1 files changed, 89 insertions, 0 deletions
diff --git a/pkgs/desktops/gnome/find-latest-version.py b/pkgs/desktops/gnome/find-latest-version.py
new file mode 100644
index 00000000000..3078999e3e5
--- /dev/null
+++ b/pkgs/desktops/gnome/find-latest-version.py
@@ -0,0 +1,89 @@
+import argparse
+import math
+import json
+import requests
+import sys
+from libversion import Version
+from typing import Optional
+
+
+def version_to_list(version):
+    return list(map(int, version.split(".")))
+
+
+def odd_unstable(version: Version, selected):
+    try:
+        version = version_to_list(version.value)
+    except:
+        # Failing to parse as a list of numbers likely means the version contains a string tag like “beta”, therefore it is not a stable release.
+        return selected != "stable"
+
+    if len(version) < 2:
+        return True
+
+    even = version[1] % 2 == 0
+    prerelease = (version[1] >= 90 and version[1] < 100) or (version[1] >= 900 and version[1] < 1000)
+    stable = even and not prerelease
+    if selected == "stable":
+        return stable
+    else:
+        return True
+
+
+def tagged(version: Version, selected):
+    if selected == "stable":
+        return not ("alpha" in version.value or "beta" in version.value or "rc" in version.value)
+    else:
+        return True
+
+
+def no_policy(version: Version, selected):
+    return True
+
+
+version_policies = {
+    "odd-unstable": odd_unstable,
+    "tagged": tagged,
+    "none": no_policy,
+}
+
+
+def make_version_policy(version_predicate, selected, upper_bound: Optional[Version]):
+    if not upper_bound:
+        return lambda version: version_predicate(version, selected)
+    else:
+        return lambda version: version_predicate(version, selected) and version < upper_bound
+
+
+parser = argparse.ArgumentParser(description="Find latest version for a GNOME package by crawling their release server.")
+parser.add_argument("package-name", help="Name of the directory in https://ftp.gnome.org/pub/GNOME/sources/ containing the package.")
+parser.add_argument("version-policy", help="Policy determining which versions are considered stable. GNOME packages usually denote stability by alpha/beta/rc tag in the version. For older packages, odd minor versions are unstable but there are exceptions.", choices=version_policies.keys(), nargs="?", default="tagged")
+parser.add_argument("requested-release", help="Most of the time, we will want to update to stable version but sometimes it is useful to test.", choices=["stable", "unstable"], nargs="?", default="stable")
+parser.add_argument("--upper-bound", dest="upper-bound", help="Only look for versions older than this one (useful for pinning dependencies).")
+
+
+if __name__ == "__main__":
+    args = parser.parse_args()
+
+    package_name = getattr(args, "package-name")
+    requested_release = getattr(args, "requested-release")
+    upper_bound = getattr(args, "upper-bound")
+    if upper_bound:
+        upper_bound = Version(upper_bound)
+    version_predicate = version_policies[getattr(args, "version-policy")]
+    version_policy = make_version_policy(version_predicate, requested_release, upper_bound)
+
+    # The structure of cache.json: https://gitlab.gnome.org/Infrastructure/sysadmin-bin/blob/master/ftpadmin#L762
+    cache = json.loads(requests.get(f"https://ftp.gnome.org/pub/GNOME/sources/{package_name}/cache.json").text)
+    if type(cache) != list or cache[0] != 4:
+        print("Unknown format of cache.json file.", file=sys.stderr)
+        sys.exit(1)
+
+    versions = map(Version, cache[2][package_name])
+    versions = sorted(filter(version_policy, versions))
+
+    if len(versions) == 0:
+        print("No versions matched.", file=sys.stderr)
+        sys.exit(1)
+
+    print(versions[-1].value)