difflens

Ah yea we had the same thought a while back so, yes, that's in the works :) The biggest drawback here is that there are rate limits to the GitHub API. It should work for just trying out some diffs though. Thanks for the feedback!

Great post. I'm in the early days of trying to get DiffLens (https://github.com/marketplace/difflens) off the ground and saw myself nodding along to so many points! Having a boring backend service that pays is a gold mine.

Done. Thanks for the feedback about the screenshots. That makes sense! I'll update the text to include the demo :) Let me know if you have thoughts on the app itself!

Hi HN! We were frustrated with text diffs on GitHub PRs, so we made DiffLens (https://github.com/marketplace/difflens) to produce language aware diffs on PRs. DiffLens constructs an Abstract Syntax Tree for each file, and uses that semantic information to intelligently diff changes. Checkout the demo on our website (https://www.difflens.com). If you review code, especially TypeScript, JavaScript or CSS, give DiffLens a try, it's free!

We're looking for feedback from developers. If you share our frustrations with reviewing code changes, we'd love to talk to you. Most developers already have a favourite diff tool installed locally but there exists very little for reviewing code changes online, so we worked on DiffLens slowly over a number of years. We use it to review our own code changes, and we love it. We'd really appreciate thoughts and insights about the idea and its execution from developers and will answer any questions that come up. Thanks for reading!

DiffLens developers here! (https://github.com/marketplace/difflens) We current use ACE for our editors, but we've always been interested in checking out CodeMirror too. When we initially started work on DiffLens, CodeMirror 6.0 wasn't "ready" yet, so we chose ACE. Congrats on the release! CodeMirror is so full of features.

FWIW, here's a repo of ANTLR grammars: https://github.com/antlr/grammars-v4

Many of them are incomplete, but it gives a good idea of how the grammar looks for ANTLR.

I used the ANTLR grammar for parsing CSS in DiffLens (https://github.com/marketplace/difflens). DiffLens uses the typescript compiler itself to parse TS and JS.

I've also used Roslyn to parse C# (and F#). I wonder if the ruby compiler itself exposes a parser.

I'm most familiar with specifying grammar for the ANTLR tool. Just out of curiosity, is the antlr grammar a parsing expression grammar? Does anyone know?

Separately, I'm curious about how a parser generated out of ANTLR/yacc etc compares to this hand written one? If you've done some benchmarking, it'd be great to see numbers!

I wouldn't consider this cheating, I would rather call this preparation. Is looking at question banks before an exam considered cheating? I think this is in the same vein. Interviewers are people too, everyone knows there is a finite, albeit large, pool of questions to ask. If I ever see a candidate that has prepared to the point that he/she can code up the answer to the majority of leetcode style questions, I'd hire them without hesitation.

Perhaps I don't understand their use case fully, but it seems to me that every schema can be defined as a child protobuf message, and each child can then be added to a oneof field of a parent protobuf message. This way, you get the strict/optional type checks that are required, and the efficiency and ecosystem around protobufs.

Just plugging difflens here: https://github.com/marketplace/difflens

If you work primarily with frontend technologies and want a syntax aware diff on GitHub PRs, difflens might be right up your alley! Standalone Mac and Windows apps are coming out soon.

Can I just say that I appreciate the transparency about your numbers here! As a bootstrapped SAAS builder here, this gives me perspective

If you have a few minutes, can you list a few of these problems? Just curious here!

Difflens (https://github.com/marketplace/difflens) is a step in this direction. It produces syntax aware diffs for TS/JS and CSS at the moment.

I have! I've always found GitHub's default diff to be annoying to track changes. I needed a way to align the left and right editors right next to each other so I could get context. So I wrote an app and published it on the GitHub marketplace: https://github.com/marketplace/difflens. I use it everyday and have other (regular) users too. It's free to try