Page MenuHomePhabricator

namespaces: let namespaces override singlenode() definition
ClosedPublic

Authored by martinvonz on Jun 28 2018, 1:13 AM.

Details

Summary

Some namespaces have multiple nodes per name (meaning that their
namemap() returns multiple nodes). One such namespace is the "topics"
namespace (from the evolve repo). We also have our own internal
namespace at Google (for review units) that has multiple nodes per
name. These namespaces may not want to use the default "pick highest
revnum" resolution that we currently use when resolving a name to a
single node. As an example, they may decide that hg co <name> should
check out a commit that's last in some sense even if an earlier commit
had just been amended and thus had a higher revnum [1]. This patch
gives the namespace the option to continue to return multiple nodes
and to override how the best node is picked. Allowing namespaces to
override that may also be useful as an optimization (it may be cheaper
for the namespace to find just that node).

I have been arguing (in D3715) for using all the nodes returned from
namemap() when resolving the symbol to a revset, so e.g. `hg log -r
stable` would resolve to *all* nodes on stable, not just the one with
the highest revnum (except that I don't actually think we should
change it for the branch namespace because of BC). Most people seem
opposed to that. If we decide not to do it, I think we can deprecate
the namemap() function in favor of the new singlenode() (I find it
weird to have namespaces, like the branch namespace, where namemap()
isn't nodemap()'s inverse). I therefore think this patch makes sense
regardless of what we decide on that issue.

[1] Actually, even the branch namespace would have wanted to override

singlenode() if it had supported multiple nodes. That's because
closes branch heads are mostly ignored, so "hg co default" will
not check out the highest-revnum node if that's a closed head.

Diff Detail

Repository
rHG Mercurial
Lint
Automatic diff as part of commit; lint not applicable.
Unit
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

martinvonz created this revision.Jun 28 2018, 1:13 AM
martinvonz updated this revision to Diff 9333.Jun 28 2018, 1:14 AM
yuja added a subscriber: yuja.Jun 28 2018, 8:59 AM

Makes sense. One nit.

+ if not singlenode:
+ def singlenode(repo, name):
+ n = self.namemap(repo, name)
+ if n:
+ # return max revision number
+ if len(n) > 1:
+ cl = repo.changelog
+ maxrev = max(cl.rev(node) for node in n)
+ return cl.node(maxrev)
+ return n[0]
+ return None
+ self.singlenode = singlenode

The default implementation has to be defined as an unbound method to avoid
reference cycle: self.singlenode -> singlenode -> self.

martinvonz updated this revision to Diff 9336.Jun 28 2018, 10:24 AM
In D3852#60160, @yuja wrote:

Makes sense. One nit.

+ if not singlenode:
+ def singlenode(repo, name):
+ n = self.namemap(repo, name)
+ if n:
+ # return max revision number
+ if len(n) > 1:
+ cl = repo.changelog
+ maxrev = max(cl.rev(node) for node in n)
+ return cl.node(maxrev)
+ return n[0]
+ return None
+ self.singlenode = singlenode

The default implementation has to be defined as an unbound method to avoid
reference cycle: self.singlenode -> singlenode -> self.

Done

This revision was automatically updated to reflect the committed changes.