def parent()

in mozci/push.py [0:0]

• 34 lines of code
• 10 McCabe index (conditional complexity)

    def parent(self):
        """Returns the parent push of this push.

        Returns:
            Push: A `Push` instance representing the parent push.

        Raises:
            :class:`~mozci.errors.ParentPushNotFound`: When no suitable parent
                push can be detected.
        """
        # Mozilla-unified and try allow multiple heads, so we can't rely on
        # `self.id - 1` to be the parent.
        if self.branch not in ("mozilla-unified", "try"):
            return self.create_push(self.id - 1)

        changesets = [c for c in self._hgmo.changesets if c.get("phase") == "draft"]
        if not changesets:
            # Supports mozilla-unified as well as older automationrelevance
            # files that don't contain the phase.
            changesets = self._hgmo.changesets

        parents = changesets[0]["parents"]
        if len(parents) > 1:
            raise ParentPushNotFound(
                "merge commits are unsupported", rev=self.rev, branch=self.branch
            )

        # Search for this revision in the following repositories. We search
        # autoland last as it would run the fewest tasks, so a push from one of
        # the other repositories would be preferable.
        branches = ("mozilla-central", "mozilla-beta", "mozilla-release", "autoland")
        found_on = []
        parent_rev = parents[0]
        for branch in branches:
            try:
                hgmo = HgRev.create(parent_rev, branch=branch)
                head = hgmo.pushhead
            except PushNotFound:
                continue

            found_on.append(branch)

            # Revision exists in repo but is not the 'pushhead', so keep searching.
            if head != parent_rev:
                continue

            return Push(parent_rev, branch=branch)

        if found_on:
            branches = found_on
            reason = "was not a push head"
        else:
            # This should be extremely rare (if not impossible).
            reason = "was not found"

        branches = [
            b[len("mozilla-") :] if b.startswith("mozilla-") else b for b in branches
        ]
        msg = f"parent revision '{parent_rev[:12]}' {reason} on any of {', '.join(branches)}"
        raise ParentPushNotFound(msg, rev=self.rev, branch=self.branch)