bundler: name the namespace of an external export * in a non-entry module

src/bundler/linker_context/scanImportsAndExports.rs

@@ -1291,9 +1291,18 @@ pub(crate) fn scan_imports_and_exports(
                             Index::source(source_index),
                         )?;
                         col!(ast_flags_list)[id].insert(AstFlags::USES_EXPORTS_REF);
-                        col!(import_records_list)[id].as_mut_slice()[*import_record_index as usize]
-                            .flags
-                            .insert(ImportRecordFlags::CALLS_RUNTIME_RE_EXPORT_FN);
+                        let flags = &mut col!(import_records_list)[id].as_mut_slice()
+                            [*import_record_index as usize]
+                            .flags;
+                        flags.insert(ImportRecordFlags::CALLS_RUNTIME_RE_EXPORT_FN);
+                        // `convert_stmts_for_chunk` prints an external one as
+                        // `import * as ns`, and the printer names `ns` only for
+                        // a record that contains an import star.
+                        if !rec_source_index.is_valid()
+                            && output_format.keep_es6_import_export_syntax()
+                        {
+                            flags.insert(ImportRecordFlags::CONTAINS_IMPORT_STAR);
+                        }
                         re_export_uses += 1;
                     }
                 }

test/bundler/esbuild/importstar.test.ts

@@ -1437,6 +1437,48 @@ describe.concurrent("bundler", () => {
       stdout: '{"inner":{"b":456},"a":123,"b":456}',
     },
   });
+  // ESM output imports an inner file's external `export *` as a namespace, for
+  // `__reExport` to copy from.
+  itBundled("importstar/ReExportStarEntryPointAndInnerFileExternalESM", {
+    files: {
+      "/entry.js": /* js */ `
+        export * from 'a'
+        import * as inner from './inner.js'
+        export { inner }
+      `,
+      "/inner.js": `export * from 'b'`,
+    },
+    format: "esm",
+    external: ["a", "b"],
+    runtimeFiles: {
+      "/test.js": /* js */ `
+      import * as out from './out.js'
+      console.log(JSON.stringify(out))
+      `,
+      "/node_modules/a/index.js": `export const a = 123;`,
+      "/node_modules/b/index.js": `export const b = 456;`,
+    },
+    run: {
+      file: "/test.js",
+      stdout: '{"a":123,"inner":{"b":456}}',
+    },
+  });
+  itBundled("importstar/ReExportStarBuiltinFromLazyModule", {
+    files: {
+      "/entry.js": /* js */ `
+        import * as ns from './re.js'
+        const lazy = await import('./lazy.js')
+        console.log(typeof ns.join, ns.own, typeof lazy.readFileSync)
+      `,
+      "/re.js": `export * from 'node:path'; export const own = 1`,
+      "/lazy.js": `export * from 'node:fs'`,
+    },
+    target: "bun",
+    format: "esm",
+    run: {
+      stdout: "function 1 function",
+    },
+  });
   itBundled("importstar/ReExportStarEntryPointAndInnerFile", {
     files: {
       "/entry.js": /* js */ `