regex-tools/docs/FLAVOUR_SUPPORT.md

Flavour support

Version 0.4.1 exposes twelve executable profiles. “Partial lexical provider” means that Regex Tools recognizes common structure and replacement tokens for explanation only; the named runtime compiler and replacement operation remain authoritative.

Profile	Syntax and execution identity	Replacement	Captures and native offsets
JavaScript (ECMAScript)	regexpp 4.12.2 with ECMAScript 2025 syntax; current browser RegExp executes	Bounded ECMAScript GetSubstitution	Named/numbered, final repeated capture; UTF-16
PCRE2	Partial provider; official standalone PCRE2 10.47 8-bit WASM executes in mandatory UTF/UCP mode	Native bounded pcre2_substitute() loop	Native named/numbered records, no history; UTF-8 bytes
PHP	Partial provider; actual PHP 8.5.8 preg_* in @php-wasm/web-8-5 3.1.46, reporting PCRE2 10.44	Fixed bounded PHP-token expansion; load-time preg_replace() parity	Native named/numbered records, no history; UTF-8 bytes
Perl	Partial provider; actual Perl 5.28.1 through legacy WebPerl 0.09-beta	Fixed bounded literal/$$/$n/${name} expansion; arbitrary Perl expressions unavailable	Native numbered spans plus bounded name annotations, no history; Unicode code points
Python	Partial provider; CPython 3.14.2 re in Pyodide 314.0.3	Native bounded re expansion	Native named/numbered spans, no history; Unicode code points
Ruby	Partial provider; CRuby 4.0.0 Regexp in ruby.wasm 2.9.3-2.9.4	Native gsub/sub iteration plus bounded CRuby 4.0.0-compatible expansion	Native named/numbered spans, no history; Unicode code points
Java	Partial provider; TeaVM 0.15.0 java.util.regex, not OpenJDK	TeaVM single-digit $n; no ${name}	Native numbered ranges plus lexical names, no history; UTF-16
C++	Partial provider; Emscripten 6.0.4 libc++ std::wregex; modified ECMAScript grammar by default	Fixed bounded formatter; load-time libc++ match.format parity	Numbered captures only, no history; 32-bit wchar_t code points
Go	Partial provider; Go 1.26.5 standard-library regexp with RE2 syntax	Fixed bounded expansion; load-time regexp.ExpandString parity	Native named/numbered records, no history; UTF-8 bytes
Rust	Partial provider; Rust regex crate 1.13.1, built with rustc 1.97.1	Fixed bounded expansion; load-time Captures::expand parity	Native named/numbered records, no history; UTF-8 bytes
.NET	Partial provider; .NET 10.0.10 System.Text.RegularExpressions, invariant culture	Fixed streaming .NET-token expansion with load-time native Match.Result parity	Named/numbered final records, no capture history in this adapter; UTF-16
Scala/JVM compatibility	Partial provider; explicitly shares TeaVM 0.15.0 java.util.regex; no Scala runtime	Same TeaVM single-digit $n subset; no ${name}	Same ranges as the TeaVM Java adapter; UTF-16

Flags and options

• JavaScript exposes g, i, m, s, u, v, y and d; u and v are mutually exclusive.
• Standalone PCRE2 exposes application iteration g plus i, m, s, x, U and J, with match-step, depth and heap limits. UTF/UCP is mandatory.
• PHP exposes application iteration g plus the reviewed preg modifiers i, m, s, x, u, U, A, D, J, n and r. PHP's u is not conflated with standalone PCRE2's mandatory UTF/UCP configuration.
• Legacy Perl exposes g, i, m, s, x, n and one of a, d, l or u. The two-character /aa mode is not exposed.
• Python exposes application iteration g plus a, i, m, s and x.
• Ruby exposes application iteration g plus i, m and x; Ruby m includes dot-all behavior.
• Java and Scala compatibility expose application iteration g plus TeaVM Pattern flags i, d, m, s, u, x and the documented U compatibility request.
• C++ exposes application iteration g plus i, n, o and c, and a required grammar option: ECMAScript, basic, extended, awk, grep or egrep.
• Go exposes application iteration g plus i, m, s and U.
• Rust exposes application iteration g plus i, m, s, U, u, x and R; Unicode is enabled by default.
• .NET exposes application iteration g plus i, m, s, n, x, r, c and b. Execution is always culture invariant; c makes that fixed compatibility choice explicit.

Verified boundaries

Every adapter has focused identity, request and result-contract tests. Conformance and browser suites exercise compilation errors, bounded matching, zero-length iteration, range normalization, replacement and worker recovery across the profile set. Pack verifiers additionally check self-hosted assets, metadata, closed-file-set checksums and applicable licences/notices.

TeaVM supplies an Apache Harmony-derived class library. It is not OpenJDK and does not implement OpenJDK Pattern.UNICODE_CHARACTER_CLASS; U means the documented TeaVM compatibility behavior in both the Java and Scala profiles. The Scala profile also does not implement scala.util.matching.Regex wrapper or extractor APIs.

The Perl target is intentionally legacy. Its unmodified WebPerl loader contains one eval(code) site in an optional Perl-to-JavaScript interoperability import. The fixed Regex Tools bridge does not load that facility, accepts pattern and replacement values only as JSON data, uses no re 'eval', rejects (?{...}) and (??{...}), and passes the documented CSP smoke without broad 'unsafe-eval'.

Feature scope

Static findings, bounded growth probes, benchmarks, generated cases and formatting are ECMAScript-only. Generated-case version 1 requires the complete accepted regexpp AST and verifies every retained label through the actual browser engine. No partial provider is passed through that generator or formatter.

Automatic-callout tracing and reviewed C17 code generation are standalone PCRE2-only. The PHP profile does not reuse the standalone PCRE2 10.47 trace or code-generation path because its authoritative engine is PHP preg with PCRE2 10.44.

Exact-request semantic comparison and subject minimization support only their reviewed ECMAScript/standalone-PCRE2 paths. Other selections are disabled rather than routed through another profile. Results never claim generic twelve-way equivalence.