LibJS: Allow exporting any imported bindings

Author: https://github.com/davidot
Commit: https://github.com/SerenityOS/serenity/commit/faf1430ce4
Pull-request: https://github.com/SerenityOS/serenity/pull/15100
Reviewed-by: https://github.com/linusg

Userland/Libraries/LibJS/Parser.cpp

@@ -565,8 +565,15 @@ void Parser::parse_module(Program& program)
                 if (name == exported_name)
                     found = true;
             });
+            for (auto& import : program.imports()) {
+                if (import.has_bound_name(exported_name)) {
+                    found = true;
+                    break;
+                }
+            }
+
             if (!found)
-                syntax_error(String::formatted("'{}' is not declared", exported_name));
+                syntax_error(String::formatted("'{}' in export is not declared", exported_name), export_statement.source_range().start);
         }
     }
 }

Userland/Libraries/LibJS/Tests/modules/basic-modules.js

@@ -190,6 +190,10 @@ describe("in- and exports", () => {
     test("can have multiple star imports even from the same file", () => {
         expectModulePassed("./multiple-star-imports.mjs");
     });
+
+    test("can export namespace via binding", () => {
+        expectModulePassed("./re-export-namespace-via-binding.mjs");
+    });
 });
 
 describe("loops", () => {

Userland/Libraries/LibJS/Tests/modules/re-export-namespace-via-binding.mjs

@@ -0,0 +1,7 @@
+import * as namespace from "./default-and-star-export.mjs";
+import { "*" as fromStar } from "./default-and-star-export.mjs";
+export { namespace };
+
+import { namespace as nm } from "./re-export-namespace-via-binding.mjs";
+
+export const passed = nm === namespace && fromStar === namespace["*"];