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Differential D4563

localrepo: create new function for instantiating a local repo object
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Authored by indygreg on Sep 13 2018, 12:29 PM.

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rHGbfeab472e3c0: localrepo: create new function for instantiating a local repo object
Summary

Today, there is a single local repository class - localrepository. Its
init is responsible for loading the .hg/requires file and taking
different actions depending on what is present.

In addition, extensions may define a "reposetup" function that
monkeypatches constructed repository instances, often by implementing
a derived type and changing the class of the repo instance.

Work around alternate storage backends and partial clone has made it
clear to me that shoehorning all this logic into init and operating
on an existing instance is too convoluted. For example, localrepository
assumes revlog storage and swapping in non-revlog storage requires
overriding e.g. file() to return something that isn't a revlog. I've
authored various patches that either:

a) teach various methods (like file()) about different states and

taking the appropriate code path at run-time

b) create methods/attributes/callables used for instantiating things

and populating these in __init__

"a" incurs run-time performance penalties and makes code more
complicated since various functions have a bunch of "if storage is X"
branches.

"b" makes localrepository quickly explode in complexity.

My plan for tackling this problem is to make the local repository type
more dynamic. Instead of a static localrepository class/type that
supports all of the local repository configurations (revlogs vs other,
revlogs with ellipsis, revlog v1 versus revlog v2, etc), we'll
dynamically construct a type providing the implementations that are
needed for the repository on disk, derived from the .hg/requires file
and configuration options. The constructed repository type will be
specialized and methods won't need to be taught about different
implementations nor overloaded.

We may also leverage this functionality for building types that don't
implement all attributes. For example, the "intents" feature allows
commands to declare that they are read only. By dynamically
constructing a repository type, we could return a repository instance
with no attributes related to mutating the repository. This could
include things like a "changelog" property implementation that doesn't
check whether it needs to invalidate the hidden revisions set on every
access.

This commit establishes a function for building a local repository
instance. Future commits will start moving functionality from
localrepository.init to this function. Then we'll start dynamically
changing the returned type depending on options that are present.

This change may seem radical. But it should be fully compatible with
the reposetup() model - at least for now.

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.

Revision Contents
Changeset List

PathPackages
Mmercurial/localrepo.py (14 lines)
Mtests/test-check-interfaces.py (2 lines)

Diff 11161

mercurial/localrepo.py

# the ability to load repositories with custom requirements. Only # the ability to load repositories with custom requirements. Only
# functions defined in loaded extensions are called. # functions defined in loaded extensions are called.
# #
# The function receives a set of requirement strings that the repository # The function receives a set of requirement strings that the repository
# is capable of opening. Functions will typically add elements to the # is capable of opening. Functions will typically add elements to the
# set to reflect that the extension knows how to handle that requirements. # set to reflect that the extension knows how to handle that requirements.
featuresetupfuncs = set() featuresetupfuncs = set()
def makelocalrepository(ui, path, intents=None):
"""Create a local repository object.
Given arguments needed to construct a local repository, this function
derives a type suitable for representing that repository and returns an
instance of it.
The returned object conforms to the ``repository.completelocalrepository``
interface.
"""
return localrepository(ui, path, intents=intents)
@interfaceutil.implementer(repository.completelocalrepository) @interfaceutil.implementer(repository.completelocalrepository)
class localrepository(object): class localrepository(object):
# obsolete experimental requirements: # obsolete experimental requirements:
# - manifestv2: An experimental new manifest format that allowed # - manifestv2: An experimental new manifest format that allowed
# for stem compression of long paths. Experiment ended up not # for stem compression of long paths. Experiment ended up not
# being successful (repository sizes went up due to worse delta # being successful (repository sizes went up due to worse delta
# chains), and the code was deleted in 4.6. # chains), and the code was deleted in 4.6.
assert name.startswith('journal') assert name.startswith('journal')
return os.path.join(base, name.replace('journal', 'undo', 1)) return os.path.join(base, name.replace('journal', 'undo', 1))
def instance(ui, path, create, intents=None, createopts=None): def instance(ui, path, create, intents=None, createopts=None):
localpath = util.urllocalpath(path) localpath = util.urllocalpath(path)
if create: if create:
createrepository(ui, localpath, createopts=createopts) createrepository(ui, localpath, createopts=createopts)
return localrepository(ui, localpath, intents=intents) return makelocalrepository(ui, localpath, intents=intents)
def islocal(path): def islocal(path):
return True return True
def newreporequirements(ui, createopts=None): def newreporequirements(ui, createopts=None):
"""Determine the set of requirements for a new local repository. """Determine the set of requirements for a new local repository.
Extensions can wrap this function to specify custom requirements for Extensions can wrap this function to specify custom requirements for

tests/test-check-interfaces.py

ziverify.verifyClass(repository.ipeerbase, statichttprepo.statichttppeer) ziverify.verifyClass(repository.ipeerbase, statichttprepo.statichttppeer)
checkzobject(statichttprepo.statichttppeer(dummyrepo())) checkzobject(statichttprepo.statichttppeer(dummyrepo()))
ziverify.verifyClass(repository.ipeerbase, unionrepo.unionpeer) ziverify.verifyClass(repository.ipeerbase, unionrepo.unionpeer)
checkzobject(unionrepo.unionpeer(dummyrepo())) checkzobject(unionrepo.unionpeer(dummyrepo()))
ziverify.verifyClass(repository.completelocalrepository, ziverify.verifyClass(repository.completelocalrepository,
localrepo.localrepository) localrepo.localrepository)
repo = localrepo.localrepository(ui, rootdir) repo = localrepo.makelocalrepository(ui, rootdir)
checkzobject(repo) checkzobject(repo)
ziverify.verifyClass(wireprototypes.baseprotocolhandler, ziverify.verifyClass(wireprototypes.baseprotocolhandler,
wireprotoserver.sshv1protocolhandler) wireprotoserver.sshv1protocolhandler)
ziverify.verifyClass(wireprototypes.baseprotocolhandler, ziverify.verifyClass(wireprototypes.baseprotocolhandler,
wireprotoserver.sshv2protocolhandler) wireprotoserver.sshv2protocolhandler)
ziverify.verifyClass(wireprototypes.baseprotocolhandler, ziverify.verifyClass(wireprototypes.baseprotocolhandler,
wireprotoserver.httpv1protocolhandler) wireprotoserver.httpv1protocolhandler)