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Diffstat (limited to 'cobbler/Cheetah/NameMapper.py')
| -rw-r--r-- | cobbler/Cheetah/NameMapper.py | 355 |
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diff --git a/cobbler/Cheetah/NameMapper.py b/cobbler/Cheetah/NameMapper.py deleted file mode 100644 index 2d6d953..0000000 --- a/cobbler/Cheetah/NameMapper.py +++ /dev/null @@ -1,355 +0,0 @@ -#!/usr/bin/env python -# $Id: NameMapper.py,v 1.29 2006/01/15 20:27:42 tavis_rudd Exp $ - -"""This module supports Cheetah's optional NameMapper syntax. - -Overview -================================================================================ - -NameMapper provides a simple syntax for accessing Python data structures, -functions, and methods from Cheetah. It's called NameMapper because it 'maps' -simple 'names' in Cheetah templates to possibly more complex syntax in Python. - -Its purpose is to make working with Cheetah easy for non-programmers. -Specifically, non-programmers using Cheetah should NOT need to be taught (a) -what the difference is between an object and a dictionary, (b) what functions -and methods are, and (c) what 'self' is. A further aim (d) is to buffer the -code in Cheetah templates from changes in the implementation of the Python data -structures behind them. - -Consider this scenario: - -You are building a customer information system. The designers with you want to -use information from your system on the client's website --AND-- they want to -understand the display code and so they can maintian it themselves. - -You write a UI class with a 'customers' method that returns a dictionary of all -the customer objects. Each customer object has an 'address' method that returns -the a dictionary with information about the customer's address. The designers -want to be able to access that information. - -Using PSP, the display code for the website would look something like the -following, assuming your servlet subclasses the class you created for managing -customer information: - - <%= self.customer()[ID].address()['city'] %> (42 chars) - -Using Cheetah's NameMapper syntax it could be any of the following: - - $self.customers()[$ID].address()['city'] (39 chars) - --OR-- - $customers()[$ID].address()['city'] - --OR-- - $customers()[$ID].address().city - --OR-- - $customers()[$ID].address.city - --OR-- - $customers()[$ID].address.city - --OR-- - $customers[$ID].address.city (27 chars) - - -Which of these would you prefer to explain to the designers, who have no -programming experience? The last form is 15 characters shorter than the PSP -and, conceptually, is far more accessible. With PHP or ASP, the code would be -even messier than the PSP - -This is a rather extreme example and, of course, you could also just implement -'$getCustomer($ID).city' and obey the Law of Demeter (search Google for more on that). -But good object orientated design isn't the point here. - -Details -================================================================================ -The parenthesized letters below correspond to the aims in the second paragraph. - -DICTIONARY ACCESS (a) ---------------------- - -NameMapper allows access to items in a dictionary using the same dotted notation -used to access object attributes in Python. This aspect of NameMapper is known -as 'Unified Dotted Notation'. - -For example, with Cheetah it is possible to write: - $customers()['kerr'].address() --OR-- $customers().kerr.address() -where the second form is in NameMapper syntax. - -This only works with dictionary keys that are also valid python identifiers: - regex = '[a-zA-Z_][a-zA-Z_0-9]*' - - -AUTOCALLING (b,d) ------------------ - -NameMapper automatically detects functions and methods in Cheetah $vars and calls -them if the parentheses have been left off. - -For example if 'a' is an object, 'b' is a method - $a.b -is equivalent to - $a.b() - -If b returns a dictionary, then following variations are possible - $a.b.c --OR-- $a.b().c --OR-- $a.b()['c'] -where 'c' is a key in the dictionary that a.b() returns. - -Further notes: -* NameMapper autocalls the function or method without any arguments. Thus -autocalling can only be used with functions or methods that either have no -arguments or have default values for all arguments. - -* NameMapper only autocalls functions and methods. Classes and callable object instances -will not be autocalled. - -* Autocalling can be disabled using Cheetah's 'useAutocalling' setting. - -LEAVING OUT 'self' (c,d) ------------------------- - -NameMapper makes it possible to access the attributes of a servlet in Cheetah -without needing to include 'self' in the variable names. See the NAMESPACE -CASCADING section below for details. - -NAMESPACE CASCADING (d) --------------------- -... - -Implementation details -================================================================================ - -* NameMapper's search order is dictionary keys then object attributes - -* NameMapper.NotFound is raised if a value can't be found for a name. - -Performance and the C version -================================================================================ - -Cheetah comes with both a C version and a Python version of NameMapper. The C -version is significantly faster and the exception tracebacks are much easier to -read. It's still slower than standard Python syntax, but you won't notice the -difference in realistic usage scenarios. - -Cheetah uses the optimized C version (_namemapper.c) if it has -been compiled or falls back to the Python version if not. - -Meta-Data -================================================================================ -Authors: Tavis Rudd <tavis@damnsimple.com>, - Chuck Esterbrook <echuck@mindspring.com> -Version: $Revision: 1.29 $ -Start Date: 2001/04/03 -Last Revision Date: $Date: 2006/01/15 20:27:42 $ -""" -from __future__ import generators -__author__ = "Tavis Rudd <tavis@damnsimple.com>," +\ - "\nChuck Esterbrook <echuck@mindspring.com>" -__revision__ = "$Revision: 1.29 $"[11:-2] -import types -from types import StringType, InstanceType, ClassType, TypeType -from pprint import pformat -import inspect - -_INCLUDE_NAMESPACE_REPR_IN_NOTFOUND_EXCEPTIONS = False -_ALLOW_WRAPPING_OF_NOTFOUND_EXCEPTIONS = True -__all__ = ['NotFound', - 'hasKey', - 'valueForKey', - 'valueForName', - 'valueFromSearchList', - 'valueFromFrameOrSearchList', - 'valueFromFrame', - ] - - -## N.B. An attempt is made at the end of this module to import C versions of -## these functions. If _namemapper.c has been compiled succesfully and the -## import goes smoothly, the Python versions defined here will be replaced with -## the C versions. - -class NotFound(LookupError): - pass - -def _raiseNotFoundException(key, namespace): - excString = "cannot find '%s'"%key - if _INCLUDE_NAMESPACE_REPR_IN_NOTFOUND_EXCEPTIONS: - excString += ' in the namespace %s'%pformat(namespace) - raise NotFound(excString) - -def _wrapNotFoundException(exc, fullName, namespace): - if not _ALLOW_WRAPPING_OF_NOTFOUND_EXCEPTIONS: - raise - else: - excStr = exc.args[0] - if excStr.find('while searching')==-1: # only wrap once! - excStr +=" while searching for '%s'"%fullName - if _INCLUDE_NAMESPACE_REPR_IN_NOTFOUND_EXCEPTIONS: - excString += ' in the namespace %s'%pformat(namespace) - exc.args = (excStr,) - raise - -def hasKey(obj, key): - """Determine if 'obj' has 'key' """ - if hasattr(obj,'has_key') and obj.has_key(key): - return True - elif hasattr(obj, key): - return True - else: - return False - -def valueForKey(obj, key): - if hasattr(obj, 'has_key') and obj.has_key(key): - return obj[key] - elif hasattr(obj, key): - return getattr(obj, key) - else: - _raiseNotFoundException(key, obj) - -def _valueForName(obj, name, executeCallables=False): - nameChunks=name.split('.') - for i in range(len(nameChunks)): - key = nameChunks[i] - if hasattr(obj, 'has_key') and obj.has_key(key): - nextObj = obj[key] - elif hasattr(obj, key): - nextObj = getattr(obj, key) - else: - _raiseNotFoundException(key, obj) - - if (executeCallables and callable(nextObj) - and (type(nextObj) not in (InstanceType, ClassType))): - obj = nextObj() - else: - obj = nextObj - return obj - -def valueForName(obj, name, executeCallables=False): - try: - return _valueForName(obj, name, executeCallables) - except NotFound, e: - _wrapNotFoundException(e, fullName=name, namespace=obj) - -def valueFromSearchList(searchList, name, executeCallables=False): - key = name.split('.')[0] - for namespace in searchList: - if hasKey(namespace, key): - return _valueForName(namespace, name, - executeCallables=executeCallables) - _raiseNotFoundException(key, searchList) - -def _namespaces(callerFrame, searchList=None): - yield callerFrame.f_locals - if searchList: - for namespace in searchList: - yield namespace - yield callerFrame.f_globals - yield __builtins__ - -def valueFromFrameOrSearchList(searchList, name, executeCallables=False, - frame=None): - def __valueForName(): - try: - return _valueForName(namespace, name, executeCallables=executeCallables) - except NotFound, e: - _wrapNotFoundException(e, fullName=name, namespace=searchList) - try: - if not frame: - frame = inspect.stack()[1][0] - key = name.split('.')[0] - for namespace in _namespaces(frame, searchList): - if hasKey(namespace, key): return __valueForName() - _raiseNotFoundException(key, searchList) - finally: - del frame - -def valueFromFrame(name, executeCallables=False, frame=None): - # @@TR consider implementing the C version the same way - # at the moment it provides a seperate but mirror implementation - # to valueFromFrameOrSearchList - try: - if not frame: - frame = inspect.stack()[1][0] - return valueFromFrameOrSearchList(searchList=None, - name=name, - executeCallables=executeCallables, - frame=frame) - finally: - del frame - -def hasName(obj, name): - #Not in the C version - """Determine if 'obj' has the 'name' """ - key = name.split('.')[0] - if not hasKey(obj, key): - return False - try: - valueForName(obj, name) - return True - except NotFound: - return False -try: - from _namemapper import NotFound, valueForKey, valueForName, \ - valueFromSearchList, valueFromFrameOrSearchList, valueFromFrame - # it is possible with Jython or Windows, for example, that _namemapper.c hasn't been compiled - C_VERSION = True -except: - C_VERSION = False - -################################################## -## CLASSES - -class Mixin: - """@@ document me""" - def valueForName(self, name): - return valueForName(self, name) - - def valueForKey(self, key): - return valueForKey(self, key) - -################################################## -## if run from the command line ## - -def example(): - class A(Mixin): - classVar = 'classVar val' - def method(self,arg='method 1 default arg'): - return arg - - def method2(self, arg='meth 2 default arg'): - return {'item1':arg} - - def method3(self, arg='meth 3 default'): - return arg - - class B(A): - classBvar = 'classBvar val' - - a = A() - a.one = 'valueForOne' - def function(whichOne='default'): - values = { - 'default': 'default output', - 'one': 'output option one', - 'two': 'output option two' - } - return values[whichOne] - - a.dic = { - 'func': function, - 'method': a.method3, - 'item': 'itemval', - 'subDict': {'nestedMethod':a.method3} - } - b = 'this is local b' - - print valueForKey(a.dic,'subDict') - print valueForName(a, 'dic.item') - print valueForName(vars(), 'b') - print valueForName(__builtins__, 'dir')() - print valueForName(vars(), 'a.classVar') - print valueForName(vars(), 'a.dic.func', executeCallables=True) - print valueForName(vars(), 'a.method2.item1', executeCallables=True) - -if __name__ == '__main__': - example() - - - |