublicPath = typeof globalThis !== 'undefined' ? globalThis.publicPath : undefined;
+Object.defineProperty(contextPrototype, 'runtimePublicPath', {
+    get: ()=>runtimePublicPath,
+    set: (value)=>{
+        runtimePublicPath = value;
+    }
+});
 let cachedAutomaticPublicPath;
 function getAutomaticPublicPath() {
     if (cachedAutomaticPublicPath !== undefined) {
@@ -554,13 +563,13 @@ function getAutomaticPublicPath() {
 }
 /**
  * Gets the public path for runtime assets.
- * Checks globalThis.publicPath and falls back to "/".
+ * Uses this runtime's public path and falls back to "/".
  */ function getPublicPath(mode) {
     if (mode === 'auto') {
         return getAutomaticPublicPath();
     }
-    if (typeof globalThis !== 'undefined' && typeof globalThis.publicPath === 'string') {
-        const publicPath = globalThis.publicPath;
+    if (typeof runtimePublicPath === 'string') {
+        const publicPath = runtimePublicPath;
         return publicPath.endsWith('/') ? publicPath : `${publicPath}/`;
     }
     return '/';

crates/pack-tests/tests/snapshot/basic/multi_server_entries/output/server/stats.json

@@ -85,7 +85,7 @@
       "entry": false,
       "recorded": false,
       "id": "entries/detail-server.5d841f26.js",
-      "size": 32579,
+      "size": 32928,
       "hash": "",
       "files": [
         "entries/detail-server.5d841f26.js"
@@ -97,7 +97,7 @@
       "entry": false,
       "recorded": false,
       "id": "entries/index-server.5c83aa4e.js",
-      "size": 32591,
+      "size": 32940,
       "hash": "",
       "files": [
         "entries/index-server.5c83aa4e.js"
@@ -109,7 +109,7 @@
       "entry": false,
       "recorded": false,
       "id": "entries/server.5d80c3de.js",
-      "size": 32558,
+      "size": 32907,
       "hash": "",
       "files": [
         "entries/server.5d80c3de.js"
@@ -145,7 +145,7 @@
       "type": "asset",
       "name": "entries/detail-server.5d841f26.js",
       "info": {},
-      "size": 32579,
+      "size": 32928,
       "emitted": false,
       "comparedForEmit": false,
       "cached": false,
@@ -157,7 +157,7 @@
       "type": "asset",
       "name": "entries/index-server.5c83aa4e.js",
       "info": {},
-      "size": 32591,
+      "size": 32940,
       "emitted": false,
       "comparedForEmit": false,
       "cached": false,
@@ -169,7 +169,7 @@
       "type": "asset",
       "name": "entries/server.5d80c3de.js",
       "info": {},
-      "size": 32558,
+      "size": 32907,
       "emitted": false,
       "comparedForEmit": false,
       "cached": false,

crates/pack-tests/tests/snapshot/hmr/lazy_dynamic_imports/output/main.js

@@ -546,6 +546,15 @@ contextPrototype.U = relativeURL;
 contextPrototype.z = requireStub;
 // Make `globalThis` available to the module in a way that cannot be shadowed by a local variable.
 contextPrototype.g = globalThis;
+// Each runtime keeps its own public path. Other applications on the page may
+// change the global path after this runtime has started.
+let runtimePublicPath = typeof globalThis !== 'undefined' ? globalThis.publicPath : undefined;
+Object.defineProperty(contextPrototype, 'runtimePublicPath', {
+    get: ()=>runtimePublicPath,
+    set: (value)=>{
+        runtimePublicPath = value;
+    }
+});
 let cachedAutomaticPublicPath;
 function getAutomaticPublicPath() {
     if (cachedAutomaticPublicPath !== undefined) {
@@ -569,13 +578,13 @@ function getAutomaticPublicPath() {
 }
 /**
  * Gets the public path for runtime assets.
- * Checks globalThis.publicPath and falls back to "/".
+ * Uses this runtime's public path and falls back to "/".
  */ function getPublicPath(mode) {
     if (mode === 'auto') {
         return getAutomaticPublicPath();
     }
-    if (typeof globalThis !== 'undefined' && typeof globalThis.publicPath === 'string') {
-        const publicPath = globalThis.publicPath;
+    if (typeof runtimePublicPath === 'string') {
+        const publicPath = runtimePublicPath;
         return publicPath.endsWith('/') ? publicPath : `${publicPath}/`;
     }
     return '/';