Daniel Sun created GROOVY-12133:
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Summary: Implement matchBalanced utility to support Regex Balanced
Groups
Key: GROOVY-12133
URL: https://issues.apache.org/jira/browse/GROOVY-12133
Project: Groovy
Issue Type: Improvement
Reporter: Daniel Sun
Fix For: 6.0.0-beta-1
h3. *Description*
*Context*
Java's native regex engine lacks C#-style balanced group support (pushdown
automaton). This makes parsing infinitely nested structures (e.g., nested
parentheses, HTML tags, or code blocks) notoriously difficult, often leading to
ReDoS (Regular Expression Denial of Service) vulnerabilities if solved purely
via regex.
*Proposed Solution*
Introduce a highly optimized {{matchBalanced}} method. It should use a
single-pass, stack-based scanner with dynamic subsumption (tail-absorption) to
mimic C# balanced group behavior while guaranteeing O(N) performance.
*Acceptance Criteria*
* *Core Extraction:* Correctly extracts the outermost balanced groups from
deeply nested strings (e.g., {{(A + (B * C))}} extracts the entire block).
* *Fault Tolerance:* Gracefully handles malformed/dangling boundaries
(unmatched open or close tags) without polluting the stack or crashing.
* *Ignore Options:* Supports an {{ignoreRegex}} configuration to safely bypass
escaped boundaries or string literals (e.g., ignoring {{"{}"}} inside quotes).
* *Edge Stripping:* Supports an {{includeEdges}} configuration to optionally
strip the outer boundary tags from the result.
* *Performance:* Must guarantee strict O(N) time complexity. No backtracking,
recursion, or expensive sorting operations are allowed.
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