Could we shorten the solver rejections message?

[philderbeast]

The solver rejections message can be very long with a lot of repetition. Could we shorten it?

• What we have now with cabal-install at 8070ab1

$ cabal build all --enable-tests --enable-benchmarks --dry-run
HEAD is now at 71c2494 Further improvements in parsing attachments.
Resolving dependencies...
Error: [Cabal-7107]
Could not resolve dependencies:
[__0] next goal: pandoc (user goal)
[__0] rejecting: pandoc-3.1.11, pandoc-3.1.10 (constraint from user target
requires ==3.1.9)
[__0] rejecting: pandoc-3.1.9 (constraint from project config
https://stackage.org/lts-21.7/cabal.config requires ==3.0.1)
[__0] rejecting: pandoc-3.1.8, pandoc-3.1.7, pandoc-3.1.6.2, pandoc-3.1.6.1,
pandoc-3.1.6, pandoc-3.1.5, pandoc-3.1.4, pandoc-3.1.3, pandoc-3.1.2,
pandoc-3.1.1, pandoc-3.1, pandoc-3.0.1, pandoc-3.0, pandoc-2.19.2,
pandoc-2.19.1, pandoc-2.19, pandoc-2.18, pandoc-2.17.1.1, pandoc-2.17.1,
pandoc-2.17.0.1, pandoc-2.17, pandoc-2.16.2, pandoc-2.16.1, pandoc-2.16,
pandoc-2.15, pandoc-2.14.2, pandoc-2.14.1, pandoc-2.14.0.3, pandoc-2.14.0.2,
pandoc-2.14.0.1, pandoc-2.14, pandoc-2.13, pandoc-2.12, pandoc-2.11.4,
pandoc-2.11.3.2, pandoc-2.11.3.1, pandoc-2.11.3, pandoc-2.11.2, pandoc-2.11.1.1,
pandoc-2.11.1, pandoc-2.11.0.4, pandoc-2.11.0.2, pandoc-2.11.0.1, pandoc-2.11,
pandoc-2.10.1, pandoc-2.10, pandoc-2.9.2.1, pandoc-2.9.2, pandoc-2.9.1.1,
pandoc-2.9.1, pandoc-2.9, pandoc-2.8.1, pandoc-2.8.0.1, pandoc-2.8,
pandoc-2.7.3, pandoc-2.7.2, pandoc-2.7.1, pandoc-2.7, pandoc-2.6, pandoc-2.5,
pandoc-2.4, pandoc-2.3.1, pandoc-2.3, pandoc-2.2.3.2, pandoc-2.2.3.1,
pandoc-2.2.3, pandoc-2.2.2.1, pandoc-2.2.2, pandoc-2.2.1, pandoc-2.2,
pandoc-2.1.3, pandoc-2.1.2, pandoc-2.1.1, pandoc-2.1, pandoc-2.0.6,
pandoc-2.0.5, pandoc-2.0.4, pandoc-2.0.3, pandoc-2.0.2, pandoc-2.0.1.1,
pandoc-2.0.1, pandoc-2.0.0.1, pandoc-2.0, pandoc-1.19.2.4, pandoc-1.19.2.3,
pandoc-1.19.2.2, pandoc-1.19.2.1, pandoc-1.19.2, pandoc-1.19.1, pandoc-1.19,
pandoc-1.18, pandoc-1.17.2, pandoc-1.17.1, pandoc-1.17.0.3, pandoc-1.17.0.2,
pandoc-1.17.0.1, pandoc-1.17, pandoc-1.16.0.2, pandoc-1.16.0.1, pandoc-1.16,
pandoc-1.15.2.1, pandoc-1.15.2, pandoc-1.15.1.1, pandoc-1.15.1, pandoc-1.15.0.6,
pandoc-1.15.0.5, pandoc-1.15.0.4, pandoc-1.15.0.3, pandoc-1.15.0.2,
pandoc-1.14.1, pandoc-1.13.2.1, pandoc-1.13.2, pandoc-1.13.1, pandoc-1.13.0.1,
pandoc-1.13, pandoc-1.12.4.2, pandoc-1.12.4, pandoc-1.12.3.3, pandoc-1.12.3.2,
pandoc-1.12.3.1, pandoc-1.12.3, pandoc-1.12.2.1, pandoc-1.12.2, pandoc-1.12.1,
pandoc-1.12.0.2, pandoc-1.12.0.1, pandoc-1.12, pandoc-1.11.1, pandoc-1.11,
pandoc-1.10.1, pandoc-1.10.0.5, pandoc-1.10.0.4, pandoc-1.10.0.3,
pandoc-1.10.0.2, pandoc-1.10.0.1, pandoc-1.10, pandoc-1.9.4.5, pandoc-1.9.4.4,
pandoc-1.9.4.3, pandoc-1.9.4.2, pandoc-1.9.4.1, pandoc-1.9.4, pandoc-1.9.3,
pandoc-1.9.2, pandoc-1.9.1.2, pandoc-1.9.1.1, pandoc-1.9.1, pandoc-1.9.0.5,
pandoc-1.9.0.4, pandoc-1.9.0.3, pandoc-1.9.0.2, pandoc-1.9, pandoc-1.8.2.1,
pandoc-1.8.2, pandoc-1.8.1.2, pandoc-1.8.1.1, pandoc-1.8.1, pandoc-1.8.0.3,
pandoc-1.8.0.2, pandoc-1.8.0.1, pandoc-1.8, pandoc-1.6.0.1, pandoc-1.6,
pandoc-1.5.1.1, pandoc-1.5.1, pandoc-1.5.0.1, pandoc-1.5, pandoc-1.4,
pandoc-1.3, pandoc-1.2.1, pandoc-1.2, pandoc-1.1, pandoc-1.0.0.1, pandoc-1.0,
pandoc-0.46, pandoc-0.45, pandoc-0.44, pandoc-0.43, pandoc-0.42, pandoc-0.41,
pandoc-0.4, pandoc-2.11.0.3, pandoc-1.15.0.1, pandoc-1.15, pandoc-1.14.0.4,
pandoc-1.14.0.3, pandoc-1.14.0.2, pandoc-1.14.0.1, pandoc-1.14 (constraint from
user target requires ==3.1.9)
[__0] fail (backjumping, conflict set: pandoc)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: pandoc

• The same rejections but shortened by dropping the common prefix

$ cabal build all --enable-tests --enable-benchmarks --dry-run
Resolving dependencies...
Error: [Cabal-7107]
Could not resolve dependencies:
[__0] next goal: pandoc (user goal)
[__0] rejecting: pandoc; 3.1.11, 3.1.10 (constraint from user target requires
==3.1.9)
[__0] rejecting: pandoc; 3.1.9 (constraint from project config
https://stackage.org/lts-21.7/cabal.config requires ==3.0.1)
[__0] rejecting: pandoc; 3.1.8, 3.1.7, 3.1.6.2, 3.1.6.1, 3.1.6, 3.1.5, 3.1.4,
3.1.3, 3.1.2, 3.1.1, 3.1, 3.0.1, 3.0, 2.19.2, 2.19.1, 2.19, 2.18, 2.17.1.1,
2.17.1, 2.17.0.1, 2.17, 2.16.2, 2.16.1, 2.16, 2.15, 2.14.2, 2.14.1, 2.14.0.3,
2.14.0.2, 2.14.0.1, 2.14, 2.13, 2.12, 2.11.4, 2.11.3.2, 2.11.3.1, 2.11.3,
2.11.2, 2.11.1.1, 2.11.1, 2.11.0.4, 2.11.0.2, 2.11.0.1, 2.11, 2.10.1, 2.10,
2.9.2.1, 2.9.2, 2.9.1.1, 2.9.1, 2.9, 2.8.1, 2.8.0.1, 2.8, 2.7.3, 2.7.2, 2.7.1,
2.7, 2.6, 2.5, 2.4, 2.3.1, 2.3, 2.2.3.2, 2.2.3.1, 2.2.3, 2.2.2.1, 2.2.2, 2.2.1,
2.2, 2.1.3, 2.1.2, 2.1.1, 2.1, 2.0.6, 2.0.5, 2.0.4, 2.0.3, 2.0.2, 2.0.1.1,
2.0.1, 2.0.0.1, 2.0, 1.19.2.4, 1.19.2.3, 1.19.2.2, 1.19.2.1, 1.19.2, 1.19.1,
1.19, 1.18, 1.17.2, 1.17.1, 1.17.0.3, 1.17.0.2, 1.17.0.1, 1.17, 1.16.0.2,
1.16.0.1, 1.16, 1.15.2.1, 1.15.2, 1.15.1.1, 1.15.1, 1.15.0.6, 1.15.0.5,
1.15.0.4, 1.15.0.3, 1.15.0.2, 1.14.1, 1.13.2.1, 1.13.2, 1.13.1, 1.13.0.1, 1.13,
1.12.4.2, 1.12.4, 1.12.3.3, 1.12.3.2, 1.12.3.1, 1.12.3, 1.12.2.1, 1.12.2,
1.12.1, 1.12.0.2, 1.12.0.1, 1.12, 1.11.1, 1.11, 1.10.1, 1.10.0.5, 1.10.0.4,
1.10.0.3, 1.10.0.2, 1.10.0.1, 1.10, 1.9.4.5, 1.9.4.4, 1.9.4.3, 1.9.4.2, 1.9.4.1,
1.9.4, 1.9.3, 1.9.2, 1.9.1.2, 1.9.1.1, 1.9.1, 1.9.0.5, 1.9.0.4, 1.9.0.3,
1.9.0.2, 1.9, 1.8.2.1, 1.8.2, 1.8.1.2, 1.8.1.1, 1.8.1, 1.8.0.3, 1.8.0.2,
1.8.0.1, 1.8, 1.6.0.1, 1.6, 1.5.1.1, 1.5.1, 1.5.0.1, 1.5, 1.4, 1.3, 1.2.1, 1.2,
1.1, 1.0.0.1, 1.0, 0.46, 0.45, 0.44, 0.43, 0.42, 0.41, 0.4, 2.11.0.3, 1.15.0.1,
1.15, 1.14.0.4, 1.14.0.3, 1.14.0.2, 1.14.0.1, 1.14 (constraint from user target
requires ==3.1.9)
[__0] fail (backjumping, conflict set: pandoc)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: pandoc

[ulysses4ever]

Great idea! But as many great ideas, has been suggested before, I think: #8939

[philderbeast]

I checked out the branch for #9541 from @yvan-sraka. It does nearly the same thing but uses two colons instead of a colon and semi-colon and is a +348 -145 line change.

- [__0] rejecting: pandoc: 3.1.8, 3.1.7, 3.1.6.2, 3.1.6.1, 3.1.6, 3.1.5, 3.1.4
+ [__0] rejecting: pandoc; 3.1.8, 3.1.7, 3.1.6.2, 3.1.6.1, 3.1.6, 3.1.5, 3.1.4

[gbaz]

I would prefer going further and attempt to summarize contiguous version ranges, even though this would be more work.

[__0] rejecting: pandoc; 1.14 through 3.1.8

[philderbeast]

@gbaz I had thought of compressing ranges too but wanted to take a small step that in some cases would half the bulk of the output.

[grayjay]

I think that correctly displaying version ranges would be a much larger and more complex change, with more design considerations. I would be very happy to have the incremental change, especially since a similar issue has been open since 2017 without a fix (#4251).