Bundle Cabal and Cabal-syntax source with cabal-install?

[mpickering]

Perhaps we should bundle the latest Cabal and Cabal-syntax libraries with the cabal-install executable data files.

Then cabal-install can decide whether to build the latest Cabal library on the fly if the user's plan requires a `very new cabal version.

For example #9632 would benefit from this, if you use --multi-repl you get a constraint on a very new Caball library.

Some care would need to be taken to engineer things so that the new version is not picked as a matter of priority and only if explicitly needed.

My intuition is that if the packages were provided as a local+noindex repo then things would work out "just right".

I constructed an incomplete POC here (not currently using local+noindex): https://github.com/mpickering/cabal/tree/wip/bundle-cabal-package

Is this desirable to keep working on?

[michaelpj]

Adding a complicated and unprecedented (nobody else does something like this, right?) path that can only be triggered in unusual circumstances seems like a recipe for trouble, IMO.

[fgaz]

To me it doesn't seem worth the trouble, since normal releases are not affected

[gbaz]

The issue only seems to arise when using pre-release versions of cabal, no? In such cases, I think its fine that they are not fully feature-complete until release, or that we require user making use of them require a custom repo.

I do think that a custom remote repo url for the bleeding edge of Cabal would be nice to provide, to facilitate pre-release testing, and this should be straightforward to add to existing github infrastructure?

We could then document this as a suggested cabal.project for people are testing pre-releases.

[andreabedini]

👎 cabal-install already supports building a specific version of Cabal for a package custom-setup. Using source-repository-package to include Cabal's master is the correct solution I think.

edit: does source-repository-package add an available version or overrides the package? 🤔

[philderbeast]

edit: does source-repository-package add an available version or overrides the package? 🤔

I didn't check whether a source-repository-package could override a local package (I wouldn't expect it could) but I did check to see if a source-repository-package could refer to its own repository locally.

git diff
diff --git a/cabal.project b/cabal.project
index d506fe9b1..4773934a0 100644
--- a/cabal.project
+++ b/cabal.project
@@ -1,6 +1,11 @@
 import: cabal.project.latest-ghc
 
-packages: Cabal/
+source-repository-package
+  type: git
+  location: .
+  branch: master
+  subdir: Cabal
+
 packages: cabal-testsuite/
 packages: Cabal-syntax/
 packages: cabal-install/

$ cabal build all --dry-run
Warning: this is a debug build of cabal-install with assertions enabled.
fatal: repository '.' does not exist

$ git status
On branch master
Your branch is up to date with 'origin/master'.

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
	modified:   cabal.project

[philderbeast]

I tried a little harder with location to satisfy git;

• location: file:///home/<username>/<some-path>/cabal/.git

$ cabal build all --dry-run
Warning: this is a debug build of cabal-install with assertions enabled.
Cloning into '/home/.../cabal/dist-newstyle/src/-f8fda6deb0823b0d'...
remote: Enumerating objects: 129882, done.
remote: Counting objects: 100% (129882/129882), done.
remote: Compressing objects: 100% (41924/41924), done.
remote: Total 129882 (delta 86260), reused 125375 (delta 82459), pack-reused 0
Receiving objects: 100% (129882/129882), 45.50 MiB | 65.07 MiB/s, done.
Resolving deltas: 100% (86260/86260), done.
HEAD is now at 9025af597 Merge pull request #9683 from mpickering/wip/package-db-fix
Resolving dependencies...
Build profile: -w ghc-9.8.2 -O1
In order, the following would be built (use -v for more details):
 - Cabal-3.10.2.1 (lib) (requires build)
...

• location: file:///./.git

$ cabal build all --dry-run
Warning: this is a debug build of cabal-install with assertions enabled.
Cloning into '/home/philderbeast/dev/src/cabalism/cabal/dist-newstyle/src/-9789c1b843441545'...
fatal: '/./.git' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

• location: file:///../cabal/.git

$ cabal build all --dry-run
Warning: this is a debug build of cabal-install with assertions enabled.
Cloning into '/home/philderbeast/dev/src/cabalism/cabal/dist-newstyle/src/-a64f0eadcf6723c2'...
fatal: '/../cabal/.git' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

[andreabedini]

@philderbeast that's interesting but what is the problem you are trying to solve? Why using source-repository-package rather than packages? I think I miss some context.

[philderbeast]

@andreabedini I don't have a problem with source-repository-package but your question (that I quoted) prompted me to try something to know if that was possible and to tread on the edge of what is possible.

[andreabedini]

@andreabedini I don't have a problem with source-repository-package but your question (that I quoted) prompted me to try something to know if that was possible and to tread on the edge of what is possible.

That quote was indeed the context I had missed <3 thank you