fix: refuse a platform scrape that lists no file

scraper_cli wrote a platform YAML with no system when the parse came back
empty, and exited 0. It now exits 1 before writing, unless the scraper
declares lists_files = False (RetroPie, whose files are inherited); RetroPie
in turn raises when its archive declares no package.

scripts/scraper/base_scraper.py

@@ -164,6 +164,11 @@ def fetch_bytes(
 class BaseScraper(ABC):
     """Abstract base class for platform BIOS requirement scrapers."""
 
+    # False for a platform whose file list is inherited and whose scraper
+    # reads only its core list (RetroPie). Otherwise an empty read is an
+    # upstream that changed shape, never a platform with no file.
+    lists_files: bool = True
+
     def __init__(self, url: str = "") -> None:
         self.url = url
         self._raw_data: str | None = None
@@ -366,6 +371,12 @@ def scraper_cli(
         reqs = scraper.fetch_requirements()
     except (OSError, ValueError, RuntimeError) as e:
         _exit_on_scrape_error(e)
+    if scraper.lists_files and not reqs:
+        # Written, an empty read became a platform with no system that
+        # verify and the pack count 0/0 and call consistent.
+        _exit_on_scrape_error(RuntimeError(
+            f"{scraper_class.__module__}: upstream returned no BIOS entry"
+        ))
 
     if args.dry_run:
         by_system: dict[str, list] = {}
@@ -425,6 +436,12 @@ def scraper_cli(
                 if req.zipped_file:
                     entry["zipped_file"] = req.zipped_file
                 config["systems"][sys_id]["files"].append(entry)
+        if scraper.lists_files and not any(
+            (system or {}).get("files") for system in (config.get("systems") or {}).values()
+        ):
+            _exit_on_scrape_error(RuntimeError(
+                f"{scraper_class.__module__}: the generated platform lists no file"
+            ))
         # Merge into existing YAML: preserve fields the scraper doesn't generate
         # (data_directories, case_insensitive_fs, manually added metadata).
         # The scraper replaces systems + files, everything else is preserved.

scripts/scraper/retropie_scraper.py

@@ -59,6 +59,8 @@ _PACKAGE_DIRS = _SCRIPT_SECTIONS
 class Scraper(BaseScraper):
     """Scraper for the RetroPie package list."""
 
+    lists_files = False
+
     def __init__(self, url: str | None = None) -> None:
         # The package list is read from master: the commit read is recorded.
         if url is None:
@@ -122,6 +124,8 @@ class Scraper(BaseScraper):
                 else:
                     found.add(match.group(1))
 
+        if not found:
+            raise ValueError(f"{self.url}: no rp_module_id under {SCRIPTMODULES}/")
         self._modules = sorted(found)
         return self._modules