Wrong indirect reverse dependencies for arithmoi

[Bodigrim]

https://hackage.haskell.org/package/arithmoi-0.13.0.0 says "Reverse Dependencies | 22 direct, 7356 indirect". This does not look right, I'm pretty sure that a transitive closure is well below one hundred packages.

[gbaz]

Good eye. This has to do with how revdeps are calculated on hackage, which we could tune. scientific is listed as a direct revdep, because it depended on arithmoi at circa version 3.0.0 for a while, but it no longer does. So the revdeps of scientific in turn get adduced to the transitive closure, etc.

Arguably we should have some constraint on which version of a package constitutes a "revdep" -- only the most current, perhaps? cc: @ysangkok

[ysangkok]

Note that we already do have a more restrictive listing on https://hackage.haskell.org/package/arithmoi/reverse , where it explicitly filters the revdeps for whether they accept the latest version.

[gbaz]

How did we decide which page would show which, and also how do we provide a link to that second page? I'm not sure if I recall the discussions over the tradeoffs here...

[ysangkok]

I don't think we had a discussion on this. If I remember correctly, the deps that don't accept a specific version are filtered out after getting the closure that is "too large".

The reason that I chose to keep the package package unfiltered is probably because I thought that it would be better to minimize the processing done on the package page. I am not sure whether this choice makes sense, since I haven't actually benchmarked it. I wasn't focusing too much on the UI, since my main goal was to get the rev dep email notifications ready.

As this issue report shows, it is confusing to people when the closure includes old rev deps. The reason it does this might be because a decision was made (before I got involved) to never delete the rev-dep edges. I never really questioned this.

We should think about a new UI for this. I think some decent primitives are already in place. So we should be able to iterate on the UI without too much risk.

I was wondering whether the "drill-down"[0] mode should really be the primary way of interaction, since I personally haven't used this much. Something that would be interesting to see, which we aren't exposing now, are the actual ranges used by the rev deps. That could easily fit in the table as it currently is. But the question again arises of how to pick a version to pull the range from.

There are many edge cases, due to dependencies getting set conditionally and such.

[0]: finding rev-deps, following a link, getting new rev-deps and repeating

[andreasabel]

Anecdotally, I found the numbers given for reverse dependencies so wrong that they are at least useless spam if not harmfully misleading. For instance I was interested in the importance of https://hackage.haskell.org/package/unix-compat which is presented as:

Reverse Dependencies
81 direct, 4219 indirect [details]

Oh wow, I thought, this package is super important, the Haskell ecosystem will collapse impromptu if this package ever gets outdated. 4219 dependencies, this is more than what is captured by stackage (3000 packages).
Clicking on "details" I get a long popup with tons of trash that has accumulated on hackage, like https://hackage.haskell.org/package/bugzilla (requiring base < 4.7!).

So, yes, this isn't useful information. How can we improve it?

1. First, if you publish data, you have to lay open how you came about this data. So, when I click on "details", I want to read there how these numbers "81 direct, 4219 indirect" were computed. Because it is far from obvious what should count as a dependency. Maybe atm it is something like "we ignore all version bounds, assume any condition and any flag setting always to be true (even if logically inconsistent) and treat A as a dependency of B if any version of B mentioned any version of A in any branch of a conditional or flag selection in any cabal file of B published on hackage". This truthful statement, how embarrasing it might be, gives the user an explanation and justification for the data they see.

2. We should strive for information to be relevant. First, I am not at all interested in all the garbage we have on hackage, and what dependency it has on other garbage. Unfortunately, with the death of the hackage matrix we lost a tool that could help us sort away the garbage. But we could at least let the packages that claim themselves that they are garbage be garbage. E.g. bugzilla claims it is garbage by requiring base < 4.7 so we should not toss it to the user.
   In some sense, stackage has some advantage in presenting data such as reverse dependencies because they can start from a curated set of non-garbage packages.

3. Maybe to shrink the rev deps to a sane amount could be to only consider the latest version of a package. This would fit the main philosophy that only one version (the latest) of a package is of most interest and eventually all packages that depend on it will strive to depend on its latest version.

P.S.: "drill-down" this is just good old depth-first graph search, is it?

[phadej]

claims it is garbage by requiring base < 4.7

That is somewhat opinionated take. The <6 packages can be considered as garbage as well. In fact I'd say that bugzilla is less garbage, as at least it's honest about not being updated. I.e. just by looking at bounds it's hard to say anything, and you'd punish packages with correct metadata, which are just not updated.

IMHO, packdeps has useful info, e.g. https://packdeps.haskellers.com/reverse/unix-compat or https://packdeps.haskellers.com/reverse/arithmoi though it includes any usages IIRC (and doesn't list which components use stuff), not only in library components.

[ysangkok]

I think that a first good step might be to

• Make the info pane consistently show the same info as the /reverse page. Hopefully this won't be too much load, I will have to benchmark this.
• Include the range of the dependent package like packdeps.haskellers.com.

I won't work on this for a while though. When I get more free time in two weeks, I will start working more on Hackage, starting with the vouching feature.

When I start on this feature, I plan on making mockups first.

[juhp]

I have to agree with earlier comments: the current results are often really bad.

I thought that acme-everything was also part of the problem? Or was that a wrong hunch?

[ysangkok]

The main problem is just that all versions are mushed together, so if a library at one point had a dependency, it keeps having it forever.

[juhp]

I find it hard to believe that even all package versions can account for the vast number of indirect dependents of many packages.

But if you say so I have to believe it I guess, but some seem impossible to me.
Or maybe I didn't understand what "indirect" means.

[ysangkok]

@juhp Please show me the concrete example, then we can determine whether it is the same issue, or whether there is a separate issue. It sounds like you're not referring to the arithmoi example.

[juhp]

https://hackage.haskell.org/package/http2 [1]

It is exactly the same problem as arithmoi I believe...

I do feel that acme-everything (which has 7533 dependencies) should be filtered out of reverse dependency results anyway.

If one looks on Stackage: only 2 dependents are listed: https://www.stackage.org/nightly-2024-05-04/package/http2-5.0.1/revdeps - just for comparison

[1] I chose http2 because it is apparently the most frequently downloaded package currently, which I suppose it is a counterpoint or actually makes it a potentially bad example.

[juhp]

But I guess it is not that simple or still a mystery to me anyway, I think we would need to look at specific examples to understand what is going on.

I took the example of Biobase which I cannot easily see how it is related to http2.
Perhaps there are better examples: I guess one needs to search recursively to check carefully.
Nevertheless the results still seem a bit suspicious/surprising to me.

Anyway even just restricting to revdeps for latest version of a package or using reverse/ as Janus suggests would be a vast improvement: basically "anything" would be better than the status quo (it is also a bit annoying that it is not possible to link directly to the reverse deps pop-up).

(For bonus points it could close with Escape - nice to dream 😃)

[gbaz]

Biobase -> PrimitiveArray -> DPUtils -> streaming-bytestring -> http-client

note that streaming-bytestring only depended on http-client in the 1.0 version.