Mercurial > hg
view mercurial/demandload.py @ 2320:dbdce3b99988
fix parsing of tags. make parse errors useful. add new tag tests.
old code read every head of .hgtags. delete and recreate of .hgtags gave
new head, but if error in deleted rev, .hgtags had error messages every
time it was parsed. this was very hard to fix, because deleted revs hard
to get back and update, needed merges too.
new code reads .hgtags on every head. advantage is if parse error
happens with new code, is possible to fix them by editing .hgtags on a
head and committing.
NOTE: new code uses binary search of manifest of each head to be fast,
but still much slower than old code. best thing would be to have delete
record stored in filelog so we never touch manifest. could find live
heads directly from filelog. this is more work than i want now.
new tests check for parse of tags on different heads, and inaccessible
heads created by delete and recreate of .hgtags.
author | Vadim Gelfer <vadim.gelfer@gmail.com> |
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date | Thu, 18 May 2006 23:31:12 -0700 |
parents | d01eac5968c6 |
children | a8a7ce1a01a5 |
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'''Demand load modules when used, not when imported.''' __author__ = '''Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com>. This software may be used and distributed according to the terms of the GNU General Public License, incorporated herein by reference.''' # this is based on matt's original demandload module. it is a # complete rewrite. some time, we may need to support syntax of # "import foo as bar". class _importer(object): '''import a module. it is not imported until needed, and is imported at most once per scope.''' def __init__(self, scope, modname, fromlist): '''scope is context (globals() or locals()) in which import should be made. modname is name of module to import. fromlist is list of modules for "from foo import ..." emulation.''' self.scope = scope self.modname = modname self.fromlist = fromlist self.mod = None def module(self): '''import the module if needed, and return.''' if self.mod is None: self.mod = __import__(self.modname, self.scope, self.scope, self.fromlist) del self.modname, self.fromlist return self.mod class _replacer(object): '''placeholder for a demand loaded module. demandload puts this in a target scope. when an attribute of this object is looked up, this object is replaced in the target scope with the actual module. we use __getattribute__ to avoid namespace clashes between placeholder object and real module.''' def __init__(self, importer, target): self.importer = importer self.target = target # consider case where we do this: # demandload(globals(), 'foo.bar foo.quux') # foo will already exist in target scope when we get to # foo.quux. so we remember that we will need to demandload # quux into foo's scope when we really load it. self.later = [] def module(self): return object.__getattribute__(self, 'importer').module() def __getattribute__(self, key): '''look up an attribute in a module and return it. replace the name of the module in the caller\'s dict with the actual module.''' module = object.__getattribute__(self, 'module')() target = object.__getattribute__(self, 'target') importer = object.__getattribute__(self, 'importer') later = object.__getattribute__(self, 'later') if later: demandload(module.__dict__, ' '.join(later)) importer.scope[target] = module return getattr(module, key) class _replacer_from(_replacer): '''placeholder for a demand loaded module. used for "from foo import ..." emulation. semantics of this are different than regular import, so different implementation needed.''' def module(self): importer = object.__getattribute__(self, 'importer') target = object.__getattribute__(self, 'target') return getattr(importer.module(), target) def __call__(self, *args, **kwargs): target = object.__getattribute__(self, 'module')() return target(*args, **kwargs) def demandload(scope, modules): '''import modules into scope when each is first used. scope should be the value of globals() in the module calling this function, or locals() in the calling function. modules is a string listing module names, separated by white space. names are handled like this: foo import foo foo bar import foo, bar foo.bar import foo.bar foo:bar from foo import bar foo:bar,quux from foo import bar, quux foo.bar:quux from foo.bar import quux''' for mod in modules.split(): col = mod.find(':') if col >= 0: fromlist = mod[col+1:].split(',') mod = mod[:col] else: fromlist = [] importer = _importer(scope, mod, fromlist) if fromlist: for name in fromlist: scope[name] = _replacer_from(importer, name) else: dot = mod.find('.') if dot >= 0: basemod = mod[:dot] val = scope.get(basemod) # if base module has already been demandload()ed, # remember to load this submodule into its namespace # when needed. if isinstance(val, _replacer): later = object.__getattribute__(val, 'later') later.append(mod[dot+1:]) continue else: basemod = mod scope[basemod] = _replacer(importer, basemod)