Gerrit support for structural diff (difftastic)

[Paul Jolly]

difftastic is a structural diff that understands syntax:

https://github.com/wilfred/difftastic

I would like to understand whether it would be possible for structural diff (via difftastic) support to be added to Gerrit.

I understand ~nothing about the internals of Gerrit, but did get the following response on Twitter:

https://twitter.com/andybons/status/1569646980560715779

Is there a way in which gerrit could shell out to difftastic for diff results?

Starting this discussion in any case in the hope that others are interested in adding structural diff (via difftastic) as a solution in Gerrit!

Thanks

[Martin Fick]

On 9/29/22 11:07 PM, Paul Jolly wrote:
> difftastic is a structural diff that understands syntax:
>
> https://github.com/wilfred/difftastic
>
> I would like to understand whether it would be possible for structural
> diff (via difftastic) support to be added to Gerrit.

Gerrit core implementations are in Java and difftastic is Rust, so this
is not something that would be implemented in core. It would be possible
to make the diff algorithm in core pluggable, and then someone could
potentially provide a diffstatic implementation. This would be quite a
challenge also because Gerrit doesn't perform diffs directly on files,
it operates on git blobs via the jgit APIs, so likely any other diff
implementation would also need some translation layer to work with jgit.
I think this is quite a challenge, for a result that does not likely
align well with most Gerrit maintainer's objectives, so it would take a
fairly motivated other individual/team to make this happen,

-Martin

[Han-Wen Nienhuys]

to add to that: JGit supports multiple diff algorithms; conceivably you could add a structural diff algorithm to JGit. However, JGit is pure Java and is conservative with its dependencies. You'd likely have to reimplement difftastic in Java to start with.

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[Paul Jolly]

>> Gerrit core implementations are in Java and difftastic is Rust, so this
>> is not something that would be implemented in core.

...

> to add to that: JGit supports multiple diff algorithms; conceivably you could add a structural diff algorithm to JGit. However, JGit is pure Java and is conservative with its dependencies. You'd likely have to reimplement difftastic in Java to start with.

Thanks very much for your responses!