def test_series(self):
assert parse_series('1n+3') == (1, 3)
assert parse_series('n-5') == (1, -5)
assert parse_series('odd') == (2, 1)
assert parse_series('even') == (2, 0)
assert parse_series('3n') == (3, 0)
assert parse_series('n') == (1, 0)
assert parse_series('+n') == (1, 0)
assert parse_series('-n') == (-1, 0)
assert parse_series('5') == (0, 5)
self.assertRaises(ValueError, parse_series, 'foo')
self.assertRaises(ValueError, parse_series, 'n+')
def xpath_nth_child_function(self, xpath, function, last=False,
add_name_test=True):
try:
a, b = parse_series(function.arguments)
except ValueError:
raise ExpressionError("Invalid series: '%r'" % function.arguments)
if add_name_test:
xpath.add_name_test()
xpath.add_star_prefix()
if a == 0:
if last:
b = 'last() - %s' % b
return xpath.add_condition('position() = %s' % b)
if last:
# FIXME: I'm not sure if this is right
a = -a
b = -b
if b > 0:
b_neg = str(-b)
else:
b_neg = '+%s' % (-b)
if a != 1:
expr = ['(position() %s) mod %s = 0' % (b_neg, a)]
else:
expr = []
if b >= 0:
expr.append('position() >= %s' % b)
elif b < 0 and last:
expr.append('position() < (last() %s)' % b)
expr = ' and '.join(expr)
if expr:
xpath.add_condition(expr)
return xpath
def xpath_nth_child_function(self, xpath, function, last=False,
add_name_test=True):
try:
a, b = parse_series(function.arguments)
except ValueError:
raise ExpressionError("Invalid series: '%r'" % function.arguments)
if add_name_test:
xpath.add_name_test()
xpath.add_star_prefix()
if a == 0:
if last:
b = 'last() - %s' % b
return xpath.add_condition('position() = %s' % b)
if last:
# FIXME: I'm not sure if this is right
a = -a
b = -b
if b > 0:
b_neg = str(-b)
else:
b_neg = '+%s' % (-b)
if a != 1:
expr = ['(position() %s) mod %s = 0' % (b_neg, a)]
else:
expr = []
if b >= 0:
expr.append('position() >= %s' % b)
elif b < 0 and last:
expr.append('position() < (last() %s)' % b)
expr = ' and '.join(expr)
if expr:
xpath.add_condition(expr)
return xpath
def series(css):
selector, = parse(':nth-child(%s)' % css)
args = selector.parsed_tree.arguments
try:
return parse_series(args)
except ValueError:
return None
def series(css):
selector, = parse(':nth-child(%s)' % css)
args = selector.parsed_tree.arguments
try:
return parse_series(args)
except ValueError:
return None
def xpath_nth_child_function(self, xpath, function, last=False,
add_name_test=True):
a, b = parse_series(function.arguments)
if not a and not b and not last:
# a=0 means nothing is returned...
return xpath.add_condition('false() and position() = 0')
if add_name_test:
xpath.add_name_test()
xpath.add_star_prefix()
if a == 0:
if last:
b = 'last() - %s' % b
return xpath.add_condition('position() = %s' % b)
if last:
# FIXME: I'm not sure if this is right
a = -a
b = -b
if b > 0:
b_neg = str(-b)
else:
b_neg = '+%s' % (-b)
if a != 1:
expr = ['(position() %s) mod %s = 0' % (b_neg, a)]
else:
expr = []
if b >= 0:
expr.append('position() >= %s' % b)
elif b < 0 and last:
expr.append('position() < (last() %s)' % b)
expr = ' and '.join(expr)
if expr:
xpath.add_condition(expr)
return xpath
def test_series(self):
assert parse_series('1n+3') == (1, 3)
assert parse_series('n-5') == (1, -5)
assert parse_series('odd') == (2, 1)
assert parse_series('even') == (2, 0)
assert parse_series('3n') == (3, 0)
assert parse_series('n') == (1, 0)
assert parse_series('5') == (0, 5)
def xpath_nth_child_function(self, xpath, function, last=False,
add_name_test=True):
try:
a, b = parse_series(function.arguments)
except ValueError:
raise ExpressionError("Invalid series: '%r'" % function.arguments)
# From https://www.w3.org/TR/css3-selectors/#structural-pseudos:
#
# :nth-child(an+b)
# an+b-1 siblings before
#
# :nth-last-child(an+b)
# an+b-1 siblings after
#
# :nth-of-type(an+b)
# an+b-1 siblings with the same expanded element name before
#
# :nth-last-of-type(an+b)
# an+b-1 siblings with the same expanded element name after
#
# So,
# for :nth-child and :nth-of-type
#
# count(preceding-sibling::<nodetest>) = an+b-1
#
# for :nth-last-child and :nth-last-of-type
#
# count(following-sibling::<nodetest>) = an+b-1
#
# therefore,
# count(...) - (b-1) ≡ 0 (mod a)
#
# if a == 0:
# ~~~~~~~~~~
# count(...) = b-1
#
# if a < 0:
# ~~~~~~~~~
# count(...) - b +1 <= 0
# -> count(...) <= b-1
#
# if a > 0:
# ~~~~~~~~~
# count(...) - b +1 >= 0
# -> count(...) >= b-1
# work with b-1 instead
b_min_1 = b - 1
# early-exit condition 1:
# ~~~~~~~~~~~~~~~~~~~~~~~
# for a == 1, nth-*(an+b) means n+b-1 siblings before/after,
# and since n ∈ {0, 1, 2, ...}, if b-1<=0,
# there is always an "n" matching any number of siblings (maybe none)
if a == 1 and b_min_1 <=0:
return xpath
# early-exit condition 2:
# ~~~~~~~~~~~~~~~~~~~~~~~
# an+b-1 siblings with a<0 and (b-1)<0 is not possible
if a < 0 and b_min_1 < 0:
return xpath.add_condition('0')
# `add_name_test` boolean is inverted and somewhat counter-intuitive:
#
# nth_of_type() calls nth_child(add_name_test=False)
if add_name_test:
nodetest = '*'
else:
nodetest = '%s' % xpath.element
# count siblings before or after the element
if not last:
siblings_count = 'count(preceding-sibling::%s)' % nodetest
else:
siblings_count = 'count(following-sibling::%s)' % nodetest
# special case of fixed position: nth-*(0n+b)
# if a == 0:
# ~~~~~~~~~~
# count(***-sibling::***) = b-1
if a == 0:
return xpath.add_condition('%s = %s' % (siblings_count, b_min_1))
expr = []
if a > 0:
# siblings count, an+b-1, is always >= 0,
# so if a>0, and (b-1)<=0, an "n" exists to satisfy this,
# therefore, the predicate is only interesting if (b-1)>0
if b_min_1 > 0:
expr.append('%s >= %s' % (siblings_count, b_min_1))
else:
# if a<0, and (b-1)<0, no "n" satisfies this,
# this is tested above as an early exist condition
# otherwise,
expr.append('%s <= %s' % (siblings_count, b_min_1))
# operations modulo 1 or -1 are simpler, one only needs to verify:
#
# - either:
# count(***-sibling::***) - (b-1) = n = 0, 1, 2, 3, etc.,
# i.e. count(***-sibling::***) >= (b-1)
#
# - or:
# count(***-sibling::***) - (b-1) = -n = 0, -1, -2, -3, etc.,
# i.e. count(***-sibling::***) <= (b-1)
# we we just did above.
#
if abs(a) != 1:
# count(***-sibling::***) - (b-1) ≡ 0 (mod a)
left = siblings_count
# apply "modulo a" on 2nd term, -(b-1),
# to simplify things like "(... +6) % -3",
# and also make it positive with |a|
b_neg = (-b_min_1) % abs(a)
if b_neg != 0:
b_neg = '+%s' % (b_neg)
left = '(%s %s)' % (left, b_neg)
expr.append('%s mod %s = 0' % (left, a))
xpath.add_condition(' and '.join(expr))
return xpath
def xpath_nth_child_function(self,
xpath,
function,
last=False,
add_name_test=True):
try:
a, b = parse_series(function.arguments)
except ValueError:
raise ExpressionError("Invalid series: '%r'" % function.arguments)
# From https://www.w3.org/TR/css3-selectors/#structural-pseudos:
#
# :nth-child(an+b)
# an+b-1 siblings before
#
# :nth-last-child(an+b)
# an+b-1 siblings after
#
# :nth-of-type(an+b)
# an+b-1 siblings with the same expanded element name before
#
# :nth-last-of-type(an+b)
# an+b-1 siblings with the same expanded element name after
#
# So,
# for :nth-child and :nth-of-type
#
# count(preceding-sibling::<nodetest>) = an+b-1
#
# for :nth-last-child and :nth-last-of-type
#
# count(following-sibling::<nodetest>) = an+b-1
#
# therefore,
# count(...) - (b-1) ≡ 0 (mod a)
#
# if a == 0:
# ~~~~~~~~~~
# count(...) = b-1
#
# if a < 0:
# ~~~~~~~~~
# count(...) - b +1 <= 0
# -> count(...) <= b-1
#
# if a > 0:
# ~~~~~~~~~
# count(...) - b +1 >= 0
# -> count(...) >= b-1
# work with b-1 instead
b_min_1 = b - 1
# early-exit condition 1:
# ~~~~~~~~~~~~~~~~~~~~~~~
# for a == 1, nth-*(an+b) means n+b-1 siblings before/after,
# and since n ∈ {0, 1, 2, ...}, if b-1<=0,
# there is always an "n" matching any number of siblings (maybe none)
if a == 1 and b_min_1 <= 0:
return xpath
# early-exit condition 2:
# ~~~~~~~~~~~~~~~~~~~~~~~
# an+b-1 siblings with a<0 and (b-1)<0 is not possible
if a < 0 and b_min_1 < 0:
return xpath.add_condition('0')
# `add_name_test` boolean is inverted and somewhat counter-intuitive:
#
# nth_of_type() calls nth_child(add_name_test=False)
if add_name_test:
nodetest = '*'
else:
nodetest = '%s' % xpath.element
# count siblings before or after the element
if not last:
siblings_count = 'count(preceding-sibling::%s)' % nodetest
else:
siblings_count = 'count(following-sibling::%s)' % nodetest
# special case of fixed position: nth-*(0n+b)
# if a == 0:
# ~~~~~~~~~~
# count(***-sibling::***) = b-1
if a == 0:
return xpath.add_condition('%s = %s' % (siblings_count, b_min_1))
expr = []
if a > 0:
# siblings count, an+b-1, is always >= 0,
# so if a>0, and (b-1)<=0, an "n" exists to satisfy this,
# therefore, the predicate is only interesting if (b-1)>0
if b_min_1 > 0:
expr.append('%s >= %s' % (siblings_count, b_min_1))
else:
# if a<0, and (b-1)<0, no "n" satisfies this,
# this is tested above as an early exist condition
# otherwise,
expr.append('%s <= %s' % (siblings_count, b_min_1))
# operations modulo 1 or -1 are simpler, one only needs to verify:
#
# - either:
# count(***-sibling::***) - (b-1) = n = 0, 1, 2, 3, etc.,
# i.e. count(***-sibling::***) >= (b-1)
#
# - or:
# count(***-sibling::***) - (b-1) = -n = 0, -1, -2, -3, etc.,
# i.e. count(***-sibling::***) <= (b-1)
# we we just did above.
#
if abs(a) != 1:
# count(***-sibling::***) - (b-1) ≡ 0 (mod a)
left = siblings_count
# apply "modulo a" on 2nd term, -(b-1),
# to simplify things like "(... +6) % -3",
# and also make it positive with |a|
b_neg = (-b_min_1) % abs(a)
if b_neg != 0:
b_neg = '+%s' % (b_neg)
left = '(%s %s)' % (left, b_neg)
expr.append('%s mod %s = 0' % (left, a))
xpath.add_condition(' and '.join(expr))
return xpath
