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Difftastic: A diff that understands syntax

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Re: Difftastic: A diff that understands syntax

#71

Post by gkfasdfasdf »

loxias wrote: post #22

This looks really cool and I can't wait to try it, tho... a bit of a PITA to get running. ;) Took a while to figure out how to build, and had to install 400MB of dependencies first.... Edit: And after installing cargo, watching it fail to build, then determining I must need a newer version of cargo, so I built that from source... it fails. Apparently I need to install `rustc-mozilla` and not `rustc`. "obviously". Thi…

Using ubuntu 20.04, I first installed cargo:

  curl https://sh.rustup.rs -sSf | sh
Restart shell to get $HOME/.cargo/bin in PATH, then did:

  cargo install difftastic
And ~4 minutes later, difft executable is ready.

Agree though that some pre-built binaries would be fantastic!

Re: Difftastic: A diff that understands syntax

#72

Post by jhgb »

danbruc wrote: post #48
RyEgswuCsn wrote: post #37

Earlier quoted context omitted.

> 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.…

With only basic knowledge in the domain I would assume it is hard and ugly. If the file is malformed, there is almost certainly an infinite number of possible edits to make the file adhere to the grammar, hence there can not be any algorithm that just provides the one and only correct syntax tree. This in turn means that you have to come up with heuristics that identify reasonable changes which fix the file and that…

"If the file is malformed, there is almost certainly an infinite number of possible edits to make the file adhere to the grammar, hence there can not be any algorithm that just provides the one and only correct syntax tree. This in turn means that you have to come up with heuristics that identify reasonable changes which fix the file and that is probably not easy."

Don't we call such heuristics "test suites"?

Re: Difftastic: A diff that understands syntax

#73

Post by vanderZwan »

narush wrote: post #25
vcmiraldo wrote: post #10

I really like the idea of focusing on producing patches for human consumption. I studied the problem of merging AST-level patches during my PhD ( https://github.com/VictorCMiraldo/hdiff ) and can confirm: not simple! :)

Can you give a little color on where the difficulties lie? Is it an efficiency question, or is determining "which changes" hard in the first place?

Early in the linked thesis there is a one-page argument about the shortcomings of traditional approaches, which technically isn't what you asked but might still answer the side of the question that deals with human usage at least:

https://victorcmiraldo.github.io/data/MiraldoPhD.pdf#page=24

Re: Difftastic: A diff that understands syntax

#78

Post by loxias »

gkfasdfasdf wrote: post #71
loxias wrote: post #22

This looks really cool and I can't wait to try it, tho... a bit of a PITA to get running. ;) Took a while to figure out how to build, and had to install 400MB of dependencies first.... Edit: And after installing cargo, watching it fail to build, then determining I must need a newer version of cargo, so I built that from source... it fails. Apparently I need to install `rustc-mozilla` and not `rustc`. "obviously". Thi…

Using ubuntu 20.04, I first installed cargo: curl https://sh.rustup.rs -sSf | sh Restart shell to get $HOME/.cargo/bin in PATH, then did: cargo install difftastic And ~4 minutes later, difft executable is ready. Agree though that some pre-built binaries would be fantastic!

Ah, well, if you're willing to accept having a frankensystem with a mix of packaged and unpackaged software, sure. ;) I used to do that, back in Slackware days.

It's considered really sloppy and unmaintainable to admin a system like that. Things quickly get out of hand.

That strategy _does_ work if you isolate it to a chroot or a container, but littering /usr/local with all sorts of locally compiled upstream is just asking for future pain. Security updates, library incompatibilities, &c.

Prebuilt binaries might be nice, but I don't expect them for random projects. (and I wouldn't have used them if offered) I do think it's a reasonable expectation to be able to build software w/o essentially setting up a new userland just for that tool though. :)

Re: Difftastic: A diff that understands syntax

#79

Post by oauea »

sanity31415 wrote: post #76

Unfortunately it's closed source, but https://www.semanticmerge.com/ has been around for a few years and works similarly, but can also merge.

I just spent a few minutes on that site and I can't even figure out how to try it out, or their pricing, or anything other than some very superficial docs, really.

Is this just a pretty website, or is the software actually available anywhere?

Re: Difftastic: A diff that understands syntax

#80

Post by loxias »

lopatin wrote: post #67
loxias wrote: post #58

Earlier quoted context omitted.

How did you do it? When I tried to rebuild cargo I got build errors. I'm starting to suspect the only way to run this tool is make a chroot tracking sid or something....

I just followed the installation instructions here: https://doc.rust-lang.org/cargo/getting-started/installation... It'll confirm that you want to install it, because it's already installed I think, and I just selected 1. for Yes.

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

hard pass :)

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