crosvm.updateScript: use more stable update source

It has been explained to me that cros-omahaproxy reports which
versions are available to users, while cros-updates-serving reports
the latest builds available for each channel.  The latter is probably
better for our use case anyway, and apparently, while both aren't
officially supported, is less likely to randomly break.

So let's use that instead, even if it is much more annoying to parse.

1 files changed, 18 insertions, 12 deletions

diff --git a/pkgs/applications/virtualization/crosvm/update.py b/pkgs/applications/virtualization/crosvm/update.py
index d00bffce3b8..280d6ec1811 100755
--- a/pkgs/applications/virtualization/crosvm/update.py
+++ b/pkgs/applications/virtualization/crosvm/update.py
@@ -1,15 +1,15 @@
 #! /usr/bin/env nix-shell
-#! nix-shell -p python3 -p nix-prefetch-git -i python
+#! nix-shell -p nix-prefetch-git "python3.withPackages (ps: with ps; [ lxml ])"
+#! nix-shell -i python
 
 import base64
-import csv
 import json
 import re
 import subprocess
-import xml.etree.ElementTree as ElementTree
 from codecs import iterdecode
-from operator import itemgetter
 from os.path import dirname, splitext
+from lxml import etree
+from lxml.etree import HTMLParser
 from urllib.request import urlopen
 
 # ChromiumOS components required to build crosvm.
@@ -27,13 +27,19 @@ buildspecs_url = f'{manifest_versions}/+/refs/heads/master/paladin/buildspecs/'
 # branch branches are used for fixes for specific devices.  So for
 # Chromium OS they will always be 0.  This is a best guess, and is not
 # documented.
-with urlopen('https://cros-omahaproxy.appspot.com/all') as resp:
-    versions = csv.DictReader(iterdecode(resp, 'utf-8'))
-    stables = filter(lambda v: v['track'] == 'stable-channel', versions)
-    stable = sorted(stables, key=itemgetter('chrome_version'), reverse=True)[0]
+with urlopen('https://cros-updates-serving.appspot.com/') as resp:
+    document = etree.parse(resp, HTMLParser())
+    # bgcolor="lightgreen" is set on the most up-to-date version for
+    # each channel, so find a lightgreen cell in the "Stable" column.
+    (platform_version, chrome_version) = document.xpath("""
+        (//table[@id="cros-updates"]/tr/td[1 + count(
+            //table[@id="cros-updates"]/thead/tr[1]/th[text() = "Stable"]
+            /preceding-sibling::*)
+        ][@bgcolor="lightgreen"])[1]/text()
+    """)
 
-chrome_major_version = re.match(r'\d+', stable['chrome_version'])[0]
-chromeos_tip_build = re.match(r'\d+', stable['chromeos_version'])[0]
+chrome_major_version = re.match(r'\d+', chrome_version)[0]
+chromeos_tip_build = re.match(r'\d+', platform_version)[0]
 
 # Find the most recent buildspec for the stable Chrome version and
 # Chromium OS build number.  Its branch build and branch branch build
@@ -52,8 +58,8 @@ revisions = {}
 
 # Read the buildspec, and extract the git revisions for each component.
 with urlopen(f'{buildspecs_url}{chrome_major_version}/{buildspec}.xml?format=TEXT') as resp:
-    xml = base64.decodebytes(resp.read()).decode('utf-8')
-    root = ElementTree.fromstring(xml)
+    xml = base64.decodebytes(resp.read())
+    root = etree.fromstring(xml)
     for project in root.findall('project'):
         revisions[project.get('name')] = project.get('revision')