daml/Upgrading.md
Andreas Herrmann 0c16823c1b
Upgrade rules_haskell and pin stack_snapshot (#6548)
* Update rules_haskell

* Pin stack_snapshot repositories

* Document stack_snapshot_json

CHANGELOG_BEGIN
CHANGELOG_END

* Don't pin stack_snapshot on Windows

The lock file is generated on Unix and includes unix specific
dependencies, e.g. `unix`. Most developers don't have easy access to a
Windows machine, so regenerating the lock file for Windows would be
inconvenient.

* upgrade stack 2.1.3 --> 2.3.1 on Windows

Co-authored-by: Andreas Herrmann <andreas.herrmann@tweag.io>
2020-07-02 18:55:09 +02:00

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# How to upgrade packages in this repo
## Stackage
The daml repository uses a custom stack snapshot defined in
`stack-snapshot.yaml`. Modify the `resolver` entry in that file to update the
base Stackage snapshot. Update the package overrides defined in that file as
appropriate.
A few Stackage packages require custom patches or custom build rules. These are
defined in the `WORKSPACE` file and referenced in the `vendored_packages`
attribute to `stack_snapshot` in the same file.
After changing any of this entries you need to execute the following command to
update the lock-file:
```
bazel run @stackage-unpinned//:pin
```
## Nixpkgs
To update the nixpkgs revision, find a commit in nixkgs-unstable from
https://github.com/NixOS/nixpkgs-channels/commits/nixpkgs-unstable and
use it in the `rev` field in `nix/nixpkgs/default.src.json`. Set the
`sha256` to a dummy hash, e.g., 64 zeros and run `nix-build -A tools
-A cached nix` and nix will tell you the correct hash.
After upgrading the revision, the easiest solution is usually to open
a PR and see what fails on CI (running the builds locally can take
quite some time). The most common reason for failures is usually that
we have overriden a specific package with certain patches that no
longer work. In that case, a good first step is to check if these
patches are still necessary and if not try to switch to the unpatched
package from nixpkgs.