Fix XPath variable handling and invalid value contamination#342
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Pull request overview
This PR adjusts REXML’s XPath evaluation to prevent nil/invalid values from “contaminating” results, primarily by making id() return an empty node-set and by coercing variable values + applying remaining predicates/steps after variable/group evaluation.
Changes:
- Make unimplemented XPath function
id()return[](empty node-set) instead ofnil. - Add variable coercion and ensure remaining predicates/steps are applied after variable and grouped expressions.
- Add/extend tests covering
id()and variable handling (including invalid predicate application on non-node-set variables).
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| test/xpath/test_base.rb | Adds regression tests for id() and variable coercion/predicate behavior. |
| lib/rexml/xpath_parser.rb | Implements variable coercion and applies remaining predicates after variable/group evaluation. |
| lib/rexml/functions.rb | Changes id() to return an empty node-set ([]). |
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| def coerce_variable(value) | ||
| case value | ||
| when Array | ||
| value.grep(REXML::Node).uniq | ||
| when Numeric, String, true, false | ||
| value | ||
| else | ||
| "" | ||
| end | ||
| end |
| assert_equal(["e"], XPath.match(doc, "//e[preceding-sibling::* = '1']").map(&:name)) | ||
| end | ||
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| def test_unimplemented_id_shouldnot_contaminate_nil |
Fix nil and other invalid value contamination. Nil can be injected through variables and through id function. Unimplemented function `id()` is fixed to return `[]` instead of `nil`. Add variable coerce and predicates after variables.
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Fix nil and other invalid value contamination. Nil can be injected through variables and through id function.
Unimplemented function
id()is fixed to return[]instead ofnil.Add variable coerce and predicates after variables.
Minor behavior changes for an invalid XPath match:
It may raise TypeError (because
$xwasn't evaluated to a nodeset), though, it shoudn't return[42]Note
Although nodeset as a variable has been accepted before, the code added in pull request explicitly permits it.
Nokogiri only accepts string value as a variable, so there's an option to limit the value types here.
Accepting nodeset may cause a problem if the passed nodes doesn't belong to a single document root. (or just consider such case as unsupported)