Fix xpath parsing xpath that has string literal containing parentheses and brackets

[tompng]

String literal in XPath 1.0 doesn't have escapes.
begin end while cond is not a normal modifier while, but a do-while loop. (I didn't know it). REXML uses this syntax in several files.

Removes preprocessing that removes spaces with gsub which may wrongly modifies string literal.
Also fixes error parsing //a[1] [2].
All test except exact-error-message test and the one I added in this PR passed with:

def parse path
  path = path.gsub('(', '( ').gsub(/[\)\[\]]/, ' \0 ') # Insert space around paren/bracket

REF: https://www.w3.org/TR/xpath-10/#exprlex

For readability, whitespace may be used in expressions even though not explicitly allowed by the grammar: ExprWhitespace may be freely added within patterns before or after any ExprToken.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR improves XPath parsing robustness around whitespace handling, especially when spaces appear inside string literals, and adds regression tests to cover these cases.

Changes:

• Add tests validating that extra whitespace in XPath expressions is treated as ignorable where appropriate.
• Update XPathParser#parse to strip ignorable spaces without altering whitespace inside quoted string literals.
• Update group parsing to ignore parentheses/brackets that appear inside quoted string literals.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
test/xpath/test_base.rb	Adds test coverage for whitespace normalization and for bracket/paren characters inside XPath string literals.
lib/rexml/parsers/xpathparser.rb	Refactors space-stripping into a helper that respects string literals; improves grouping logic to ignore delimiters inside quotes.

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