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Difftastic: A diff that understands syntax

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Re: Difftastic: A diff that understands syntax

#191

Post by dools »

Funny side note: I had a flat mate once who was on a working holiday from Japan.

He was in love with and endlessly curious about English slang, it’s basically all we talked about.

I remember explaining to him why my uni friends and I referred to things as being “craptastic”, starting with American marketing’s love affair with the portmanteau.

He got it pretty quickly and enjoyed using it in conversation.

The saying that was harder for him to understand was “fuck all”. He always wanted fuck to be the verb, rather than using “fuck all” as the adjective, so he would say things like “I fuck all my money last night at the pub”.

Re: Difftastic: A diff that understands syntax

#192

Post by giraffe_lady »

munk-a wrote: post #176
gmfawcett wrote: post #119

Earlier quoted context omitted.

A wild nitpicker appears. I understand where you're coming from & why this matters. But Go, the language spec, doesn't make any guarantees about struct layout at all. A layout difference may be meaningful, practically, but it's potentially unreliable. e.g. see https://groups.google.com/g/golang-nuts/c/1BlZDNBLiAM Having said that: if a Go compiler for a given architecture decided to change its layout algorithm, I'm p…

PHP long stated that associative array sorting order was unstable and not guaranteed (especially when the union (+) operator or array_merge function were involved) - that doesn't mean ten bazillion websites wouldn't instantly break if they ever actually changed the ordering to be unpredictable. Language designers need to contend with the fact that the ultimate final say in whether a thing is or not is whether that be…

Didn't ruby actually do exactly this though? And it broke a million websites and they changed it back in the next version and have made it explicit ever since? To me that is much stronger evidence than what we think would happen if php did it.

Re: Difftastic: A diff that understands syntax

#193

Post by db48x »

RyEgswuCsn wrote: post #37
danbruc wrote: post #12

Earlier quoted context omitted.

Because it is much easier, you don't have to build and maintain parsers for hundreds of languages. And you don't need need just any parser, you need very robust ones that can deal with malformed files well. Or, if you only pick a small set of supported languages, your diff tool will not work on most files or have to fall back to a structure-agnostic algorithm. Also not all text files even follow any useful grammar at…

> And you don't need need just any parser, you need very robust ones that can deal with malformed files well. I very much agree. I feel there has been a trend recently where people (re)discovered how cool and useful ASTs are and now expect everything be using them. I suspect old-school computer scientists might be secretly laughing at this while programming with some Lisp-like languages they invented for themselves.…

What you do is produce an AST where some nodes indicate syntax errors. This works best in languages where it is easy to resynchronize after an error, of course.

Re: Difftastic: A diff that understands syntax

#194

Post by giraffe_lady »

ummonk wrote: post #180
zukzuk wrote: post #122

Earlier quoted context omitted.

I wrote a masters thesis about the more general problem here ( https://tspace.library.utoronto.ca/bitstream/1807/65616/11/Z... ). The tl;dr is that there's an almost infinite number of ways to atomize/conceptualize code into meaningful "units" (to "register" it, in my supervisor's words), and the most appropriate way to do that is largely perspectival — it depends on what you care about after the fact, and there is n…

I mean to have an improvement over the status quo we need to simply find a conception that works better than lines as units of code. Let’s not let perfect be the enemy of the good.

love to tell someone who literally wrote a masters thesis on a topic what we need to "simply do" to solve it lol. I almost want to admire the confidence but

Re: Difftastic: A diff that understands syntax

#196

Post by pie_flavor »

adolph wrote: post #103
pie_flavor wrote: post #59

Earlier quoted context omitted.

This exact project is called JetBrains MPS.

MPS seems to be a DSL authoring tool. How would this be used to make an AST diff tool? https://www.jetbrains.com/mps/ https://en.wikipedia.org/wiki/Abstract_syntax_tree

Well, the comment I was responding to was about storing the AST, not diffing it. If that's what you meant the one follows naturally from the other. Once the file format is the AST instead of its visual representation, it makes sense to implement lots of operations as DSL extensions instead of library features, because the language is the library in a sense. MPS is marketed as a DSL tool but what really is is a projectional language tool.

Re: Difftastic: A diff that understands syntax

#197

Post by krick »

Understanding syntax would be really amazing for merges (not sure if it's even possible), but for diffs I don't immediately see why I should use that over simpler syntax-unaware tools. Highlighting the actual change in a string is important, and so is ignoring whitespace, but diffsofancy -w does it just fine. What else would I need? (Well, I guess the only use-case I can see from the demo is 2 compact changes in a single line, but… meh.)

On the other hand, even though my diffs are usually not that huge, sometimes they might be, and I don't want to switch tools every time that happens (I have just git alias and I don't even remember my exact config, nor should I care). So being slow is not great.

Re: Difftastic: A diff that understands syntax

#198

Post by db48x »

Myrmornis wrote: post #142
yewenjie wrote: post #140

Does a `magit` plugin exist for Emacs users? The author of this package is also the author of a couple of popular Emacs packages but I did not see any mention of Emacs.

It won't be able to form the basis of a magit plugin because it does not target traditional diff format.

To be more precise, Magit could easily display the output of difft, but Magit wants to be able to do more than that. You can navigate diffs by hunk and by file, you can collapse hunks and files, you can even select individual lines of the diff to stage or unstage them, apply or unapply them, etc. Strictly speaking that’s probably not impossible with difft, but because difft has the explicit goal of displaying diffs to humans rather than producing machine–parsable output, it won’t be easy. I still want it to happen though.

Re: Difftastic: A diff that understands syntax

#199

Post by chlorion »

adwn wrote: post #111
loxias wrote: post #80

Earlier quoted context omitted.

> curl https://sh.rustup.rs -sSf | sh hard pass :)

> hard pass Why? You're willing to run some random open source project, but you're not willing to run the official Rust installation script?

I feel the same way, I am just not willing to pipe curl into a shell blindly.

Even if this specific instance of curl'ing into sh is safe, or if I download and then run it, it's still extremely poor practice and gives me serious doubts about the developers and their security practices in general.

I also do not like when every project decides to poorly reimplement the package manager. If every software used it's own package manager my system would be a complete mess with dozens of different package managers fighting each other and it would be a total nightmare to update the system or manage non-trivial dependency chains when installing something new.

Rust is one of my favorite languages but this is definitely my least favorite aspect of it all. It really feels like the developers "optimized" for systems with no package manager.

Re: Difftastic: A diff that understands syntax

#200

Post by benreesman »

dools wrote: post #191

Funny side note: I had a flat mate once who was on a working holiday from Japan. He was in love with and endlessly curious about English slang, it’s basically all we talked about. I remember explaining to him why my uni friends and I referred to things as being “craptastic”, starting with American marketing’s love affair with the portmanteau. He got it pretty quickly and enjoyed using it in conversation. The saying t…

I know native English-speakers who would say that s/pub/bar/.

Profanity is just delightful in general, and non-native English speakers come up with some of the best profane idioms in English.

I wonder if it’s the same in other languages?

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