third_party/jinja2/runtime.py

   1 # -*- coding: utf-8 -*-
   2 """
   3     jinja2.runtime
   4     ~~~~~~~~~~~~~~
   5
   6     Runtime helpers.
   7
   8     :copyright: (c) 2010 by the Jinja Team.
   9     :license: BSD.
  10 """
  11 from itertools import chain
  12 from jinja2.nodes import EvalContext, _context_function_types
  13 from jinja2.utils import Markup, soft_unicode, escape, missing, concat, \
  14      internalcode, object_type_repr
  15 from jinja2.exceptions import UndefinedError, TemplateRuntimeError, \
  16      TemplateNotFound
  17 from jinja2._compat import next, imap, text_type, iteritems, \
  18      implements_iterator, implements_to_string, string_types, PY2
  19
  20
  21 # these variables are exported to the template runtime
  22 __all__ = ['LoopContext', 'TemplateReference', 'Macro', 'Markup',
  23            'TemplateRuntimeError', 'missing', 'concat', 'escape',
  24            'markup_join', 'unicode_join', 'to_string', 'identity',
  25            'TemplateNotFound']
  26
  27 #: the name of the function that is used to convert something into
  28 #: a string.  We can just use the text type here.
  29 to_string = text_type
  30
  31 #: the identity function.  Useful for certain things in the environment
  32 identity = lambda x: x
  33
  34 _last_iteration = object()
  35
  36
  37 def markup_join(seq):
  38     """Concatenation that escapes if necessary and converts to unicode."""
  39     buf = []
  40     iterator = imap(soft_unicode, seq)
  41     for arg in iterator:
  42         buf.append(arg)
  43         if hasattr(arg, '__html__'):
  44             return Markup(u'').join(chain(buf, iterator))
  45     return concat(buf)
  46
  47
  48 def unicode_join(seq):
  49     """Simple args to unicode conversion and concatenation."""
  50     return concat(imap(text_type, seq))
  51
  52
  53 def new_context(environment, template_name, blocks, vars=None,
  54                 shared=None, globals=None, locals=None):
  55     """Internal helper to for context creation."""
  56     if vars is None:
  57         vars = {}
  58     if shared:
  59         parent = vars
  60     else:
  61         parent = dict(globals or (), **vars)
  62     if locals:
  63         # if the parent is shared a copy should be created because
  64         # we don't want to modify the dict passed
  65         if shared:
  66             parent = dict(parent)
  67         for key, value in iteritems(locals):
  68             if key[:2] == 'l_' and value is not missing:
  69                 parent[key[2:]] = value
  70     return Context(environment, parent, template_name, blocks)
  71
  72
  73 class TemplateReference(object):
  74     """The `self` in templates."""
  75
  76     def __init__(self, context):
  77         self.__context = context
  78
  79     def __getitem__(self, name):
  80         blocks = self.__context.blocks[name]
  81         return BlockReference(name, self.__context, blocks, 0)
  82
  83     def __repr__(self):
  84         return '<%s %r>' % (
  85             self.__class__.__name__,
  86             self.__context.name
  87         )
  88
  89
  90 class Context(object):
  91     """The template context holds the variables of a template.  It stores the
  92     values passed to the template and also the names the template exports.
  93     Creating instances is neither supported nor useful as it's created
  94     automatically at various stages of the template evaluation and should not
  95     be created by hand.
  96
  97     The context is immutable.  Modifications on :attr:`parent` **must not**
  98     happen and modifications on :attr:`vars` are allowed from generated
  99     template code only.  Template filters and global functions marked as
 100     :func:`contextfunction`\s get the active context passed as first argument
 101     and are allowed to access the context read-only.
 102
 103     The template context supports read only dict operations (`get`,
 104     `keys`, `values`, `items`, `iterkeys`, `itervalues`, `iteritems`,
 105     `__getitem__`, `__contains__`).  Additionally there is a :meth:`resolve`
 106     method that doesn't fail with a `KeyError` but returns an
 107     :class:`Undefined` object for missing variables.
 108     """
 109     __slots__ = ('parent', 'vars', 'environment', 'eval_ctx', 'exported_vars',
 110                  'name', 'blocks', '__weakref__')
 111
 112     def __init__(self, environment, parent, name, blocks):
 113         self.parent = parent
 114         self.vars = {}
 115         self.environment = environment
 116         self.eval_ctx = EvalContext(self.environment, name)
 117         self.exported_vars = set()
 118         self.name = name
 119
 120         # create the initial mapping of blocks.  Whenever template inheritance
 121         # takes place the runtime will update this mapping with the new blocks
 122         # from the template.
 123         self.blocks = dict((k, [v]) for k, v in iteritems(blocks))
 124
 125     def super(self, name, current):
 126         """Render a parent block."""
 127         try:
 128             blocks = self.blocks[name]
 129             index = blocks.index(current) + 1
 130             blocks[index]
 131         except LookupError:
 132             return self.environment.undefined('there is no parent block '
 133                                               'called %r.' % name,
 134                                               name='super')
 135         return BlockReference(name, self, blocks, index)
 136
 137     def get(self, key, default=None):
 138         """Returns an item from the template context, if it doesn't exist
 139         `default` is returned.
 140         """
 141         try:
 142             return self[key]
 143         except KeyError:
 144             return default
 145
 146     def resolve(self, key):
 147         """Looks up a variable like `__getitem__` or `get` but returns an
 148         :class:`Undefined` object with the name of the name looked up.
 149         """
 150         if key in self.vars:
 151             return self.vars[key]
 152         if key in self.parent:
 153             return self.parent[key]
 154         return self.environment.undefined(name=key)
 155
 156     def get_exported(self):
 157         """Get a new dict with the exported variables."""
 158         return dict((k, self.vars[k]) for k in self.exported_vars)
 159
 160     def get_all(self):
 161         """Return a copy of the complete context as dict including the
 162         exported variables.
 163         """
 164         return dict(self.parent, **self.vars)
 165
 166     @internalcode
 167     def call(__self, __obj, *args, **kwargs):
 168         """Call the callable with the arguments and keyword arguments
 169         provided but inject the active context or environment as first
 170         argument if the callable is a :func:`contextfunction` or
 171         :func:`environmentfunction`.
 172         """
 173         if __debug__:
 174             __traceback_hide__ = True
 175
 176         # Allow callable classes to take a context
 177         fn = __obj.__call__
 178         for fn_type in ('contextfunction',
 179                         'evalcontextfunction',
 180                         'environmentfunction'):
 181             if hasattr(fn, fn_type):
 182                 __obj = fn
 183                 break
 184
 185         if isinstance(__obj, _context_function_types):
 186             if getattr(__obj, 'contextfunction', 0):
 187                 args = (__self,) + args
 188             elif getattr(__obj, 'evalcontextfunction', 0):
 189                 args = (__self.eval_ctx,) + args
 190             elif getattr(__obj, 'environmentfunction', 0):
 191                 args = (__self.environment,) + args
 192         try:
 193             return __obj(*args, **kwargs)
 194         except StopIteration:
 195             return __self.environment.undefined('value was undefined because '
 196                                                 'a callable raised a '
 197                                                 'StopIteration exception')
 198
 199     def derived(self, locals=None):
 200         """Internal helper function to create a derived context."""
 201         context = new_context(self.environment, self.name, {},
 202                               self.parent, True, None, locals)
 203         context.vars.update(self.vars)
 204         context.eval_ctx = self.eval_ctx
 205         context.blocks.update((k, list(v)) for k, v in iteritems(self.blocks))
 206         return context
 207
 208     def _all(meth):
 209         proxy = lambda self: getattr(self.get_all(), meth)()
 210         proxy.__doc__ = getattr(dict, meth).__doc__
 211         proxy.__name__ = meth
 212         return proxy
 213
 214     keys = _all('keys')
 215     values = _all('values')
 216     items = _all('items')
 217
 218     # not available on python 3
 219     if PY2:
 220         iterkeys = _all('iterkeys')
 221         itervalues = _all('itervalues')
 222         iteritems = _all('iteritems')
 223     del _all
 224
 225     def __contains__(self, name):
 226         return name in self.vars or name in self.parent
 227
 228     def __getitem__(self, key):
 229         """Lookup a variable or raise `KeyError` if the variable is
 230         undefined.
 231         """
 232         item = self.resolve(key)
 233         if isinstance(item, Undefined):
 234             raise KeyError(key)
 235         return item
 236
 237     def __repr__(self):
 238         return '<%s %s of %r>' % (
 239             self.__class__.__name__,
 240             repr(self.get_all()),
 241             self.name
 242         )
 243
 244
 245 # register the context as mapping if possible
 246 try:
 247     from collections import Mapping
 248     Mapping.register(Context)
 249 except ImportError:
 250     pass
 251
 252
 253 class BlockReference(object):
 254     """One block on a template reference."""
 255
 256     def __init__(self, name, context, stack, depth):
 257         self.name = name
 258         self._context = context
 259         self._stack = stack
 260         self._depth = depth
 261
 262     @property
 263     def super(self):
 264         """Super the block."""
 265         if self._depth + 1 >= len(self._stack):
 266             return self._context.environment. \
 267                 undefined('there is no parent block called %r.' %
 268                           self.name, name='super')
 269         return BlockReference(self.name, self._context, self._stack,
 270                               self._depth + 1)
 271
 272     @internalcode
 273     def __call__(self):
 274         rv = concat(self._stack[self._depth](self._context))
 275         if self._context.eval_ctx.autoescape:
 276             rv = Markup(rv)
 277         return rv
 278
 279
 280 class LoopContext(object):
 281     """A loop context for dynamic iteration."""
 282
 283     def __init__(self, iterable, recurse=None, depth0=0):
 284         self._iterator = iter(iterable)
 285         self._recurse = recurse
 286         self._after = self._safe_next()
 287         self.index0 = -1
 288         self.depth0 = depth0
 289
 290         # try to get the length of the iterable early.  This must be done
 291         # here because there are some broken iterators around where there
 292         # __len__ is the number of iterations left (i'm looking at your
 293         # listreverseiterator!).
 294         try:
 295             self._length = len(iterable)
 296         except (TypeError, AttributeError):
 297             self._length = None
 298
 299     def cycle(self, *args):
 300         """Cycles among the arguments with the current loop index."""
 301         if not args:
 302             raise TypeError('no items for cycling given')
 303         return args[self.index0 % len(args)]
 304
 305     first = property(lambda x: x.index0 == 0)
 306     last = property(lambda x: x._after is _last_iteration)
 307     index = property(lambda x: x.index0 + 1)
 308     revindex = property(lambda x: x.length - x.index0)
 309     revindex0 = property(lambda x: x.length - x.index)
 310     depth = property(lambda x: x.depth0 + 1)
 311
 312     def __len__(self):
 313         return self.length
 314
 315     def __iter__(self):
 316         return LoopContextIterator(self)
 317
 318     def _safe_next(self):
 319         try:
 320             return next(self._iterator)
 321         except StopIteration:
 322             return _last_iteration
 323
 324     @internalcode
 325     def loop(self, iterable):
 326         if self._recurse is None:
 327             raise TypeError('Tried to call non recursive loop.  Maybe you '
 328                             "forgot the 'recursive' modifier.")
 329         return self._recurse(iterable, self._recurse, self.depth0 + 1)
 330
 331     # a nifty trick to enhance the error message if someone tried to call
 332     # the the loop without or with too many arguments.
 333     __call__ = loop
 334     del loop
 335
 336     @property
 337     def length(self):
 338         if self._length is None:
 339             # if was not possible to get the length of the iterator when
 340             # the loop context was created (ie: iterating over a generator)
 341             # we have to convert the iterable into a sequence and use the
 342             # length of that.
 343             iterable = tuple(self._iterator)
 344             self._iterator = iter(iterable)
 345             self._length = len(iterable) + self.index0 + 1
 346         return self._length
 347
 348     def __repr__(self):
 349         return '<%s %r/%r>' % (
 350             self.__class__.__name__,
 351             self.index,
 352             self.length
 353         )
 354
 355
 356 @implements_iterator
 357 class LoopContextIterator(object):
 358     """The iterator for a loop context."""
 359     __slots__ = ('context',)
 360
 361     def __init__(self, context):
 362         self.context = context
 363
 364     def __iter__(self):
 365         return self
 366
 367     def __next__(self):
 368         ctx = self.context
 369         ctx.index0 += 1
 370         if ctx._after is _last_iteration:
 371             raise StopIteration()
 372         next_elem = ctx._after
 373         ctx._after = ctx._safe_next()
 374         return next_elem, ctx
 375
 376
 377 class Macro(object):
 378     """Wraps a macro function."""
 379
 380     def __init__(self, environment, func, name, arguments, defaults,
 381                  catch_kwargs, catch_varargs, caller):
 382         self._environment = environment
 383         self._func = func
 384         self._argument_count = len(arguments)
 385         self.name = name
 386         self.arguments = arguments
 387         self.defaults = defaults
 388         self.catch_kwargs = catch_kwargs
 389         self.catch_varargs = catch_varargs
 390         self.caller = caller
 391
 392     @internalcode
 393     def __call__(self, *args, **kwargs):
 394         # try to consume the positional arguments
 395         arguments = list(args[:self._argument_count])
 396         off = len(arguments)
 397
 398         # if the number of arguments consumed is not the number of
 399         # arguments expected we start filling in keyword arguments
 400         # and defaults.
 401         if off != self._argument_count:
 402             for idx, name in enumerate(self.arguments[len(arguments):]):
 403                 try:
 404                     value = kwargs.pop(name)
 405                 except KeyError:
 406                     try:
 407                         value = self.defaults[idx - self._argument_count + off]
 408                     except IndexError:
 409                         value = self._environment.undefined(
 410                             'parameter %r was not provided' % name, name=name)
 411                 arguments.append(value)
 412
 413         # it's important that the order of these arguments does not change
 414         # if not also changed in the compiler's `function_scoping` method.
 415         # the order is caller, keyword arguments, positional arguments!
 416         if self.caller:
 417             caller = kwargs.pop('caller', None)
 418             if caller is None:
 419                 caller = self._environment.undefined('No caller defined',
 420                                                      name='caller')
 421             arguments.append(caller)
 422         if self.catch_kwargs:
 423             arguments.append(kwargs)
 424         elif kwargs:
 425             raise TypeError('macro %r takes no keyword argument %r' %
 426                             (self.name, next(iter(kwargs))))
 427         if self.catch_varargs:
 428             arguments.append(args[self._argument_count:])
 429         elif len(args) > self._argument_count:
 430             raise TypeError('macro %r takes not more than %d argument(s)' %
 431                             (self.name, len(self.arguments)))
 432         return self._func(*arguments)
 433
 434     def __repr__(self):
 435         return '<%s %s>' % (
 436             self.__class__.__name__,
 437             self.name is None and 'anonymous' or repr(self.name)
 438         )
 439
 440
 441 @implements_to_string
 442 class Undefined(object):
 443     """The default undefined type.  This undefined type can be printed and
 444     iterated over, but every other access will raise an :exc:`UndefinedError`:
 445
 446     >>> foo = Undefined(name='foo')
 447     >>> str(foo)
 448     ''
 449     >>> not foo
 450     True
 451     >>> foo + 42
 452     Traceback (most recent call last):
 453       ...
 454     UndefinedError: 'foo' is undefined
 455     """
 456     __slots__ = ('_undefined_hint', '_undefined_obj', '_undefined_name',
 457                  '_undefined_exception')
 458
 459     def __init__(self, hint=None, obj=missing, name=None, exc=UndefinedError):
 460         self._undefined_hint = hint
 461         self._undefined_obj = obj
 462         self._undefined_name = name
 463         self._undefined_exception = exc
 464
 465     @internalcode
 466     def _fail_with_undefined_error(self, *args, **kwargs):
 467         """Regular callback function for undefined objects that raises an
 468         `UndefinedError` on call.
 469         """
 470         if self._undefined_hint is None:
 471             if self._undefined_obj is missing:
 472                 hint = '%r is undefined' % self._undefined_name
 473             elif not isinstance(self._undefined_name, string_types):
 474                 hint = '%s has no element %r' % (
 475                     object_type_repr(self._undefined_obj),
 476                     self._undefined_name
 477                 )
 478             else:
 479                 hint = '%r has no attribute %r' % (
 480                     object_type_repr(self._undefined_obj),
 481                     self._undefined_name
 482                 )
 483         else:
 484             hint = self._undefined_hint
 485         raise self._undefined_exception(hint)
 486
 487     @internalcode
 488     def __getattr__(self, name):
 489         if name[:2] == '__':
 490             raise AttributeError(name)
 491         return self._fail_with_undefined_error()
 492
 493     __add__ = __radd__ = __mul__ = __rmul__ = __div__ = __rdiv__ = \
 494     __truediv__ = __rtruediv__ = __floordiv__ = __rfloordiv__ = \
 495     __mod__ = __rmod__ = __pos__ = __neg__ = __call__ = \
 496     __getitem__ = __lt__ = __le__ = __gt__ = __ge__ = __int__ = \
 497     __float__ = __complex__ = __pow__ = __rpow__ = \
 498         _fail_with_undefined_error
 499
 500     def __eq__(self, other):
 501         return type(self) is type(other)
 502
 503     def __ne__(self, other):
 504         return not self.__eq__(other)
 505
 506     def __hash__(self):
 507         return id(type(self))
 508
 509     def __str__(self):
 510         return u''
 511
 512     def __len__(self):
 513         return 0
 514
 515     def __iter__(self):
 516         if 0:
 517             yield None
 518
 519     def __nonzero__(self):
 520         return False
 521
 522     def __repr__(self):
 523         return 'Undefined'
 524
 525
 526 @implements_to_string
 527 class DebugUndefined(Undefined):
 528     """An undefined that returns the debug info when printed.
 529
 530     >>> foo = DebugUndefined(name='foo')
 531     >>> str(foo)
 532     '{{ foo }}'
 533     >>> not foo
 534     True
 535     >>> foo + 42
 536     Traceback (most recent call last):
 537       ...
 538     UndefinedError: 'foo' is undefined
 539     """
 540     __slots__ = ()
 541
 542     def __str__(self):
 543         if self._undefined_hint is None:
 544             if self._undefined_obj is missing:
 545                 return u'{{ %s }}' % self._undefined_name
 546             return '{{ no such element: %s[%r] }}' % (
 547                 object_type_repr(self._undefined_obj),
 548                 self._undefined_name
 549             )
 550         return u'{{ undefined value printed: %s }}' % self._undefined_hint
 551
 552
 553 @implements_to_string
 554 class StrictUndefined(Undefined):
 555     """An undefined that barks on print and iteration as well as boolean
 556     tests and all kinds of comparisons.  In other words: you can do nothing
 557     with it except checking if it's defined using the `defined` test.
 558
 559     >>> foo = StrictUndefined(name='foo')
 560     >>> str(foo)
 561     Traceback (most recent call last):
 562       ...
 563     UndefinedError: 'foo' is undefined
 564     >>> not foo
 565     Traceback (most recent call last):
 566       ...
 567     UndefinedError: 'foo' is undefined
 568     >>> foo + 42
 569     Traceback (most recent call last):
 570       ...
 571     UndefinedError: 'foo' is undefined
 572     """
 573     __slots__ = ()
 574     __iter__ = __str__ = __len__ = __nonzero__ = __eq__ = \
 575         __ne__ = __bool__ = __hash__ = \
 576         Undefined._fail_with_undefined_error
 577
 578
 579 # remove remaining slots attributes, after the metaclass did the magic they
 580 # are unneeded and irritating as they contain wrong data for the subclasses.
 581 del Undefined.__slots__, DebugUndefined.__slots__, StrictUndefined.__slots__