Keep the export default wrapper around a default-exported template

src/parse.js

@@ -237,9 +237,25 @@ export function toTree(source, options = {}) {
   function walkWithKeys(node, parentPath) {
     if (!node || !node.type) return;
 
+    const path = { node, parent: parentPath?.node ?? null, parentPath };
+
     if (hasTemplates && PLACEHOLDER_TYPES.has(node.type)) {
       const parseResult = matchPlaceholder(node);
-      if (parseResult) {
+      if (parseResult && node.type === "ExportDefaultDeclaration") {
+        // `export default <template>...</template>`: keep the export wrapper
+        // and splice its declaration, so the tree (and `print`) still carry
+        // the `export default`.
+        const ast = processPlaceholder(parseResult, node.declaration);
+        node.declaration = ast;
+        setParent(ast, node);
+        if (hasVisitors && !seen.has(node)) {
+          seen.add(node);
+          const handler = visitors[node.type];
+          if (handler) handler(node, path);
+          walkWithKeys(ast, path);
+        }
+        return;
+      } else if (parseResult) {
         // Splice in place: write the GlimmerTemplate directly into the parent's
         // slot instead of allocating new ancestor objects. This preserves node
         // identity for every ancestor, which matters for WeakMap-keyed data
@@ -250,14 +266,12 @@ export function toTree(source, options = {}) {
         setParent(ast, parent);
         // Recurse into the Glimmer subtree so visitors fire on its nodes too.
         // The Glimmer root's parentPath reflects its true JS parent — the
-        // placeholder (UnaryExpression / StaticBlock) is an internal artifact.
+        // placeholder (`void` expression / StaticBlock) is an internal artifact.
         if (hasVisitors) walkWithKeys(ast, parentPath);
         return;
       }
     }
 
-    const path = { node, parent: parentPath?.node ?? null, parentPath };
-
     if (hasVisitors && !seen.has(node)) {
       seen.add(node);
       const handler = visitors[node.type];

tests/parse.test.js

@@ -184,6 +184,14 @@ describe("parse", () => {
     ]);
   });
 
+  it("keeps the export default wrapper around a default-exported template", () => {
+    const source = `export default <template>hi</template>;\n`;
+    const ast = parse(source);
+
+    expect(ast.program.body.map((node) => node.type)).toEqual(["ExportDefaultDeclaration"]);
+    expect(ast.program.body[0].declaration.type).toBe("GlimmerTemplate");
+  });
+
   it("handles multiple classes with templates", () => {
     const source = `class A extends Component {
   <template><div>A</div></template>

tests/print-file.test.js

@@ -11,6 +11,11 @@ describe("print(File)", () => {
     `);
   });
 
+  it("round-trips a default-exported template", () => {
+    const source = `export default <template>hi</template>;`;
+    expect(print(toTree(source))).toBe("export default <template>hi</template>");
+  });
+
   it("prints an empty File", () => {
     const tree = toTree(``, { filePath: "m.js" });