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"""
11from itertools import chain, imap
12from jinja2.nodes import EvalContext, _context_function_types
13from jinja2.utils import Markup, partial, soft_unicode, escape, missing, \
14     concat, internalcode, next, object_type_repr
15from jinja2.exceptions import UndefinedError, TemplateRuntimeError, \
16     TemplateNotFound
17
18
19# these variables are exported to the template runtime
20__all__ = ['LoopContext', 'TemplateReference', 'Macro', 'Markup',
21           'TemplateRuntimeError', 'missing', 'concat', 'escape',
22           'markup_join', 'unicode_join', 'to_string', 'identity',
23           'TemplateNotFound']
24
25#: the name of the function that is used to convert something into
26#: a string.  2to3 will adopt that automatically and the generated
27#: code can take advantage of it.
28to_string = unicode
29
30#: the identity function.  Useful for certain things in the environment
31identity = lambda x: x
32
33
34def markup_join(seq):
35    """Concatenation that escapes if necessary and converts to unicode."""
36    buf = []
37    iterator = imap(soft_unicode, seq)
38    for arg in iterator:
39        buf.append(arg)
40        if hasattr(arg, '__html__'):
41            return Markup(u'').join(chain(buf, iterator))
42    return concat(buf)
43
44
45def unicode_join(seq):
46    """Simple args to unicode conversion and concatenation."""
47    return concat(imap(unicode, seq))
48
49
50def new_context(environment, template_name, blocks, vars=None,
51                shared=None, globals=None, locals=None):
52    """Internal helper to for context creation."""
53    if vars is None:
54        vars = {}
55    if shared:
56        parent = vars
57    else:
58        parent = dict(globals or (), **vars)
59    if locals:
60        # if the parent is shared a copy should be created because
61        # we don't want to modify the dict passed
62        if shared:
63            parent = dict(parent)
64        for key, value in locals.iteritems():
65            if key[:2] == 'l_' and value is not missing:
66                parent[key[2:]] = value
67    return Context(environment, parent, template_name, blocks)
68
69
70class TemplateReference(object):
71    """The `self` in templates."""
72
73    def __init__(self, context):
74        self.__context = context
75
76    def __getitem__(self, name):
77        blocks = self.__context.blocks[name]
78        return BlockReference(name, self.__context, blocks, 0)
79
80    def __repr__(self):
81        return '<%s %r>' % (
82            self.__class__.__name__,
83            self.__context.name
84        )
85
86
87class Context(object):
88    """The template context holds the variables of a template.  It stores the
89    values passed to the template and also the names the template exports.
90    Creating instances is neither supported nor useful as it's created
91    automatically at various stages of the template evaluation and should not
92    be created by hand.
93
94    The context is immutable.  Modifications on :attr:`parent` **must not**
95    happen and modifications on :attr:`vars` are allowed from generated
96    template code only.  Template filters and global functions marked as
97    :func:`contextfunction`\s get the active context passed as first argument
98    and are allowed to access the context read-only.
99
100    The template context supports read only dict operations (`get`,
101    `keys`, `values`, `items`, `iterkeys`, `itervalues`, `iteritems`,
102    `__getitem__`, `__contains__`).  Additionally there is a :meth:`resolve`
103    method that doesn't fail with a `KeyError` but returns an
104    :class:`Undefined` object for missing variables.
105    """
106    __slots__ = ('parent', 'vars', 'environment', 'eval_ctx', 'exported_vars',
107                 'name', 'blocks', '__weakref__')
108
109    def __init__(self, environment, parent, name, blocks):
110        self.parent = parent
111        self.vars = {}
112        self.environment = environment
113        self.eval_ctx = EvalContext(self.environment, name)
114        self.exported_vars = set()
115        self.name = name
116
117        # create the initial mapping of blocks.  Whenever template inheritance
118        # takes place the runtime will update this mapping with the new blocks
119        # from the template.
120        self.blocks = dict((k, [v]) for k, v in blocks.iteritems())
121
122    def super(self, name, current):
123        """Render a parent block."""
124        try:
125            blocks = self.blocks[name]
126            index = blocks.index(current) + 1
127            blocks[index]
128        except LookupError:
129            return self.environment.undefined('there is no parent block '
130                                              'called %r.' % name,
131                                              name='super')
132        return BlockReference(name, self, blocks, index)
133
134    def get(self, key, default=None):
135        """Returns an item from the template context, if it doesn't exist
136        `default` is returned.
137        """
138        try:
139            return self[key]
140        except KeyError:
141            return default
142
143    def resolve(self, key):
144        """Looks up a variable like `__getitem__` or `get` but returns an
145        :class:`Undefined` object with the name of the name looked up.
146        """
147        if key in self.vars:
148            return self.vars[key]
149        if key in self.parent:
150            return self.parent[key]
151        return self.environment.undefined(name=key)
152
153    def get_exported(self):
154        """Get a new dict with the exported variables."""
155        return dict((k, self.vars[k]) for k in self.exported_vars)
156
157    def get_all(self):
158        """Return a copy of the complete context as dict including the
159        exported variables.
160        """
161        return dict(self.parent, **self.vars)
162
163    @internalcode
164    def call(__self, __obj, *args, **kwargs):
165        """Call the callable with the arguments and keyword arguments
166        provided but inject the active context or environment as first
167        argument if the callable is a :func:`contextfunction` or
168        :func:`environmentfunction`.
169        """
170        if __debug__:
171            __traceback_hide__ = True
172        if isinstance(__obj, _context_function_types):
173            if getattr(__obj, 'contextfunction', 0):
174                args = (__self,) + args
175            elif getattr(__obj, 'evalcontextfunction', 0):
176                args = (__self.eval_ctx,) + args
177            elif getattr(__obj, 'environmentfunction', 0):
178                args = (__self.environment,) + args
179        try:
180            return __obj(*args, **kwargs)
181        except StopIteration:
182            return __self.environment.undefined('value was undefined because '
183                                                'a callable raised a '
184                                                'StopIteration exception')
185
186    def derived(self, locals=None):
187        """Internal helper function to create a derived context."""
188        context = new_context(self.environment, self.name, {},
189                              self.parent, True, None, locals)
190        context.vars.update(self.vars)
191        context.eval_ctx = self.eval_ctx
192        context.blocks.update((k, list(v)) for k, v in self.blocks.iteritems())
193        return context
194
195    def _all(meth):
196        proxy = lambda self: getattr(self.get_all(), meth)()
197        proxy.__doc__ = getattr(dict, meth).__doc__
198        proxy.__name__ = meth
199        return proxy
200
201    keys = _all('keys')
202    values = _all('values')
203    items = _all('items')
204
205    # not available on python 3
206    if hasattr(dict, 'iterkeys'):
207        iterkeys = _all('iterkeys')
208        itervalues = _all('itervalues')
209        iteritems = _all('iteritems')
210    del _all
211
212    def __contains__(self, name):
213        return name in self.vars or name in self.parent
214
215    def __getitem__(self, key):
216        """Lookup a variable or raise `KeyError` if the variable is
217        undefined.
218        """
219        item = self.resolve(key)
220        if isinstance(item, Undefined):
221            raise KeyError(key)
222        return item
223
224    def __repr__(self):
225        return '<%s %s of %r>' % (
226            self.__class__.__name__,
227            repr(self.get_all()),
228            self.name
229        )
230
231
232# register the context as mapping if possible
233try:
234    from collections import Mapping
235    Mapping.register(Context)
236except ImportError:
237    pass
238
239
240class BlockReference(object):
241    """One block on a template reference."""
242
243    def __init__(self, name, context, stack, depth):
244        self.name = name
245        self._context = context
246        self._stack = stack
247        self._depth = depth
248
249    @property
250    def super(self):
251        """Super the block."""
252        if self._depth + 1 >= len(self._stack):
253            return self._context.environment. \
254                undefined('there is no parent block called %r.' %
255                          self.name, name='super')
256        return BlockReference(self.name, self._context, self._stack,
257                              self._depth + 1)
258
259    @internalcode
260    def __call__(self):
261        rv = concat(self._stack[self._depth](self._context))
262        if self._context.eval_ctx.autoescape:
263            rv = Markup(rv)
264        return rv
265
266
267class LoopContext(object):
268    """A loop context for dynamic iteration."""
269
270    def __init__(self, iterable, recurse=None):
271        self._iterator = iter(iterable)
272        self._recurse = recurse
273        self.index0 = -1
274
275        # try to get the length of the iterable early.  This must be done
276        # here because there are some broken iterators around where there
277        # __len__ is the number of iterations left (i'm looking at your
278        # listreverseiterator!).
279        try:
280            self._length = len(iterable)
281        except (TypeError, AttributeError):
282            self._length = None
283
284    def cycle(self, *args):
285        """Cycles among the arguments with the current loop index."""
286        if not args:
287            raise TypeError('no items for cycling given')
288        return args[self.index0 % len(args)]
289
290    first = property(lambda x: x.index0 == 0)
291    last = property(lambda x: x.index0 + 1 == x.length)
292    index = property(lambda x: x.index0 + 1)
293    revindex = property(lambda x: x.length - x.index0)
294    revindex0 = property(lambda x: x.length - x.index)
295
296    def __len__(self):
297        return self.length
298
299    def __iter__(self):
300        return LoopContextIterator(self)
301
302    @internalcode
303    def loop(self, iterable):
304        if self._recurse is None:
305            raise TypeError('Tried to call non recursive loop.  Maybe you '
306                            "forgot the 'recursive' modifier.")
307        return self._recurse(iterable, self._recurse)
308
309    # a nifty trick to enhance the error message if someone tried to call
310    # the the loop without or with too many arguments.
311    __call__ = loop
312    del loop
313
314    @property
315    def length(self):
316        if self._length is None:
317            # if was not possible to get the length of the iterator when
318            # the loop context was created (ie: iterating over a generator)
319            # we have to convert the iterable into a sequence and use the
320            # length of that.
321            iterable = tuple(self._iterator)
322            self._iterator = iter(iterable)
323            self._length = len(iterable) + self.index0 + 1
324        return self._length
325
326    def __repr__(self):
327        return '<%s %r/%r>' % (
328            self.__class__.__name__,
329            self.index,
330            self.length
331        )
332
333
334class LoopContextIterator(object):
335    """The iterator for a loop context."""
336    __slots__ = ('context',)
337
338    def __init__(self, context):
339        self.context = context
340
341    def __iter__(self):
342        return self
343
344    def next(self):
345        ctx = self.context
346        ctx.index0 += 1
347        return next(ctx._iterator), ctx
348
349
350class Macro(object):
351    """Wraps a macro function."""
352
353    def __init__(self, environment, func, name, arguments, defaults,
354                 catch_kwargs, catch_varargs, caller):
355        self._environment = environment
356        self._func = func
357        self._argument_count = len(arguments)
358        self.name = name
359        self.arguments = arguments
360        self.defaults = defaults
361        self.catch_kwargs = catch_kwargs
362        self.catch_varargs = catch_varargs
363        self.caller = caller
364
365    @internalcode
366    def __call__(self, *args, **kwargs):
367        # try to consume the positional arguments
368        arguments = list(args[:self._argument_count])
369        off = len(arguments)
370
371        # if the number of arguments consumed is not the number of
372        # arguments expected we start filling in keyword arguments
373        # and defaults.
374        if off != self._argument_count:
375            for idx, name in enumerate(self.arguments[len(arguments):]):
376                try:
377                    value = kwargs.pop(name)
378                except KeyError:
379                    try:
380                        value = self.defaults[idx - self._argument_count + off]
381                    except IndexError:
382                        value = self._environment.undefined(
383                            'parameter %r was not provided' % name, name=name)
384                arguments.append(value)
385
386        # it's important that the order of these arguments does not change
387        # if not also changed in the compiler's `function_scoping` method.
388        # the order is caller, keyword arguments, positional arguments!
389        if self.caller:
390            caller = kwargs.pop('caller', None)
391            if caller is None:
392                caller = self._environment.undefined('No caller defined',
393                                                     name='caller')
394            arguments.append(caller)
395        if self.catch_kwargs:
396            arguments.append(kwargs)
397        elif kwargs:
398            raise TypeError('macro %r takes no keyword argument %r' %
399                            (self.name, next(iter(kwargs))))
400        if self.catch_varargs:
401            arguments.append(args[self._argument_count:])
402        elif len(args) > self._argument_count:
403            raise TypeError('macro %r takes not more than %d argument(s)' %
404                            (self.name, len(self.arguments)))
405        return self._func(*arguments)
406
407    def __repr__(self):
408        return '<%s %s>' % (
409            self.__class__.__name__,
410            self.name is None and 'anonymous' or repr(self.name)
411        )
412
413
414class Undefined(object):
415    """The default undefined type.  This undefined type can be printed and
416    iterated over, but every other access will raise an :exc:`UndefinedError`:
417
418    >>> foo = Undefined(name='foo')
419    >>> str(foo)
420    ''
421    >>> not foo
422    True
423    >>> foo + 42
424    Traceback (most recent call last):
425      ...
426    UndefinedError: 'foo' is undefined
427    """
428    __slots__ = ('_undefined_hint', '_undefined_obj', '_undefined_name',
429                 '_undefined_exception')
430
431    def __init__(self, hint=None, obj=missing, name=None, exc=UndefinedError):
432        self._undefined_hint = hint
433        self._undefined_obj = obj
434        self._undefined_name = name
435        self._undefined_exception = exc
436
437    @internalcode
438    def _fail_with_undefined_error(self, *args, **kwargs):
439        """Regular callback function for undefined objects that raises an
440        `UndefinedError` on call.
441        """
442        if self._undefined_hint is None:
443            if self._undefined_obj is missing:
444                hint = '%r is undefined' % self._undefined_name
445            elif not isinstance(self._undefined_name, basestring):
446                hint = '%s has no element %r' % (
447                    object_type_repr(self._undefined_obj),
448                    self._undefined_name
449                )
450            else:
451                hint = '%r has no attribute %r' % (
452                    object_type_repr(self._undefined_obj),
453                    self._undefined_name
454                )
455        else:
456            hint = self._undefined_hint
457        raise self._undefined_exception(hint)
458
459    @internalcode
460    def __getattr__(self, name):
461        if name[:2] == '__':
462            raise AttributeError(name)
463        return self._fail_with_undefined_error()
464
465    __add__ = __radd__ = __mul__ = __rmul__ = __div__ = __rdiv__ = \
466    __truediv__ = __rtruediv__ = __floordiv__ = __rfloordiv__ = \
467    __mod__ = __rmod__ = __pos__ = __neg__ = __call__ = \
468    __getitem__ = __lt__ = __le__ = __gt__ = __ge__ = __int__ = \
469    __float__ = __complex__ = __pow__ = __rpow__ = \
470        _fail_with_undefined_error
471
472    def __str__(self):
473        return unicode(self).encode('utf-8')
474
475    # unicode goes after __str__ because we configured 2to3 to rename
476    # __unicode__ to __str__.  because the 2to3 tree is not designed to
477    # remove nodes from it, we leave the above __str__ around and let
478    # it override at runtime.
479    def __unicode__(self):
480        return u''
481
482    def __len__(self):
483        return 0
484
485    def __iter__(self):
486        if 0:
487            yield None
488
489    def __nonzero__(self):
490        return False
491
492    def __repr__(self):
493        return 'Undefined'
494
495
496class DebugUndefined(Undefined):
497    """An undefined that returns the debug info when printed.
498
499    >>> foo = DebugUndefined(name='foo')
500    >>> str(foo)
501    '{{ foo }}'
502    >>> not foo
503    True
504    >>> foo + 42
505    Traceback (most recent call last):
506      ...
507    UndefinedError: 'foo' is undefined
508    """
509    __slots__ = ()
510
511    def __unicode__(self):
512        if self._undefined_hint is None:
513            if self._undefined_obj is missing:
514                return u'{{ %s }}' % self._undefined_name
515            return '{{ no such element: %s[%r] }}' % (
516                object_type_repr(self._undefined_obj),
517                self._undefined_name
518            )
519        return u'{{ undefined value printed: %s }}' % self._undefined_hint
520
521
522class StrictUndefined(Undefined):
523    """An undefined that barks on print and iteration as well as boolean
524    tests and all kinds of comparisons.  In other words: you can do nothing
525    with it except checking if it's defined using the `defined` test.
526
527    >>> foo = StrictUndefined(name='foo')
528    >>> str(foo)
529    Traceback (most recent call last):
530      ...
531    UndefinedError: 'foo' is undefined
532    >>> not foo
533    Traceback (most recent call last):
534      ...
535    UndefinedError: 'foo' is undefined
536    >>> foo + 42
537    Traceback (most recent call last):
538      ...
539    UndefinedError: 'foo' is undefined
540    """
541    __slots__ = ()
542    __iter__ = __unicode__ = __str__ = __len__ = __nonzero__ = __eq__ = \
543        __ne__ = __bool__ = Undefined._fail_with_undefined_error
544
545
546# remove remaining slots attributes, after the metaclass did the magic they
547# are unneeded and irritating as they contain wrong data for the subclasses.
548del Undefined.__slots__, DebugUndefined.__slots__, StrictUndefined.__slots__
549