diff options
Diffstat (limited to 'jinja2/runtime.py')
| -rw-r--r-- | jinja2/runtime.py | 251 |
1 files changed, 157 insertions, 94 deletions
diff --git a/jinja2/runtime.py b/jinja2/runtime.py index ff12ded..135ff27 100644 --- a/jinja2/runtime.py +++ b/jinja2/runtime.py @@ -343,134 +343,197 @@ class BlockReference(object): return rv -class LoopContextBase(object): - """A loop context for dynamic iteration.""" +@implements_iterator +class LoopContext: + """A wrapper iterable for dynamic ``for`` loops, with information + about the loop and iteration. + """ + + #: Current iteration of the loop, starting at 0. + index0 = -1 - _before = _first_iteration - _current = _first_iteration - _after = _last_iteration _length = None + _after = missing + _current = missing + _before = missing + _last_changed_value = missing - def __init__(self, undefined, recurse=None, depth0=0): + def __init__(self, iterable, undefined, recurse=None, depth0=0): + """ + :param iterable: Iterable to wrap. + :param undefined: :class:`Undefined` class to use for next and + previous items. + :param recurse: The function to render the loop body when the + loop is marked recursive. + :param depth0: Incremented when looping recursively. + """ + self._iterable = iterable + self._iterator = self._to_iterator(iterable) self._undefined = undefined self._recurse = recurse - self.index0 = -1 + #: How many levels deep a recursive loop currently is, starting at 0. self.depth0 = depth0 - self._last_checked_value = missing - def cycle(self, *args): - """Cycles among the arguments with the current loop index.""" - if not args: - raise TypeError('no items for cycling given') - return args[self.index0 % len(args)] + @staticmethod + def _to_iterator(iterable): + return iter(iterable) - def changed(self, *value): - """Checks whether the value has changed since the last call.""" - if self._last_checked_value != value: - self._last_checked_value = value - return True - return False + @property + def length(self): + """Length of the iterable. - first = property(lambda x: x.index0 == 0) - last = property(lambda x: x._after is _last_iteration) - index = property(lambda x: x.index0 + 1) - revindex = property(lambda x: x.length - x.index0) - revindex0 = property(lambda x: x.length - x.index) - depth = property(lambda x: x.depth0 + 1) + If the iterable is a generator or otherwise does not have a + size, it is eagerly evaluated to get a size. + """ + if self._length is not None: + return self._length - @property - def previtem(self): - if self._before is _first_iteration: - return self._undefined('there is no previous item') - return self._before + try: + self._length = len(self._iterable) + except TypeError: + iterable = list(self._iterator) + self._iterator = self._to_iterator(iterable) + self._length = len(iterable) + self.index + (self._after is not missing) - @property - def nextitem(self): - if self._after is _last_iteration: - return self._undefined('there is no next item') - return self._after + return self._length def __len__(self): return self.length - @internalcode - def loop(self, iterable): - if self._recurse is None: - raise TypeError('Tried to call non recursive loop. Maybe you ' - "forgot the 'recursive' modifier.") - return self._recurse(iterable, self._recurse, self.depth0 + 1) + @property + def depth(self): + """How many levels deep a recursive loop currently is, starting at 1.""" + return self.depth0 + 1 - # a nifty trick to enhance the error message if someone tried to call - # the loop without or with too many arguments. - __call__ = loop - del loop + @property + def index(self): + """Current iteration of the loop, starting at 1.""" + return self.index0 + 1 - def __repr__(self): - return '<%s %r/%r>' % ( - self.__class__.__name__, - self.index, - self.length - ) + @property + def revindex0(self): + """Number of iterations from the end of the loop, ending at 0. + Requires calculating :attr:`length`. + """ + return self.length - self.index -class LoopContext(LoopContextBase): + @property + def revindex(self): + """Number of iterations from the end of the loop, ending at 1. - def __init__(self, iterable, undefined, recurse=None, depth0=0): - LoopContextBase.__init__(self, undefined, recurse, depth0) - self._iterator = iter(iterable) - self._iterations_done_count = 0 - self._length = None - self._after = self._safe_next() + Requires calculating :attr:`length`. + """ + return self.length - self.index0 @property - def length(self): + def first(self): + """Whether this is the first iteration of the loop.""" + return self.index0 == 0 + + def _peek_next(self): + """Return the next element in the iterable, or :data:`missing` + if the iterable is exhausted. Only peeks one item ahead, caching + the result in :attr:`_last` for use in subsequent checks. The + cache is reset when :meth:`__next__` is called. + """ + if self._after is not missing: + return self._after + + self._after = next(self._iterator, missing) + return self._after + + @property + def last(self): + """Whether this is the last iteration of the loop. + + Causes the iterable to advance early. See + :func:`itertools.groupby` for issues this can cause. + The :func:`groupby` filter avoids that issue. """ - Getting length of an iterator is a costly operation which requires extra memory - and traversing in linear time. So make it an on demand param that iterates from - the point onwards of the iterator and accounts for iterated elements. + return self._peek_next() is missing + + @property + def previtem(self): + """The item in the previous iteration. Undefined during the + first iteration. """ - if self._length is None: - # if was not possible to get the length of the iterator when - # the loop context was created (ie: iterating over a generator) - # we have to convert the iterable into a sequence and use the - # length of that + the number of iterations so far. - iterable = tuple(self._iterator) - self._iterator = iter(iterable) - self._length = len(iterable) + self._iterations_done_count - return self._length + if self.first: + return self._undefined("there is no previous item") - def __iter__(self): - return LoopContextIterator(self) + return self._before - def _safe_next(self): - try: - tmp = next(self._iterator) - self._iterations_done_count += 1 - return tmp - except StopIteration: - return _last_iteration + @property + def nextitem(self): + """The item in the next iteration. Undefined during the last + iteration. + Causes the iterable to advance early. See + :func:`itertools.groupby` for issues this can cause. + The :func:`groupby` filter avoids that issue. + """ + rv = self._peek_next() -@implements_iterator -class LoopContextIterator(object): - """The iterator for a loop context.""" - __slots__ = ('context',) + if rv is missing: + return self._undefined("there is no next item") - def __init__(self, context): - self.context = context + return rv + + def cycle(self, *args): + """Return a value from the given args, cycling through based on + the current :attr:`index0`. + + :param args: One or more values to cycle through. + """ + if not args: + raise TypeError("no items for cycling given") + + return args[self.index0 % len(args)] + + def changed(self, *value): + """Return ``True`` if previously called with a different value + (including when called for the first time). + + :param value: One or more values to compare to the last call. + """ + if self._last_changed_value != value: + self._last_changed_value = value + return True + + return False def __iter__(self): return self + @internalcode def __next__(self): - ctx = self.context - ctx.index0 += 1 - if ctx._after is _last_iteration: - raise StopIteration() - ctx._before = ctx._current - ctx._current = ctx._after - ctx._after = ctx._safe_next() - return ctx._current, ctx + if self._after is not missing: + rv = self._after + self._after = missing + else: + rv = next(self._iterator) + + self.index0 += 1 + self._before = self._current + self._current = rv + return rv, self + + def __call__(self, iterable): + """When iterating over nested data, render the body of the loop + recursively with the given inner iterable data. + + The loop must have the ``recursive`` marker for this to work. + """ + if self._recurse is None: + raise TypeError( + "The loop must have the 'recursive' marker to be" + " called recursively." + ) + + return self._recurse(iterable, self._recurse, depth=self.depth) + + def __repr__(self): + return "<%s %d/%d>" % (self.__class__.__name__, self.index, self.length) class Macro(object): |