chromium: Extend update.py to automatically update gn

The gn version depends on the channel and new gn versions aren't always
backward compatible. Therefore we should also include it in
upstream-info.json (I've scoped it under "deps" as we'll likely have to
add more like this in the future).

pkgs/applications/networking/browsers/chromium/common.nix

@@ -316,7 +316,12 @@ let
       patchelf --set-rpath "${libGL}/lib:$origRpath" "$chromiumBinary"
     '';
 
-    passthru.updateScript = ./update.py;
+    passthru = {
+      updateScript = ./update.py;
+      chromiumDeps = {
+        gn = gnChromium;
+      };
+    };
   };
 
 # Remove some extraAttrs we supplied to the base attributes already.

pkgs/applications/networking/browsers/chromium/default.nix

@@ -35,26 +35,15 @@ let
     mkChromiumDerivation = callPackage ./common.nix ({
       inherit channel gnome gnomeSupport gnomeKeyringSupport proprietaryCodecs
               cupsSupport pulseSupport useOzone;
-      # TODO: Remove after we can update gn for the stable channel (backward incompatible changes):
       gnChromium = gn.overrideAttrs (oldAttrs: {
-        version = "2020-07-20";
+        inherit (upstream-info.deps.gn) version;
         src = fetchgit {
-          url = "https://gn.googlesource.com/gn";
+          inherit (upstream-info.deps.gn) url rev sha256;
-          rev = "3028c6a426a4aaf6da91c4ebafe716ae370225fe";
-          sha256 = "0h3wf4152zdvrbb0jbj49q6814lfl3rcy5mj8b2pl9s0ahvkbc6q";
         };
       });
     } // lib.optionalAttrs (lib.versionAtLeast upstream-info.version "87") {
       useOzone = true; # YAY: https://chromium-review.googlesource.com/c/chromium/src/+/2382834 \o/
       useVaapi = !stdenv.isAarch64; # TODO: Might be best to not set use_vaapi anymore (default is fine)
-      gnChromium = gn.overrideAttrs (oldAttrs: {
-        version = "2020-08-17";
-        src = fetchgit {
-          url = "https://gn.googlesource.com/gn";
-          rev = "6f13aaac55a977e1948910942675c69f2b4f7a94";
-          sha256 = "01hpma1sllpdx09mvr4d6073sg6zmk6iv44kd3r28khymcj4s251";
-        };
-      });
     });
 
     browser = callPackage ./browser.nix { inherit channel enableWideVine; };

pkgs/applications/networking/browsers/chromium/update.py

@@ -1,13 +1,15 @@
 #! /usr/bin/env nix-shell
-#! nix-shell -i python -p python3 nix
+#! nix-shell -i python -p python3 nix nix-prefetch-git
 
 import csv
 import json
+import re
 import subprocess
 import sys
 
 from codecs import iterdecode
 from collections import OrderedDict
+from datetime import datetime
 from os.path import abspath, dirname
 from urllib.request import urlopen
 
@@ -26,6 +28,30 @@ def nix_prefetch_url(url, algo='sha256'):
     out = subprocess.check_output(['nix-prefetch-url', '--type', algo, url])
     return out.decode('utf-8').rstrip()
 
+def nix_prefetch_git(url, rev):
+    print(f'nix-prefetch-git {url} {rev}')
+    out = subprocess.check_output(['nix-prefetch-git', '--quiet', '--url', url, '--rev', rev])
+    return json.loads(out)
+
+def get_file_revision(revision, file_path):
+    url = f'https://raw.githubusercontent.com/chromium/chromium/{revision}/{file_path}'
+    with urlopen(url) as http_response:
+        return http_response.read()
+
+def get_channel_dependencies(channel):
+    deps = get_file_revision(channel['version'], 'DEPS')
+    gn_pattern = b"'gn_version': 'git_revision:([0-9a-f]{40})'"
+    gn_commit = re.search(gn_pattern, deps).group(1).decode()
+    gn = nix_prefetch_git('https://gn.googlesource.com/gn', gn_commit)
+    return {
+        'gn': {
+            'version': datetime.fromisoformat(gn['date']).date().isoformat(),
+            'url': gn['url'],
+            'rev': gn['rev'],
+            'sha256': gn['sha256']
+        }
+    }
+
 channels = {}
 last_channels = load_json(JSON_PATH)
 
@@ -58,6 +84,8 @@ with urlopen(HISTORY_URL) as resp:
             # the next one.
             continue
 
+        channel['deps'] = get_channel_dependencies(channel)
+
         channels[channel_name] = channel
 
 with open(JSON_PATH, 'w') as out:

pkgs/applications/networking/browsers/chromium/upstream-info.json

@@ -2,16 +2,40 @@
   "stable": {
     "version": "86.0.4240.183",
     "sha256": "1g39i82js7fm4fqb8i66d6xs0kzqjxzi4vzvvwz5y9rkbikcc4ma",
-    "sha256bin64": "1r0dxqsx6j19hgwr3v2sdlb2vd7gb961c4wba4ymd8wy8j8pzly9"
+    "sha256bin64": "1r0dxqsx6j19hgwr3v2sdlb2vd7gb961c4wba4ymd8wy8j8pzly9",
+    "deps": {
+      "gn": {
+        "version": "2020-08-07",
+        "url": "https://gn.googlesource.com/gn",
+        "rev": "e327ffdc503815916db2543ec000226a8df45163",
+        "sha256": "0kvlfj3www84zp1vmxh76x8fdjm9hyk8lkh2vdsidafpmm75fphr"
+      }
+    }
   },
   "beta": {
     "version": "87.0.4280.40",
     "sha256": "07xh76fl257np68way6i5rf64qbvirkfddy7m5gvqb0fzcqd7dp3",
-    "sha256bin64": "1b2z0aqlh28pqrk6dmabxp1d4mvp9iyfmi4kqmns4cdpg0qgaf41"
+    "sha256bin64": "1b2z0aqlh28pqrk6dmabxp1d4mvp9iyfmi4kqmns4cdpg0qgaf41",
+    "deps": {
+      "gn": {
+        "version": "2020-09-09",
+        "url": "https://gn.googlesource.com/gn",
+        "rev": "e002e68a48d1c82648eadde2f6aafa20d08c36f2",
+        "sha256": "0x4c7amxwzxs39grqs3dnnz0531mpf1p75niq7zhinyfqm86i4dk"
+      }
+    }
   },
   "dev": {
     "version": "88.0.4300.0",
     "sha256": "00cfs2rp4h8ybn2snr1d8ygg635hx7q5gv2aqriy1j6f8a1pgh1b",
-    "sha256bin64": "110r1m14h91212nx6pfhn8wkics7wlwx1608l5cqsxxcpvpzl3pv"
+    "sha256bin64": "110r1m14h91212nx6pfhn8wkics7wlwx1608l5cqsxxcpvpzl3pv",
+    "deps": {
+      "gn": {
+        "version": "2020-09-09",
+        "url": "https://gn.googlesource.com/gn",
+        "rev": "e002e68a48d1c82648eadde2f6aafa20d08c36f2",
+        "sha256": "0x4c7amxwzxs39grqs3dnnz0531mpf1p75niq7zhinyfqm86i4dk"
+      }
+    }
   }
 }