fix(avito): post-merge polish — unify fetch_mode guard + empty-render guard (#1811) (#1909)

avito SERP browser post-merge polish (#1811): unify fetch_mode guard, empty-render guard, debug logging. Refs #1811

tradein-mvp/backend/app/services/scrape_pipeline.py

@@ -757,6 +757,11 @@ async def run_avito_city_sweep(
                     scraper = AvitoScraper()
                     if browser_mode:
                         scraper._browser = shared_bf
+                        # Shared-browser режим: _cffi=None → curl_cffi-fallback на
+                        # firewall пропускается (by design). Логируем для observability.
+                        logger.debug(
+                            "avito pipeline-mode: shared browser only, no cffi fallback"
+                        )
                     else:
                         scraper._cffi = session
 
@@ -1324,6 +1329,9 @@ async def run_avito_newbuilding_sweep(
             scraper = AvitoScraper()
             if browser_mode:
                 scraper._browser = shared_bf
+                # Shared-browser режим: _cffi=None → curl_cffi-fallback на firewall
+                # пропускается (by design). Логируем для observability.
+                logger.debug("avito pipeline-mode: shared browser only, no cffi fallback")
             else:
                 scraper._cffi = session
 

tradein-mvp/backend/app/services/scrapers/avito.py

@@ -352,7 +352,7 @@ class AvitoScraper(BaseScraper):
                 logger.warning(
                     "avito: proactive IP rotate at sweep start raised — proceeding", exc_info=True
                 )
-        if settings.scraper_fetch_mode != "curl_cffi":
+        if settings.scraper_fetch_mode == "browser":
             # Default (#1805): SERP-фетч через camoufox (tradein-browser per-provider
             # + ротирующий backconnect-прокси). curl_cffi поднимаем тут же как
             # FALLBACK — если браузер отдаёт firewall/пусто, _fetch_serp_html делает
@@ -546,6 +546,12 @@ class AvitoScraper(BaseScraper):
                 raise AvitoRateLimitedError(
                     f"avito SERP browser-sidecar error (page={page}): {error_text[:200]}"
                 ) from exc
+            # Пустой рендер ("" / None) = таймаут рендера sidecar'а, НЕ firewall:
+            # _is_firewall_page("") вернул бы False → пустой HTML утёк бы как
+            # «валидный». Возвращаем None — caller (fetch_around) трактует это как
+            # конец пагинации (break), а не как бан.
+            if not html:
+                return None
             if not _is_firewall_page(html):
                 return html
             if rot_done < max_rot and await self._rotate_ip():

tradein-mvp/backend/tests/test_avito_browser_mode.py

@@ -175,7 +175,8 @@ async def test_fetch_serp_html_browser_mode_returns_html() -> None:
 
     assert result == _NORMAL_HTML
     mock_browser.fetch.assert_awaited_once_with("https://www.avito.ru/test")
-    # _cffi was never set — assert remains None
+    # _cffi not armed (direct _browser assignment bypasses __aenter__, which would
+    # otherwise build the curl_cffi fallback session); the browser path never touches it.
     assert scraper._cffi is None