hooks: add .arcconfig change blocking hook for conduit-testing re…

…pos (Bug 1789686) r=grammar,zeid

Adds a hook to check that changes to `.arcconfig` files in
`conduit-testing` repos do not revert the file from pointing
to the dev Phabricator server.

Differential Revision: https://phabricator.services.mozilla.com/D157342

--HG--
extra : moz-landing-system : lando

hghooks/mozhghooks/check/prevent_conduit_arcconfig.py

@@ -0,0 +1,65 @@
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+import json
+
+from mercurial import error
+
+from ..checks import (
+    PreTxnChangegroupCheck,
+    print_banner,
+)
+
+
+REJECT_MESSAGE = b"""
+Push contains unwanted changes to `.arcconfig` files.
+
+Please ensure `.arcconfig` points to the Phab dev server for
+`conduit-testing` repos.
+"""
+
+ARCCONFIG_PATH = b".arcconfig"
+
+DEV_PHAB_URL = "https://phabricator-dev.allizom.org/"
+
+
+class PreventConduitArcconfig(PreTxnChangegroupCheck):
+    """Prevent `.arcconfig` updates for `conduit-testing` repos."""
+
+    @property
+    def name(self):
+        return b"prevent_conduit_arcconfig"
+
+    def relevant(self) -> bool:
+        return b"conduit-testing" in self.repo.root.split(b"/")
+
+    def pre(self, _node):
+        self.latest_arcconfig_contents = ""
+
+    def check(self, ctx) -> bool:
+        if ARCCONFIG_PATH in ctx.files():
+            fctx = ctx[ARCCONFIG_PATH]
+            self.latest_arcconfig_contents = fctx.data().decode("utf-8")
+
+        return True
+
+    def post_check(self) -> bool:
+        if not self.latest_arcconfig_contents:
+            # No updates to `.arcconfig`.
+            return True
+
+        try:
+            arcconfig = json.loads(self.latest_arcconfig_contents)
+        except json.JSONDecodeError as exc:
+            raise error.Abort(b"Could not decode `.arcconfig` to JSON.") from exc
+
+        if arcconfig["phabricator.uri"].startswith(DEV_PHAB_URL):
+            # Latest state of `.arcconfig` maintains dev URL.
+            return True
+
+        # `.arcconfig` has been updated to point to the wrong server (prod).
+        print_banner(self.ui, b"error", REJECT_MESSAGE)
+        return False
+

hghooks/mozhghooks/extension.py

@@ -53,6 +53,7 @@ def get_check_classes(hook):
         merge_day,
         prevent_cross_channel_messages,
         check_bug_references,
+        prevent_conduit_arcconfig,
         prevent_subrepos,
         prevent_symlinks,
         prevent_sync_ipc_changes,
@@ -67,6 +68,7 @@ def get_check_classes(hook):
     if hook == b'pretxnchangegroup':
         return (
             merge_day.MergeDayCheck,
+            prevent_conduit_arcconfig.PreventConduitArcconfig,
             prevent_cross_channel_messages.XChannelMessageCheck,
             prevent_subrepos.PreventSubReposCheck,
             prevent_symlinks.PreventSymlinksCheck,

hghooks/tests/test-prevent-arcconfig.t

@@ -0,0 +1,70 @@
+  $ . $TESTDIR/hghooks/tests/common.sh
+
+`conduit-testing` repos should only allow the dev phab server in `.arcconfig`.
+
+  $ hg init conduit-testing
+  $ configurehooks conduit-testing
+  $ hg -q clone conduit-testing client
+  $ cd client
+  $ echo '{"phabricator.uri":"https://phabricator-dev.allizom.org/"}' > .arcconfig
+  $ hg ci -q -A -m "add .arcconfig"
+  $ hg push
+  pushing to $TESTTMP/conduit-testing
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files
+
+  $ echo '{"phabricator.uri":"https://phabricator.services.mozilla.com/"}' > .arcconfig
+  $ hg ci -q -A -m "update .arcconfig to bad value"
+  $ hg push
+  pushing to $TESTTMP/conduit-testing
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+
+  ************************** ERROR ***************************
+  Push contains unwanted changes to `.arcconfig` files.
+
+  Please ensure `.arcconfig` points to the Phab dev server for
+  `conduit-testing` repos.
+  ************************************************************
+
+  transaction abort!
+  rollback completed
+  abort: pretxnchangegroup.mozhooks hook failed
+  [255]
+
+Pushes that update `.arcconfig` and then revert it should be allowed.
+
+  $ echo '{"phabricator.uri":"https://phabricator-dev.allizom.org/"}' > .arcconfig
+  $ hg ci -q -A -m "revert .arcconfig to correct value"
+  $ hg log -G
+  @  changeset:   2:743d41d3d1de
+  |  tag:         tip
+  |  user:        test
+  |  date:        Thu Jan 01 00:00:00 1970 +0000
+  |  summary:     revert .arcconfig to correct value
+  |
+  o  changeset:   1:dcd947bcda7b
+  |  user:        test
+  |  date:        Thu Jan 01 00:00:00 1970 +0000
+  |  summary:     update .arcconfig to bad value
+  |
+  o  changeset:   0:58f2675adc14
+     user:        test
+     date:        Thu Jan 01 00:00:00 1970 +0000
+     summary:     add .arcconfig
+
+  $ hg push
+  pushing to $TESTTMP/conduit-testing
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 2 changesets with 2 changes to 1 files
+
+  $ cd ..
+