All you wanted to know about GHCup development.
Main functionality is in
GHCup module. Utility functions are
organised tree-ish in
Anything dealing with ghcup specific directories is in
Download information on where to fetch bindists from is in the appropriate
This is an open variant, similar to plucky or oops and allows us to combine different error types. Maybe it is too much and it's a little bit unergonomic at times. If it really hurts maintenance, it will be removed. It was more of an experiment.
No use of haskell-TLS
I consider haskell-TLS an interesting experiment, but not a battle-tested and peer-reviewed crypto implementation. There is little to no research about what the intricacies of using haskell for low-level crypto are and how vulnerable such binaries are. Instead, we use either curl the binary or wget. There's also an implementation based on OpenSSL bindings, but it isn't enabled by default, since it would complicate shipping static binaries.
Optics instead of lens
They're a little safer (less Monoid weirdness with view) and have better error messages. Consider the following with lens:
> view (_Just . to (++ "abc")) Nothing ""
> view (_Just % to (++ "abc")) Nothing <interactive>:2:1: error: • An_AffineFold cannot be used as A_Getter • In the expression: view (_Just % to (++ "abc")) Nothing In an equation for ‘it’: it = view (_Just % to (++ "abc")) Nothing
StrictData on by default
Kazu Yamamoto explained it in his PR very well. I like to agree with him. The instances where we need non-strict behavior, we annotate it.
Strict is a little more odd as a default, since it depends on how you define your functions as well.
Code style and formatting
Unfortunately, code formatters are semi-broken on this codebase, due to TH and CPP.
Some light suggestions:
- mtl-style preferred
- no overly pointfree style
wherea lot, so the main function body reads like prose
- documentation is part of the code
Adding a new GHC version
- open the latest
- find the latest ghc version (in yaml tree e.g.
ghcupDownloads -> GHC -> 8.10.7)
- copy-paste it
- adjust the version, tags, changelog, source url
- adjust the various bindist urls (make sure to also change the yaml anchors)
cabal run exe:ghcup-gen -- check -f data/metadata/ghcup-<yaml-ver>.yaml
cabal run exe:ghcup-gen -- check-tarballs -f data/metadata/ghcup-<yaml-ver>.yaml -u 'ghc-8\.10\.8'
Adding a new CLI command
An example illustration on how to deal with optparse-applicative can be seen here: https://gitlab.haskell.org/haskell/ghcup-hs/-/commit/c19dd5ee8b2edbaf0336af143f1c75b6f4843e26
- First major refactor included adding cross support. This added
GHCTargetVersion, which includes the target in addition to the version. Most of the
Versionparameters to functions had to be replaced with that and ensured the logic is consistent for cross and non-cross installs.
- This refactor added windows support wrt #130.
The major changes here were switching
hpathlibrary out for
directory(sadly) and introducing a non-unix way of handling processes via the
processlibrary. It also introduced considerable amounts of CPP wrt file handling, installation etc.
Update version in
ghvervariable at the top of the script)
ghcupURLmust only be updated if we change the
GHCupInfotype or the YAML representation of it. The version of the YAML represents the change increments.
ghcUpVeris the current application version, read from
Add ChangeLog entry
Add/fix downloads in
data/metadata), then verify with
ghcup-gen check -f data/metadata/ghcup-<ver>.yamland possibly (example only)
ghcup-gen check-tarballs -f data/metadata/ghcup-<ver>.yaml -u 'ghc-8.10.7'. Generally, new GHC/cabal/stack/hls versions are only added to the latest yaml file. New GHCup versions are added to all (great care must be taken here to not break the parser... e.g. ARM platforms don't parse in all older formats).
Commit and git push with tag. Wait for tests to succeed and release artifacts to build.
Download release artifacts and upload them
downloads.haskell.org/~ghcupalong with checksum files (
sha256sum --tag * > SHA256SUMS && gpg --detach-sign -u <your-email> SHA256SUMS)
Add ghcup release artifacts to ALL yaml files (see point 4.)
Upload the final
data/metadata/ghcup-<ver>.yaml(and a detached GPG sig of it) to
Update the top-level ghcup symlinks at
Post on reddit/discourse/etc. and collect rewards