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Reject underscored XPath function names #366

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Reject underscored XPath function names #366

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364d6a2
Reject underscored XPath function names
sjh9714 Aug 30, 2026
cc8ee2a
Preserve underscored XPath functions by default
sjh9714 Aug 30, 2026
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5 changes: 5 additions & 0 deletions lib/rexml/parsers/xpathparser.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,10 @@ class XPathParser # :nodoc:
include XMLTokens
LITERAL = /^'([^']*)'|^"([^"]*)"/u

def initialize(strict: false)
@strict = strict
end

def namespaces=( namespaces )
Functions::namespace_context = namespaces
@namespaces = namespaces
Expand Down Expand Up @@ -653,6 +657,7 @@ def PrimaryExpr path, parsed
#arry << @variables[ varname ]
when /^(\w[-\w]*)(?:\()/
fname = $1
return path if @strict && fname.include?("_")

@tompng tompng Aug 31, 2026

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The mechanism that this return path rejects the xpath, is complicated. (See LocationPath → RelativeLocationPath → NodeTest called when 'local_name()' is passed)

I think underscored function names are invalid not because it has underscore, but because it's not registered as a function in XPath 1.0 spec.
Both examples in the code below is in the same situation: using unknown function, so the result (return value or raised error) should be the same.

REXML::XPath.match(REXML::Document.new('<root/>'), 'local_name()')
REXML::XPath.match(REXML::Document.new('<root/>'), 'localname()')

From a viewpoint of module's responsibility, I personally think this check shouldn't be done in REXML::Parsers:XPathParser, but in one of:

  • REXML::XPathParser: layer that converts '-' to '_', function name to a method name
  • REXML::FunctionsClass: layer that knows all available functions, checks if a method name is registered as a function

tmp = $'
return path if fname =~ NT
path = tmp
Expand Down
2 changes: 1 addition & 1 deletion lib/rexml/xpath_parser.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,7 @@ class XPathParser

def initialize(strict: false)
@debug = DEBUG
@parser = REXML::Parsers::XPathParser.new
@parser = REXML::Parsers::XPathParser.new(strict: strict)
@namespaces = nil
@variables = {}
@functions = FunctionsClass.new
Expand Down
9 changes: 8 additions & 1 deletion test/functions/test_base.rb
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Expand Up @@ -290,11 +290,18 @@ def test_string_nil_without_context
{"n" => nil}))
end

def test_unregistered_method
def test_unregistered_method_with_underscore
doc = Document.new("<root/>")
assert_nil(XPath::first(doc.root, "to_s()"))
end

def test_unregistered_method_with_underscore_in_strict_mode
doc = Document.new("<root/>")
assert_raise(REXML::ParseException) do
XPath::first(doc.root, "to_s()", nil, {}, strict: true)
end
end

def test_nonexistent_function
doc = Document.new("<root><nonexistent/></root>")
# TODO: Maybe, this is not XPath spec behavior.
Expand Down
13 changes: 13 additions & 0 deletions test/parser/test_xpath.rb
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
# frozen_string_literal: false

require "test/unit"
require "rexml/parseexception"
require "rexml/parsers/xpathparser"

module REXMLTests
Expand Down Expand Up @@ -66,6 +67,18 @@ def test_function
abbreviate("string-length(a/b[last()])"))
end

def test_function_with_underscore
assert_equal("local_name(*)",
abbreviate("local_name(*)"))
end

def test_function_with_underscore_in_strict_mode
parser = REXML::Parsers::XPathParser.new(strict: true)
assert_raise(REXML::ParseException) do
parser.abbreviate("local_name(*)")
end
end

def test_descendant_or_self_only
assert_equal("//",
abbreviate("/descendant-or-self::node()/"))
Expand Down