Mercurial > hg
view mercurial/registrar.py @ 29375:fcaf20175b1b
demandimport: delay loading for "from a import b" with absolute_import
Before this patch, "from a import b" doesn't delay loading module "b",
if absolute_import is enabled, even though "from . import b" does.
For example:
- it is assumed that extension X has "from P import M" for module M
under package P with absolute_import feature
- if importing module M is already delayed before loading extension
X, loading module M in extension X is delayed until actually
referring
util, cmdutil, scmutil or so of Mercurial itself should be
imported by "from . import M" style before loading extension X
- otherwise, module M is loaded immediately at loading extension X,
even if extension X itself isn't used at that "hg" command invocation
Some minor modules (e.g. filemerge or so) of Mercurial itself
aren't imported by "from . import M" style before loading
extension X. And of course, external libraries aren't, too.
This might cause startup performance problem of hg command, because
many bundled extensions already enable absolute_import feature.
To delay loading module for "from a import b" with absolute_import
feature, this patch does below in "from a (or .a) import b" with
absolute_import case:
1. import root module of "name" by system built-in __import__
(referred as _origimport)
2. recurse down the module chain for hierarchical "name"
This logic can be shared with non absolute_import
case. Therefore, this patch also centralizes it into chainmodules().
3. and fall through to process elements in "fromlist" for the leaf
module of "name"
Processing elements in "fromlist" is executed in the code path
after "if _pypy: .... else: ..." clause. Therefore, this patch
replaces "if _pypy:" with "elif _pypy:" to share it.
At 4f1144c3c72b introducing original "work around" for "from a import
b" case, elements in "fromlist" were imported with "level=level". But
"level" might be grater than 1 (e.g. level=2 in "from .. import b"
case) at demandimport() invocation, and importing direct sub-module in
"fromlist" with level grater than 1 causes unexpected result.
IMHO, this seems main reason of "errors for unknown reason" described
in 4f1144c3c72b, and we don't have to worry about it, because this
issue was already fixed by 78d05778907b.
This is reason why this patch removes "errors for unknown reasons"
comment.
author | FUJIWARA Katsunori <foozy@lares.dti.ne.jp> |
---|---|
date | Sun, 19 Jun 2016 02:17:33 +0900 |
parents | cc103bd0dbf9 |
children | 91a95ad985d8 |
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line source
# 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 ( util, ) class _funcregistrarbase(object): """Base of decorator to register a fuction 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 func.__doc__ and not util.safehasattr(func, '_origdoc'): doc = func.__doc__.strip() func._origdoc = doc func.__doc__ = 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 """ pass 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). '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): func._safe = safe 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:: templaetkeyword = registrar.templatekeyword() @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. '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. """ class templatefilter(_templateregistrarbase): """Decorator to register template filer Usage:: templatefilter = registrar.templatefilter() @templatefilter('myfilter') def myfilterfunc(text): '''Explanation of this template filter .... ''' pass The first string argument is used also in online help. '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. """ class templatefunc(_templateregistrarbase): """Decorator to register template function Usage:: templatefunc = registrar.templatefunc() @templatefunc('myfunc(arg1, arg2[, arg3])') def myfuncfunc(context, mapping, args): '''Explanation of this template function .... ''' pass The first string argument is used also in online help. '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 'templater.loadfunction()' is needed. """ _getname = _funcregistrarbase._parsefuncdecl