Mercurial > hg-stable
view mercurial/registrar.py @ 37716:dfc51a482031
registrar: replace "cmdtype" with an intent-based mechanism (API)
Commands perform varied actions and repositories vary in their
capabilities.
Historically, the .hg/requires file has been used to lock out clients
lacking a requirement. But this is a very heavy-handed approach and
is typically reserved for cases where the on-disk storage format
changes and we want to prevent incompatible clients from operating on
a repo.
Outside of the .hg/requires file, we tend to deal with things like
optional, extension-provided features via checking at call sites.
We'll either have checks in core or extensions will monkeypatch
functions in core disabling incompatible features, enabling new
features, etc.
Things are somewhat tolerable today. But once we introduce alternate
storage backends with varying support for repository features and
vastly different modes of behavior, the current model will quickly
grow unwieldy. For example, the implementation of the "simple store"
required a lot of hacks to deal with stripping and verify because
various parts of core assume things are implemented a certain way.
Partial clone will require new ways of modeling file data retrieval,
because we can no longer assume that all file data is already local.
In this new world, some commands might not make any sense for certain
types of repositories.
What we need is a mechanism to affect the construction of repository
(and eventually peer) instances so the requirements/capabilities
needed for the current operation can be taken into account. "Current
operation" can almost certainly be defined by a command. So it makes
sense for commands to declare their intended actions.
This commit introduces the "intents" concept on the command registrar.
"intents" captures a set of strings that declare actions that are
anticipated to be taken, requirements the repository must possess, etc.
These intents will be passed into hg.repo(), which will pass them into
localrepository, where they can be used to influence the object being
created. Some use cases for this include:
* For read-only intents, constructing a repository object that doesn't
expose methods that can mutate the repository. Its VFS instances
don't even allow opening a file with write access.
* For read-only intents, constructing a repository object without
cache invalidation logic. If the repo never changes during its lifetime,
nothing ever needs to be invalidated and we don't need to do expensive
things like verify the changelog's hidden revisions state is accurate
every time we access repo.changelog.
* We can automatically hide commands from `hg help` when the current
repository doesn't provide that command. For example, an alternate
storage backend may not support `hg commit`, so we can hide that
command or anything else that would perform local commits.
We already kind of had an "intents" mechanism on the registrar in the
form of "cmdtype." However, it was never used. And it was limited to
a single value. We really need something that supports multiple
intents. And because intents may be defined by extensions and at this
point are advisory, I think it is best to define them in a set rather
than as separate arguments/attributes on the command.
Differential Revision: https://phab.mercurial-scm.org/D3376
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Sat, 14 Apr 2018 09:23:48 -0700 |
parents | 9bcf096a2da2 |
children | aa98392eb5b0 |
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# registrar.py - utilities to register function for specific purpose # # Copyright FUJIWARA Katsunori <foozy@lares.dti.ne.jp> and others # # 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 from . import ( configitems, error, pycompat, util, ) # unlike the other registered items, config options are neither functions or # classes. Registering the option is just small function call. # # We still add the official API to the registrar module for consistency with # the other items extensions want might to register. configitem = configitems.getitemregister class _funcregistrarbase(object): """Base of decorator to register a function for specific purpose This decorator stores decorated functions into own dict 'table'. The least derived class can be defined by overriding 'formatdoc', for example:: class keyword(_funcregistrarbase): _docformat = ":%s: %s" This should be used as below: keyword = registrar.keyword() @keyword('bar') def barfunc(*args, **kwargs): '''Explanation of bar keyword .... ''' pass In this case: - 'barfunc' is stored as 'bar' in '_table' of an instance 'keyword' above - 'barfunc.__doc__' becomes ":bar: Explanation of bar keyword" """ def __init__(self, table=None): if table is None: self._table = {} else: self._table = table def __call__(self, decl, *args, **kwargs): return lambda func: self._doregister(func, decl, *args, **kwargs) def _doregister(self, func, decl, *args, **kwargs): name = self._getname(decl) if name in self._table: msg = 'duplicate registration for name: "%s"' % name raise error.ProgrammingError(msg) if func.__doc__ and not util.safehasattr(func, '_origdoc'): doc = pycompat.sysbytes(func.__doc__).strip() func._origdoc = doc func.__doc__ = pycompat.sysstr(self._formatdoc(decl, doc)) self._table[name] = func self._extrasetup(name, func, *args, **kwargs) return func def _parsefuncdecl(self, decl): """Parse function declaration and return the name of function in it """ i = decl.find('(') if i >= 0: return decl[:i] else: return decl def _getname(self, decl): """Return the name of the registered function from decl Derived class should override this, if it allows more descriptive 'decl' string than just a name. """ return decl _docformat = None def _formatdoc(self, decl, doc): """Return formatted document of the registered function for help 'doc' is '__doc__.strip()' of the registered function. """ return self._docformat % (decl, doc) def _extrasetup(self, name, func): """Execute exra setup for registered function, if needed """ class command(_funcregistrarbase): """Decorator to register a command function to table This class receives a command table as its argument. The table should be a dict. The created object can be used as a decorator for adding commands to that command table. This accepts multiple arguments to define a command. The first argument is the command name (as bytes). The `options` keyword argument is an iterable of tuples defining command arguments. See ``mercurial.fancyopts.fancyopts()`` for the format of each tuple. The `synopsis` argument defines a short, one line summary of how to use the command. This shows up in the help output. There are three arguments that control what repository (if any) is found and passed to the decorated function: `norepo`, `optionalrepo`, and `inferrepo`. The `norepo` argument defines whether the command does not require a local repository. Most commands operate against a repository, thus the default is False. When True, no repository will be passed. The `optionalrepo` argument defines whether the command optionally requires a local repository. If no repository can be found, None will be passed to the decorated function. The `inferrepo` argument defines whether to try to find a repository from the command line arguments. If True, arguments will be examined for potential repository locations. See ``findrepo()``. If a repository is found, it will be used and passed to the decorated function. The `intents` argument defines a set of intended actions or capabilities the command is taking. These intents can be used to affect the construction of the repository object passed to the command. For example, commands declaring that they are read-only could receive a repository that doesn't have any methods allowing repository mutation. Other intents could be used to prevent the command from running if the requested intent could not be fulfilled. The following intents are defined: readonly The command is read-only The signature of the decorated function looks like this: def cmd(ui[, repo] [, <args>] [, <options>]) `repo` is required if `norepo` is False. `<args>` are positional args (or `*args`) arguments, of non-option arguments from the command line. `<options>` are keyword arguments (or `**options`) of option arguments from the command line. See the WritingExtensions and MercurialApi documentation for more exhaustive descriptions and examples. """ def _doregister(self, func, name, options=(), synopsis=None, norepo=False, optionalrepo=False, inferrepo=False, intents=None): func.norepo = norepo func.optionalrepo = optionalrepo func.inferrepo = inferrepo func.intents = intents or set() if synopsis: self._table[name] = func, list(options), synopsis else: self._table[name] = func, list(options) return func INTENT_READONLY = b'readonly' class revsetpredicate(_funcregistrarbase): """Decorator to register revset predicate Usage:: revsetpredicate = registrar.revsetpredicate() @revsetpredicate('mypredicate(arg1, arg2[, arg3])') def mypredicatefunc(repo, subset, x): '''Explanation of this revset predicate .... ''' pass The first string argument is used also in online help. Optional argument 'safe' indicates whether a predicate is safe for DoS attack (False by default). Optional argument 'takeorder' indicates whether a predicate function takes ordering policy as the last argument. Optional argument 'weight' indicates the estimated run-time cost, useful for static optimization, default is 1. Higher weight means more expensive. Usually, revsets that are fast and return only one revision has a weight of 0.5 (ex. a symbol); revsets with O(changelog) complexity and read only the changelog have weight 10 (ex. author); revsets reading manifest deltas have weight 30 (ex. adds); revset reading manifest contents have weight 100 (ex. contains). Note: those values are flexible. If the revset has a same big-O time complexity as 'contains', but with a smaller constant, it might have a weight of 90. 'revsetpredicate' instance in example above can be used to decorate multiple functions. Decorated functions are registered automatically at loading extension, if an instance named as 'revsetpredicate' is used for decorating in extension. Otherwise, explicit 'revset.loadpredicate()' is needed. """ _getname = _funcregistrarbase._parsefuncdecl _docformat = "``%s``\n %s" def _extrasetup(self, name, func, safe=False, takeorder=False, weight=1): func._safe = safe func._takeorder = takeorder func._weight = weight class filesetpredicate(_funcregistrarbase): """Decorator to register fileset predicate Usage:: filesetpredicate = registrar.filesetpredicate() @filesetpredicate('mypredicate()') def mypredicatefunc(mctx, x): '''Explanation of this fileset predicate .... ''' pass The first string argument is used also in online help. Optional argument 'callstatus' indicates whether a predicate implies 'matchctx.status()' at runtime or not (False, by default). Optional argument 'callexisting' indicates whether a predicate implies 'matchctx.existing()' at runtime or not (False, by default). 'filesetpredicate' instance in example above can be used to decorate multiple functions. Decorated functions are registered automatically at loading extension, if an instance named as 'filesetpredicate' is used for decorating in extension. Otherwise, explicit 'fileset.loadpredicate()' is needed. """ _getname = _funcregistrarbase._parsefuncdecl _docformat = "``%s``\n %s" def _extrasetup(self, name, func, callstatus=False, callexisting=False): func._callstatus = callstatus func._callexisting = callexisting class _templateregistrarbase(_funcregistrarbase): """Base of decorator to register functions as template specific one """ _docformat = ":%s: %s" class templatekeyword(_templateregistrarbase): """Decorator to register template keyword Usage:: templatekeyword = registrar.templatekeyword() # new API (since Mercurial 4.6) @templatekeyword('mykeyword', requires={'repo', 'ctx'}) def mykeywordfunc(context, mapping): '''Explanation of this template keyword .... ''' pass # old API @templatekeyword('mykeyword') def mykeywordfunc(repo, ctx, templ, cache, revcache, **args): '''Explanation of this template keyword .... ''' pass The first string argument is used also in online help. Optional argument 'requires' should be a collection of resource names which the template keyword depends on. This also serves as a flag to switch to the new API. If 'requires' is unspecified, all template keywords and resources are expanded to the function arguments. 'templatekeyword' instance in example above can be used to decorate multiple functions. Decorated functions are registered automatically at loading extension, if an instance named as 'templatekeyword' is used for decorating in extension. Otherwise, explicit 'templatekw.loadkeyword()' is needed. """ def _extrasetup(self, name, func, requires=None): func._requires = requires class templatefilter(_templateregistrarbase): """Decorator to register template filer Usage:: templatefilter = registrar.templatefilter() @templatefilter('myfilter', intype=bytes) def myfilterfunc(text): '''Explanation of this template filter .... ''' pass The first string argument is used also in online help. Optional argument 'intype' defines the type of the input argument, which should be (bytes, int, templateutil.date, or None for any.) 'templatefilter' instance in example above can be used to decorate multiple functions. Decorated functions are registered automatically at loading extension, if an instance named as 'templatefilter' is used for decorating in extension. Otherwise, explicit 'templatefilters.loadkeyword()' is needed. """ def _extrasetup(self, name, func, intype=None): func._intype = intype class templatefunc(_templateregistrarbase): """Decorator to register template function Usage:: templatefunc = registrar.templatefunc() @templatefunc('myfunc(arg1, arg2[, arg3])', argspec='arg1 arg2 arg3') def myfuncfunc(context, mapping, args): '''Explanation of this template function .... ''' pass The first string argument is used also in online help. If optional 'argspec' is defined, the function will receive 'args' as a dict of named arguments. Otherwise 'args' is a list of positional arguments. 'templatefunc' instance in example above can be used to decorate multiple functions. Decorated functions are registered automatically at loading extension, if an instance named as 'templatefunc' is used for decorating in extension. Otherwise, explicit 'templatefuncs.loadfunction()' is needed. """ _getname = _funcregistrarbase._parsefuncdecl def _extrasetup(self, name, func, argspec=None): func._argspec = argspec class internalmerge(_funcregistrarbase): """Decorator to register in-process merge tool Usage:: internalmerge = registrar.internalmerge() @internalmerge('mymerge', internalmerge.mergeonly, onfailure=None, precheck=None): def mymergefunc(repo, mynode, orig, fcd, fco, fca, toolconf, files, labels=None): '''Explanation of this internal merge tool .... ''' return 1, False # means "conflicted", "no deletion needed" The first string argument is used to compose actual merge tool name, ":name" and "internal:name" (the latter is historical one). The second argument is one of merge types below: ========== ======== ======== ========= merge type precheck premerge fullmerge ========== ======== ======== ========= nomerge x x x mergeonly o x o fullmerge o o o ========== ======== ======== ========= Optional argument 'onfailure' is the format of warning message to be used at failure of merging (target filename is specified at formatting). Or, None or so, if warning message should be suppressed. Optional argument 'precheck' is the function to be used before actual invocation of internal merge tool itself. It takes as same arguments as internal merge tool does, other than 'files' and 'labels'. If it returns false value, merging is aborted immediately (and file is marked as "unresolved"). 'internalmerge' instance in example above can be used to decorate multiple functions. Decorated functions are registered automatically at loading extension, if an instance named as 'internalmerge' is used for decorating in extension. Otherwise, explicit 'filemerge.loadinternalmerge()' is needed. """ _docformat = "``:%s``\n %s" # merge type definitions: nomerge = None mergeonly = 'mergeonly' # just the full merge, no premerge fullmerge = 'fullmerge' # both premerge and merge def _extrasetup(self, name, func, mergetype, onfailure=None, precheck=None): func.mergetype = mergetype func.onfailure = onfailure func.precheck = precheck