fix(fetch): serialise empty array in 'data' as JSON

Author: mxschmitt

playwright/_impl/_fetch.py

@@ -338,7 +338,7 @@ async def _inner_fetch(
         form_data: Optional[List[NameValue]] = None
         multipart_data: Optional[List[FormField]] = None
         post_data_buffer: Optional[bytes] = None
-        if data:
+        if data is not None:
             if isinstance(data, str):
                 if is_json_content_type(serialized_headers):
                     json_data = data if is_json_parsable(data) else json.dumps(data)

tests/async/test_fetch_global.py

@@ -457,3 +457,14 @@ async def test_should_serialize_null_values_in_json(
     assert response.status == 200
     assert await response.text() == '{"foo": null}'
     await request.dispose()
+
+
+async def test_should_serialize_empty_array_as_json(
+    playwright: Playwright, server: Server
+) -> None:
+    request = await playwright.request.new_context()
+    server.set_route("/echo", lambda req: (req.write(req.post_body), req.finish()))
+    response = await request.post(server.PREFIX + "/echo", data=[])
+    assert response.status == 200
+    assert await response.text() == "[]"
+    await request.dispose()