fix: refuse a file read off the pinned revision

pinned_base returned an empty base when the platform's source named no
revision or no longer ended in the exported file, and the exporter's
own branch URL was then patched without a word. Every file an export
reads must now carry the revision the platform YAML records, or the
platform fails and asks for a rescrape. The check covers every file of
every platform: ROCKNIX's second file, RetroDECK's manifests and
RetroPie's tarball were checked by nothing before.

scripts/export_native.py

@@ -236,6 +236,41 @@ def wanted_sources(
     }
 
 
+_REVISION = (
+    re.compile(r"^https://raw\.githubusercontent\.com/[^/]+/[^/]+/([^/]+)/"),
+    re.compile(r"^https://github\.com/[^/]+/[^/]+/(?:tree|blob)/([^/]+)"),
+    re.compile(r"^https://gitlab\.com/.+?/-/(?:raw|archive)/([^/]+)/"),
+    re.compile(r"^https://codeload\.github\.com/[^/]+/[^/]+/tar\.gz/([^/]+)$"),
+)
+
+
+def source_revision(source: str) -> str:
+    """The revision a platform YAML's source: URL names, '' when none."""
+    for pattern in _REVISION:
+        match = pattern.match(source)
+        if match:
+            return match.group(1)
+    return ""
+
+
+def unpinned(wanted: dict[str, str], scraped: dict | None) -> list[str]:
+    """Every file the export would read off the revision the YAML records.
+
+    pinned_base() returned '' when the source named no revision or no
+    longer ended in the file, and the exporter's own branch URL was then
+    patched without a word: a file our transcription never described.
+    """
+    source = str((scraped or {}).get("source", ""))
+    revision = source_revision(source)
+    if not revision:
+        return [f"the platform's source names no revision ({source or 'none'}): rescrape it"]
+    return [
+        f"{relative} would be read at {url}, not at {revision}: rescrape the platform"
+        for relative, url in wanted.items()
+        if f"/{revision}/" not in url and not url.endswith(f"/{revision}")
+    ]
+
+
 _CODELOAD = re.compile(r"^https://codeload\.github\.com/([^/]+)/([^/]+)/tar\.gz/")
 
 
@@ -381,6 +416,9 @@ def refresh_cache(
     systems, _ = build_native_model(truth or {}, scraped)
     exporter = exporter_class()
     wanted = wanted_sources(exporter, systems, scraped)
+    off_pin = unpinned(wanted, scraped)
+    if off_pin:
+        return False, off_pin
     _, missing = collect_originals(
         exporter, systems, upstream_dir, True, scraped, refresh=True
     )
@@ -496,6 +534,9 @@ def export_platform(
         return False, ["nothing to write: neither the platform nor the truth has data"]
 
     exporter = exporter_class()
+    off_pin = unpinned(wanted_sources(exporter, systems, scraped), scraped)
+    if off_pin:
+        return False, off_pin
     originals, missing = collect_originals(
         exporter, systems, upstream_dir, allow_fetch, scraped
     )

tests/test_exporters.py

@@ -34,6 +34,7 @@ sys.path.insert(0, str(REPO_ROOT / "scripts"))
 from common import (  # noqa: E402
     list_registered_platforms,
     load_platform_config,
+    native_layer,
     parse_untrusted_xml,
 )
 from exporter import discover_exporters  # noqa: E402
@@ -697,6 +698,35 @@ class PinnedRevision(unittest.TestCase):
                 base = pinned_base(dict(exporters[name].native_sources()), config)
                 self.assertTrue(base.startswith("https://"), base)
 
+    def test_every_file_of_every_platform_is_read_at_the_pinned_revision(self):
+        """Checked on five platforms by their base only: ROCKNIX's second
+        file, RetroDECK's manifests and RetroPie's tarball were never
+        looked at, and a URL that fell back to a branch passed."""
+        import export_native  # noqa: PLC0415
+
+        for name, exporter_class in discover_exporters().items():
+            with self.subTest(platform=name):
+                config = native_layer(load_platform_config(name, str(REPO_ROOT / "platforms")))
+                systems, _ = build_native_model({}, config)
+                wanted = export_native.wanted_sources(exporter_class(), systems, config)
+                self.assertTrue(wanted)
+                self.assertEqual(export_native.unpinned(wanted, config), [])
+
+    def test_a_file_read_off_the_pinned_revision_is_named(self):
+        import export_native  # noqa: PLC0415
+
+        pinned = {"source": "https://raw.githubusercontent.com/o/r/v1.0/list.txt"}
+        self.assertEqual(export_native.unpinned(
+            {"list.txt": "https://raw.githubusercontent.com/o/r/v1.0/list.txt"}, pinned), [])
+        moved = export_native.unpinned(
+            {"list.txt": "https://raw.githubusercontent.com/o/r/master/list.txt"}, pinned)
+        self.assertEqual(len(moved), 1)
+        self.assertIn("v1.0", moved[0])
+        bare = export_native.unpinned(
+            {"x.json": "https://raw.githubusercontent.com/o/r/main/x.json"},
+            {"source": "https://github.com/RetroDECK/components"})
+        self.assertIn("names no revision", bare[0])
+
 
 class _OneFileExporter:
     """An exporter reduced to what collect_originals reads."""