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Fixed processing of nested predicates. 

This ensures that nested predicates and functions that depend on predicates are
processed correctly.
This commit is contained in:
Yorick Peterse 2014-09-03 20:56:07 +02:00
parent 3196050978
commit bd31379c85
2 changed files with 51 additions and 97 deletions
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119
lib/oga/xpath/evaluator.rb
View File

@ -11,19 +11,19 @@ module Oga
# for more information). It is however perfectly fine to use multiple
# separated instances as this class does not use a thread global state.
#
# ## Node Stack
# ## Node Set Stack
#
# This class uses an internal stack of XML nodes. This stack is used for
# certain XPath functions that require access to the current node being
# processed in a predicate. An example of such a function is `position()`.
# This class uses an internal stack of XML node sets. This stack is used for
# functions that require access to the set of nodes a predicate belongs to.
# An example of such a function is `position()`.
#
# An alternative to a stack would be to pass the current node as arguments
# to the various `on_*` methods. The problematic part of this approach is
# that it requires every method to take and pass along the argument. It's
# far too easy to make mistakes in such a setup and as such I've chosen to
# use an internal stack instead.
# An alternative would be to pass the node sets a predicate belongs to as an
# extra argument to the various `on_*` methods. The problematic part of
# this approach is that it requires every method to take and pass along the
# argument. It's far too easy to make mistakes in such a setup and as such
# I've chosen to use an internal stack instead.
#
# See {#with_node} and {#current_node} for more information.
# See {#with_node_set} and {#current_node_set} for more information.
#
# ## Set Indices
#
@ -66,8 +66,8 @@ module Oga
#
def initialize(document, variables = {})
@document = document
@nodes = [[]]
@variables = variables
@node_sets = []
end
##
@ -147,7 +147,6 @@ module Oga
def on_path(ast_node, context)
nodes = XML::NodeSet.new
with_node_stack do
ast_node.children.each do |test|
nodes = process(test, context)
@ -157,7 +156,6 @@ module Oga
context = nodes
end
end
end
return nodes
end
@ -174,34 +172,31 @@ module Oga
nodes = XML::NodeSet.new
predicate = ast_node.children[2]
context.each do |xml_node|
nodes << xml_node if node_matches?(xml_node, ast_node)
end
context.each_with_index do |xml_node, index|
next unless node_matches?(xml_node, ast_node)
# Filter the nodes based on the predicate.
if predicate
new_nodes = XML::NodeSet.new
nodes.each_with_index do |current, index|
xpath_index = index + 1
retval = with_node(current) { process(predicate, nodes) }
retval = with_node_set(context) do
process(predicate, XML::NodeSet.new([xml_node]))
end
# Numeric values are used as node set indexes.
if retval.is_a?(Numeric)
new_nodes << current if retval.to_i == xpath_index
nodes << xml_node if retval.to_i == xpath_index
# Node sets, strings, booleans, etc
elsif retval
# Empty strings and node sets evaluate to false.
if retval.respond_to?(:empty?) and retval.empty?
next
end
new_nodes << current
nodes << xml_node
end
else
nodes << xml_node
end
nodes = new_nodes
end
return nodes
@ -492,13 +487,9 @@ module Oga
def on_axis_self(ast_node, context)
nodes = XML::NodeSet.new
if current_node
nodes << current_node if node_matches?(current_node, ast_node)
else
context.each do |context_node|
nodes << context_node if node_matches?(context_node, ast_node)
end
end
return nodes
end
@ -883,7 +874,7 @@ module Oga
#
def on_call_last(context)
# XPath uses indexes 1 to N instead of 0 to N.
return context.length.to_f
return current_node_set.length.to_f
end
##
@ -894,7 +885,7 @@ module Oga
# @return [Float]
#
def on_call_position(context)
index = context.index(current_node) + 1
index = current_node_set.index(context.first) + 1
return index.to_f
end
@ -1044,7 +1035,7 @@ module Oga
convert = convert[0]
end
else
convert = current_node
convert = context.first
end
if convert.respond_to?(:text)
@ -1087,7 +1078,7 @@ module Oga
convert = exp_retval
end
else
convert = current_node.text
convert = context.first.text
end
return to_float(convert)
@ -1395,7 +1386,7 @@ module Oga
#
def on_call_lang(context, language)
lang_str = on_call_string(context, language)
node = current_node
node = context.first
while node.respond_to?(:attribute)
found = node.attribute('xml:lang')
@ -1560,7 +1551,7 @@ module Oga
raise TypeError, 'only node sets can be used as arguments'
end
else
node = current_node
node = context.first
end
return node
@ -1717,65 +1708,31 @@ module Oga
end
##
# Stores the node in the node stack, yields the block and removes the node
# from the stack.
#
# This method is mainly intended to be used when processing predicates.
# Expressions inside a predicate might need access to the node on which
# the predicate is performed.
#
# This method's return value is the same as whatever the block returned.
# Stores the specified node set and yields the supplied block. The return
# value of this method is whatever the block returned.
#
# @example
# some_node_set.each do |node|
# result = with_node(node) { process(...) }
# retval = with_node_set(context) do
# process(....)
# end
#
# @param [Oga::XML::Node] node
# @return [Mixed]
# @param [Oga::XML::NodeSet] nodes
#
def with_node(node)
node_stack << node
def with_node_set(nodes)
@node_sets << nodes
retval = yield
node_stack.pop
@node_sets.pop
return retval
end
##
# Adds a new stack for storing context nodes and yields the supplied
# block.
# @return [Oga::XML::NodeSet]
#
# The return value of this method is whatever the supplied block returns.
#
# @return [Mixed]
#
def with_node_stack
@nodes << []
retval = yield
@nodes.pop
return retval
end
##
# Returns the current node that's being processed.
#
# @return [Oga::XML::Node]
#
def current_node
return node_stack.last
end
##
# @return [Array]
#
def node_stack
return @nodes.last
def current_node_set
return @node_sets.last
end
end # Evaluator
end # XPath

11
spec/oga/xpath/evaluator/general_spec.rb
View File

@ -8,14 +8,15 @@ describe Oga::XPath::Evaluator do
context '#function_node' do
before do
@context_set = Oga::XML::NodeSet.new([@document])
@document = parse('<root><a>Hello</a></root>')
@context_set = @document.children
end
example 'return the first node in the expression' do
exp = s(:axis, 'child', s(:test, nil, 'a'))
node = @evaluator.function_node(@context_set, exp)
node.should == @document.children[0]
node.should == @context_set[0].children[0]
end
example 'raise a TypeError if the expression did not return a node set' do
@ -26,11 +27,7 @@ describe Oga::XPath::Evaluator do
end
example 'use the current context node if the expression is empty' do
a_node = @document.children[0]
@evaluator.stub(:current_node).and_return(a_node)
@evaluator.function_node(@context_set).should == a_node
@evaluator.function_node(@context_set).should == @context_set[0]
end
end