Isolate manual artifact validation without package publication

scripts/check-upstream-releases.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+"""Plan stable releases. HTTP/network errors fail closed; only 404 means absent."""
+import argparse, json, re, urllib.request, urllib.error
+from pathlib import Path
+
+def get(url):
+    for attempt in range(3):
+        try:
+            with urllib.request.urlopen(url, timeout=45) as response:
+                return json.load(response)
+        except urllib.error.HTTPError as error:
+            if error.code == 404:
+                return None
+            if error.code < 500 and error.code != 429:
+                raise
+            if attempt == 2:
+                raise
+        except (OSError, TimeoutError):
+            if attempt == 2:
+                raise
+    raise RuntimeError("Unreachable")
+
+def plan(config, upstream, published, force=False):
+    result = []
+    for entry in config["branches"]:
+        major = entry["major"]
+        candidates = [v for v in upstream if re.fullmatch(r"\d+\.\d+\.\d+", v)
+                      and int(v.split(".")[0]) == major]
+        version = entry.get("fixed_version") or max(candidates, key=lambda v: tuple(map(int, v.split("."))))
+        package = f"{version}-{entry['angle_branch']}.{entry['revision']}"
+        if entry.get("daily", True) and (force or package.lower() not in {v.lower() for v in published}):
+            result.append({"ref": entry["ref"], "skiasharp_version": version, "package_version": package})
+    return result
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--config", default="build/release-tracks.json")
+    parser.add_argument("--output", default="release-plan.json")
+    parser.add_argument("--force", action="store_true")
+    args = parser.parse_args()
+    upstream = get("https://api.nuget.org/v3-flatcontainer/skiasharp/index.json")
+    published = get("https://api.nuget.org/v3-flatcontainer/staticlink.avalonia/index.json")
+    if upstream is None:
+        raise SystemExit("SkiaSharp package index is missing")
+    result = plan(json.loads(Path(args.config).read_text()), upstream["versions"], (published or {}).get("versions", []), force=args.force)
+    Path(args.output).write_text(json.dumps(result, indent=2) + "\n")
+    print(json.dumps(result))