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Differential D3852

namespaces: let namespaces override singlenode() definition
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Authored by martinvonz on Jun 28 2018, 1:13 AM.

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rHG4c0683655599: namespaces: let namespaces override singlenode() definition
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.

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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
martinvonz added a comment.Jun 28 2018, 10:25 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

Closed by commit rHG4c0683655599: namespaces: let namespaces override singlenode() definition (authored by martinvonz). · Explain WhyJun 28 2018, 10:39 AM
This revision was automatically updated to reflect the committed changes.

Revision Contents
Changeset List

PathPackages
Mmercurial/namespaces.py (35 lines)

Diff 9336

mercurial/namespaces.py

if namespace.name not in templatekw.keywords: if namespace.name not in templatekw.keywords:
templatekeyword = registrar.templatekeyword(templatekw.keywords) templatekeyword = registrar.templatekeyword(templatekw.keywords)
@templatekeyword(namespace.name, requires={'repo', 'ctx'}) @templatekeyword(namespace.name, requires={'repo', 'ctx'})
def generatekw(context, mapping): def generatekw(context, mapping):
return templatekw.shownames(context, mapping, namespace.name) return templatekw.shownames(context, mapping, namespace.name)
def singlenode(self, repo, name): def singlenode(self, repo, name):
""" """
Return the 'best' node for the given name. Best means the first node Return the 'best' node for the given name. What's best is defined
in the first nonempty list returned by a name-to-nodes mapping function by the namespace's singlenode() function. The first match returned by
in the defined precedence order. a namespace in the defined precedence order is used.
Raises a KeyError if there is no such node. Raises a KeyError if there is no such node.
""" """
for ns, v in self._names.iteritems(): for ns, v in self._names.iteritems():
n = v.namemap(repo, name) n = v.singlenode(repo, name)
if n: if n:
# return max revision number return n
if len(n) > 1:
cl = repo.changelog
maxrev = max(cl.rev(node) for node in n)
return cl.node(maxrev)
return n[0]
raise KeyError(_('no such name: %s') % name) raise KeyError(_('no such name: %s') % name)
class namespace(object): class namespace(object):
"""provides an interface to a namespace """provides an interface to a namespace
Namespaces are basically generic many-to-many mapping between some Namespaces are basically generic many-to-many mapping between some
(namespaced) names and nodes. The goal here is to control the pollution of (namespaced) names and nodes. The goal here is to control the pollution of
jamming things into tags or bookmarks (in extension-land) and to simplify jamming things into tags or bookmarks (in extension-land) and to simplify
'nodemap': function that takes a node and returns a list of names 'nodemap': function that takes a node and returns a list of names
'deprecated': set of names to be masked for ordinary use 'deprecated': set of names to be masked for ordinary use
'builtin': bool indicating if this namespace is supported by core 'builtin': bool indicating if this namespace is supported by core
Mercurial. Mercurial.
""" """
def __init__(self, name, templatename=None, logname=None, colorname=None, def __init__(self, name, templatename=None, logname=None, colorname=None,
logfmt=None, listnames=None, namemap=None, nodemap=None, logfmt=None, listnames=None, namemap=None, nodemap=None,
deprecated=None, builtin=False): deprecated=None, builtin=False, singlenode=None):
"""create a namespace """create a namespace
name: the namespace to be registered (in plural form) name: the namespace to be registered (in plural form)
templatename: the name to use for templating templatename: the name to use for templating
logname: the name to use for log output; if not specified templatename logname: the name to use for log output; if not specified templatename
is used is used
colorname: the name to use for colored log output; if not specified colorname: the name to use for colored log output; if not specified
logname is used logname is used
logfmt: the format to use for (i18n-ed) log output; if not specified logfmt: the format to use for (i18n-ed) log output; if not specified
it is composed from logname it is composed from logname
listnames: function to list all names listnames: function to list all names
namemap: function that inputs a name, output node(s) namemap: function that inputs a name, output node(s)
nodemap: function that inputs a node, output name(s) nodemap: function that inputs a node, output name(s)
deprecated: set of names to be masked for ordinary use deprecated: set of names to be masked for ordinary use
builtin: whether namespace is implemented by core Mercurial builtin: whether namespace is implemented by core Mercurial
singlenode: function that inputs a name, output best node (or None)
""" """
self.name = name self.name = name
self.templatename = templatename self.templatename = templatename
self.logname = logname self.logname = logname
self.colorname = colorname self.colorname = colorname
self.logfmt = logfmt self.logfmt = logfmt
self.listnames = listnames self.listnames = listnames
self.namemap = namemap self.namemap = namemap
self.nodemap = nodemap self.nodemap = nodemap
if singlenode:
self.singlenode = singlenode
# if logname is not specified, use the template name as backup # if logname is not specified, use the template name as backup
if self.logname is None: if self.logname is None:
self.logname = self.templatename self.logname = self.templatename
# if colorname is not specified, just use the logname as a backup # if colorname is not specified, just use the logname as a backup
if self.colorname is None: if self.colorname is None:
self.colorname = self.logname self.colorname = self.logname
return sorted(self.nodemap(repo, node)) return sorted(self.nodemap(repo, node))
def nodes(self, repo, name): def nodes(self, repo, name):
"""method that returns a list of nodes in a namespace that """method that returns a list of nodes in a namespace that
match a given name. match a given name.
""" """
return sorted(self.namemap(repo, name)) return sorted(self.namemap(repo, name))
def singlenode(self, repo, name):
"""returns the best node for the given name
By default, the best node is the node from nodes() with the highest
revision number. It can be overriden by the namespace."""
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