Question 1

How do I use look-ahead assertions in fancy-regex?

Accepted Answer

Fancy-regex supports look-ahead and look-behind assertions using standard syntax like (?=...) for positive look-ahead. You can test patterns in the online playground to ensure compatibility, and refer to the documentation for Rust API usage examples.

Question 2

Fancy-regex or the regex crate: which should I use for my Rust project?

Accepted Answer

Use fancy-regex if you need advanced features like look-around or backreferences, as the regex crate doesn't support them. For basic regex patterns without these features, the regex crate is more efficient and stable, with better worst-case performance guarantees.

Question 3

Does fancy-regex fully support all Oniguruma syntax?

Accepted Answer

It aims for compatibility with Oniguruma when the relevant flag is set, but check the documentation for any limitations, as the README notes it's still in development and may not cover all edge cases or recursive features.

Question 4

What are the performance implications of using backreferences in fancy-regex?

Accepted Answer

Backreferences require backtracking and can lead to exponential worst-case performance, as fancy-regex delegates only when possible. The README warns about denial-of-service risks, so use them cautiously in non-critical paths.

Question 5

Can fancy-regex handle syntax highlighting for text editors like VS Code?

Accepted Answer

Yes, it's designed for compatibility with TextMate-style grammars that use Oniguruma features, making it suitable for building editors or IDEs in Rust. However, ensure your patterns don't rely on missing features like recursive backreferences.

Question 6

Is fancy-regex ready for production use?

Accepted Answer

It's functional for many use cases, but the README notes it's still in development with missing features and performance caveats. Evaluate based on your needs—for critical applications, test thoroughly and consider the trade-offs.

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