WIP: Change diff crate

[vincentdephily]

This explores a fix for #94.

There are two replacement crates in this PR, but it only makes sense to merge one. Neither crate can be used as an exact replacement of the unmaintained crate, because the diffing algorithms don't match : the calculated "distance" is different and there is no way to configure a "split character".

Nevertheless, I used the two crates to showcase two possibilities:

• dissimilar retains the same API; programs will compile with only a function name change, but if they used to configure a split or a distance, the results may be different.
• similar ignores API stability, and exposes more features (even more could be exposed if we wanted)

Both crates have their own feature flag, and I resisted bikeshedding the name of the constructors.

IMHO the second one is more tempting, except if we want to avoid tying ourselves into a particular diffing crate and want to to the most common denominator features.

We could make a release that deprecates the difference feature and adds the similar feature, or we could make an immediate replacement (simplifying the bikeshedding and cosing the rustsec advisory faster).

TODO:

• Choose a path (this is my first PR here, so I won't dare)
• Update changelog and docs
• Change default feature
• Remove a diff crate or two
• Any other similar feature we want to expose ?

[vincentdephily]

Looks like easy CI fixes, I'll do that during the week.

Interestingly, looks like pretty-assertions selected diff as a replacement after looking at similar. For some reason I hadn't looked at diff, not sure if it's any better for our usecase.

[asomers]

Which predicates are changing exactly? Is it just similar or are there others too? I would say that you should do what you have to, and I'll note it in Mockall's CHANGELOG .

[epage]

Which predicates are changing exactly? Is it just similar or are there others too? I would say that you should do what you have to, and I'll note it in Mockall's CHANGELOG .

We might be changing the settings for the `DifferencePredicate which is created via predicates::str::similar. This would require a major version bump for predicates (but not predicates-core where the Traits live) and any crate that re-exports predicates would need to do similar.

If we do a breaking change, my question is if we need either of these functions (choose the split, allow edit distance besides 0)

[vincentdephily]

We might be changing the settings for the DifferencePredicate which is created via predicates::str::similar.

Also, even if we keep the .distance() API intact, the measured distance value will no longer be the same. So if a user has a test with a fine-tuned distance value, it's likely no longer correct and implies a major version bump too.

[epage]

Thanks again for all of this research. I've pulled it together in #107. I ended up using a different crate just because another of my crates was using it. We can always swap out and add features as there is demand.