Test all supported bazel versions in integration tests

[k1nkreet]

This PR is an invitation to discuss which Bazel versions we are considering as supported, since we can explicitly specify all Bazel versions which would be tested on CI.
As a start I've added all major versions from the interval specified in haskell/private/versions.bzl

The second question is which nixpkgs Bazel versions we are going to test. Current implementation offers to specify a list of Nixpkgs packages to test, but it will use nixpkgs version pinned in rules_haskell/nixpkgs/default.nix (there is no bazel_5 package for ex.) which is a bit unfair to rules_haskell's users. As a suggestion maybe we should use pair (nixpkgs revision, bazel package) to identify bazel packages to test. Or just keeping rules_haskell/nixpkgs/default.nix up-to-date will be good enough?

[aherrmann]

As a start I've added all major versions from the interval specified in haskell/private/versions.bzl

IIUC, this corresponds to all minor versions in the range.
According to Bazel's versioning policy

• A major release contains features that are not backward compatible with the previous release.
• A minor release contains new backward-compatible features.

Perhaps a lower and upper bound for each major version would be enough? E.g. if we start relying on a new minor release feature, we may no longer be compatible with a previous minor of the same major release family.

[k1nkreet]

Perhaps a lower and upper bound for each major version would be enough? E.g. if we start relying on a new minor release feature, we may no longer be compatible with a previous minor of the same major release family.

Agreed

[aherrmann]

Looks like CI is unhappy about something.

[k1nkreet]

Should we test Bazel 5.x also? @aherrmann what do you think?

[aherrmann]

Should we test Bazel 5.x also? @aherrmann what do you think?

Yes, though, feel free to do that in a separate PR if it needs fixing some compatibility issues.

[aherrmann]

IIUC these version numbers are duplicated between bazel_versions.bzl and haskell/private/versions.bzl. Is there a good reason for that? Otherwise, can this be avoided?

[k1nkreet]

Whoops, the point was to deduplicate that, I just forgot to remove bazel_versions.bzl :)

[aherrmann]

Nice, thank you!