fix: prevent Emulator archive dates from masking version rollback

scripts/update_android_downloads.py

@@ -355,6 +355,11 @@ def parse_releases(source: str, kind: str, accept_all_devsite_expandables: bool
         if previous.fingerprint() != release.fingerprint():
             raise UpdateError(f"{kind} 出现相同版本但下载元数据不同: {release.name} / {release.date_iso}")
         duplicate_count += 1
+    if "Android Emulator" in kind:
+        # Archive insertion dates are not monotonic with Emulator revisions
+        # (37.3.1 was listed after 37.3.3). Keep every validated entry, but
+        # use numeric revision for pages, summaries and channel selection.
+        unique.sort(key=_emulator_order_key, reverse=True)
     return unique, duplicate_count
 
 
@@ -367,6 +372,11 @@ def _release_order_key(release: Release) -> tuple[str, tuple[int, ...], str]:
     return (release.date_iso, _release_version(release), release.name)
 
 
+def _emulator_order_key(release: Release) -> tuple[tuple[int, ...], str, str]:
+    version = _version_from_emulator_name(release.name)
+    return (_version_key(version), release.date_iso, release.name)
+
+
 def _release_id(product: str, release: Release) -> str:
     version = VERSION_RE.search(release.name)
     version_slug = re.sub(r"[^a-z0-9]+", "-", version.group(0).lower()) if version else "unknown"
@@ -520,6 +530,15 @@ def _validate_transition(old: Sequence[Release], new: Sequence[Release], kind: s
     minimum = max(1, int(len(old) * MIN_COUNT_RATIO))
     if len(new) < minimum:
         raise UpdateError(f"{kind} 条目数异常下降: 旧 {len(old)}，新 {len(new)}，最低允许 {minimum}")
+    if kind == "Android Emulator":
+        # Compare maxima within each channel, including unsorted legacy pages.
+        # A newer stable/canary must not hide a regression or missing channel.
+        for channel in {release.channel for release in old}:
+            previous = max((r for r in old if r.channel == channel), key=_emulator_order_key)
+            candidates = [r for r in new if r.channel == channel]
+            if not candidates or max(_emulator_order_key(r)[0] for r in candidates) < _emulator_order_key(previous)[0]:
+                raise UpdateError(f"{kind} {channel} 最新版本倒退或缺失: 旧 {previous.name}")
+        return
     if _release_order_key(new[0]) < _release_order_key(old[0]):
         raise UpdateError(f"{kind} 最新版本倒退: 旧 {old[0].name}，新 {new[0].name}")
 

tests/fixtures/emulator-nonmonotonic-frame.html

@@ -0,0 +1,40 @@
+<!-- Official archive metadata captured 2026-10-08; source order preserved. -->
+            <devsite-expandable class="expandable" is-upgraded="" id="emulator-37-3-1-canary">
+              <p class="expand-control" aria-controls="emulator-37-3-1-canary" aria-expanded="false" tabindex="0" role="button">
+                Android Emulator (37.3.1) Canary
+                <span>Oct 07, 2026</span>
+              </p>
+              <div class="downloads">
+                Zip files
+                Linux: <a href="https://redirector.gvt1.com/edgedl/android/repository/emulator-linux_x64-16373887.zip">emulator-linux_x64-16373887.zip</a> (353795619 bytes)
+                Mac (Intel): <a href="https://redirector.gvt1.com/edgedl/android/repository/emulator-darwin_x64-16373887.zip">emulator-darwin_x64-16373887.zip</a> (492796833 bytes)
+                Mac (Apple Silicon): <a href="https://redirector.gvt1.com/edgedl/android/repository/emulator-darwin_aarch64-16373887.zip">emulator-darwin_aarch64-16373887.zip</a> (419849447 bytes)
+                Windows (64-bit): <a href="https://redirector.gvt1.com/edgedl/android/repository/emulator-windows_x64-16373887.zip">emulator-windows_x64-16373887.zip</a> (459169650 bytes)
+
+                SHA-256 checksums
+                e8f46e19b8dedad03f2387caa2676a6d9b0ddbb3db850202167346da75098260 emulator-linux_x64-16373887.zip
+                903400cabc3d684c8a7d463524990e508412de849a78a00772c22e865d0241e6 emulator-darwin_x64-16373887.zip
+                9d0f6ae4f27a886d947098bb6f5f3148a3f2217ce4a58cb81dbec0222da68d21 emulator-darwin_aarch64-16373887.zip
+                b294385071f0dad738308b91c60f605c4a817c617352136a0b5625e1f800e359 emulator-windows_x64-16373887.zip
+              </div>
+            </devsite-expandable>
+
+            <devsite-expandable class="expandable" is-upgraded="" id="emulator-37-3-3-canary">
+              <p class="expand-control" aria-controls="emulator-37-3-3-canary" aria-expanded="false" tabindex="0" role="button">
+                Android Emulator (37.3.3) Canary
+                <span>Oct 06, 2026</span>
+              </p>
+              <div class="downloads">
+                Zip files
+                Linux: <a href="https://redirector.gvt1.com/edgedl/android/repository/emulator-linux_x64-16489710.zip">emulator-linux_x64-16489710.zip</a> (353959232 bytes)
+                Mac (Intel): <a href="https://redirector.gvt1.com/edgedl/android/repository/emulator-darwin_x64-16489710.zip">emulator-darwin_x64-16489710.zip</a> (493027673 bytes)
+                Mac (Apple Silicon): <a href="https://redirector.gvt1.com/edgedl/android/repository/emulator-darwin_aarch64-16489710.zip">emulator-darwin_aarch64-16489710.zip</a> (420070680 bytes)
+                Windows (64-bit): <a href="https://redirector.gvt1.com/edgedl/android/repository/emulator-windows_x64-16489710.zip">emulator-windows_x64-16489710.zip</a> (459469167 bytes)
+
+                SHA-256 checksums
+                a0da0fa20903a69ae52ab501f30fc5c768dcce31434cd2f55d52addc1a2c0495 emulator-linux_x64-16489710.zip
+                1829806279af5365812cc2d22c9d292a535b2157c99575378d2e8e6ede2704b5 emulator-darwin_x64-16489710.zip
+                c2efd240c708f7f900a100d398faa606cc96ff1b1932805df78b8c4cc272fdd4 emulator-darwin_aarch64-16489710.zip
+                b9c90996c4ebca457e3e5dfd61ed2c74227a6f7ffc3a382db5ced8d37da15cbe emulator-windows_x64-16489710.zip
+              </div>
+            </devsite-expandable>

tests/test_update_android_downloads.py

@@ -90,6 +90,69 @@ def test_repository_xml_cross_validation_matches_stable_and_beta(self) -> None:
             checks,
         )
 
+    def test_emulator_numeric_order_preserves_official_dates_and_downloads(self) -> None:
+        frame = (FIXTURES / "emulator-nonmonotonic-frame.html").read_text(encoding="utf-8")
+        releases, _ = updater.parse_releases(frame, "Android Emulator")
+        self.assertEqual(["37.3.3", "37.3.1"], [updater._version_from_emulator_name(r.name) for r in releases])
+        self.assertEqual(["2026-10-06", "2026-10-07"], [r.date_iso for r in releases])
+        self.assertEqual("emulator-linux_x64-16489710.zip", releases[0].downloads[0].filename)
+        self.assertEqual("a0da0fa20903a69ae52ab501f30fc5c768dcce31434cd2f55d52addc1a2c0495", releases[0].downloads[0].checksum)
+        self.assertEqual(4, len(releases[1].downloads))
+
+    def test_emulator_transition_checks_numeric_maximum_per_channel(self) -> None:
+        frame = (FIXTURES / "emulator-nonmonotonic-frame.html").read_text(encoding="utf-8")
+        high, low = updater.parse_releases(frame, "Android Emulator")[0]
+        stable = replace(high, name="Android Emulator (37.2.12) Stable", channel="stable")
+        # Unsorted old pages and a newer publication date cannot mask rollback.
+        old = [low, high, stable]
+        updater._validate_transition(old, [high, low, stable], "Android Emulator")
+        advanced = replace(stable, name="Android Emulator (38.0.0) Stable")
+        for new in ([low, advanced], [advanced], [high, low]):
+            with self.subTest(new=new), self.assertRaises(updater.UpdateError):
+                updater._validate_transition(old, new, "Android Emulator")
+        # A date correction on the same revision is not a binary downgrade.
+        corrected = replace(high, date_iso="2026-10-05")
+        updater._validate_transition(old, [corrected, low, stable], "Android Emulator")
+        advanced_canary = replace(high, name="Android Emulator (37.3.10) Canary", date_iso="2026-10-05", date_display="Oct 05, 2026")
+        updater._validate_transition(old, [advanced_canary, low, stable], "Android Emulator")
+        nine = replace(high, name="Android Emulator (37.3.9) Canary")
+        numeric_frame = updater.render_releases("emulator", [nine, advanced_canary])
+        ordered, _ = updater.parse_releases(numeric_frame, "Android Emulator", True)
+        self.assertEqual(advanced_canary, ordered[0])
+
+    def test_nonmonotonic_emulator_update_is_idempotent_and_rollback_writes_nothing(self) -> None:
+        sources = updater.load_sources(True, ROOT / "scripts" / "update_android_downloads.py")
+        frame = (FIXTURES / "emulator-nonmonotonic-frame.html").read_text(encoding="utf-8")
+        with tempfile.TemporaryDirectory() as temporary_dir:
+            site = Path(temporary_dir)
+            for filename, marker_names in (
+                ("android-studio.html", ["studio"]),
+                ("android-emulator.html", ["emulator"]),
+                ("index.html", ["studio-summary", "emulator-summary"]),
+            ):
+                parts = []
+                for name in marker_names:
+                    product = "studio" if name.startswith("studio") else "emulator"
+                    releases, _ = updater.parse_releases(sources[0 if product == "studio" else 1], "Android " + ("Studio" if product == "studio" else "Emulator"))
+                    start, end = updater.MARKERS[name]
+                    parts.append(start + "\n" + updater.render_releases(product, releases) + "\n" + end)
+                (site / filename).write_text("\n".join(parts), encoding="utf-8")
+            with patch.object(updater, "load_sources", return_value=(sources[0], frame + sources[1], sources[2], sources[3])):
+                report = updater.run_update(site, "write", True, ROOT / "scripts" / "update_android_downloads.py")
+                snapshot = {name: (site / name).read_bytes() for name in updater.TARGET_FILES}
+                again = updater.run_update(site, "write", True, ROOT / "scripts" / "update_android_downloads.py")
+            self.assertEqual("Android Emulator (37.3.3) Canary", report["emulator"]["latest"])
+            self.assertFalse(again["changed"])
+            for name in ("index.html", "android-emulator.html"):
+                page = snapshot[name].decode()
+                self.assertLess(page.index("37.3.3"), page.index("37.3.1"))
+            low = updater.parse_releases(frame, "Android Emulator")[0][1]
+            rollback_frame = updater.render_releases("emulator", [low]).replace('<devsite-expandable ', '<devsite-expandable class="expandable" ')
+            with patch.object(updater, "load_sources", return_value=(sources[0], rollback_frame + sources[1], sources[2], sources[3])):
+                with self.assertRaises(updater.UpdateError):
+                    updater.run_update(site, "write", True, ROOT / "scripts" / "update_android_downloads.py")
+            self.assertEqual(snapshot, {name: (site / name).read_bytes() for name in updater.TARGET_FILES})
+
     def test_repository_newer_beta_rollout_is_reported_without_failing(self) -> None:
         releases, _ = updater.parse_releases(self.emulator_frame, "Android Emulator")
         newer_repository_xml = self.repository_xml.replace(