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We define `ServerT (NamedRoutes api) m` as `api (AsServerT m)`, so that the server of an record-defined API is a record of handlers. The implementation piggy backs on the instance for “vanilla” servant types with `(:<|>)`, using the `GServantProduct` for converting backd and forth between the record / vanilla servers. The main difficulty is that GHC needs to know that this operation is legit, which can be expressed as the fact that: ``` GToServant (Rep (ServerT (NamedRoutes api))) m ~ ServerT (GToServant (Rep (api AsApi))) m ``` plus a few additional constraints. This is easy enough for `route`, as we know that `m ~ Handler`. But in the case of `hoistServerWithContext`, the two involved monads are unknown ; in other words, this constraint needs to hold `forall m.` Switching `-XQuantifiedConstraints` on is not sufficient, as our constraints involve type families (`Rep` and `ServerT`). Our trick is to use an intermediary typeclass, `GServer`, as a provider of evidence (in the form of a `Dict`) that our constraints are indeed satisfied for a particular monad. The only instance of `GServer` is defined along with it, so it is practically invisible to users. |
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| .github | ||
| changelog.d | ||
| doc | ||
| nix | ||
| servant | ||
| servant-auth | ||
| servant-client | ||
| servant-client-core | ||
| servant-client-ghcjs | ||
| servant-conduit | ||
| servant-docs | ||
| servant-foreign | ||
| servant-http-streams | ||
| servant-machines | ||
| servant-pipes | ||
| servant-server | ||
| .gitignore | ||
| .stylish-haskell.yaml | ||
| cabal.ghcjs.project | ||
| cabal.project | ||
| CONTRIBUTING.md | ||
| default.nix | ||
| ghcjs.nix | ||
| hlint.yaml | ||
| README.md | ||
| servant.png | ||
| setup.py | ||
| sources.txt | ||
| stack-ghcjs.yaml | ||
| stack.yaml | ||
| stack.yaml.lock | ||
| streaming-benchmark.sh | ||
servant - A Type-Level Web DSL
Getting Started
We have a tutorial that introduces the core features of servant. After this article, you should be able to write your first servant webservices, learning the rest from the haddocks' examples.
The core documentation can be found here. Other blog posts, videos and slides can be found on the website.
If you need help, drop by the IRC channel (#haskell-servant on libera.chat) or mailing list.
Contributing
See CONTRIBUTING.md
Release process outline (by phadej)
- Update changelog and bump versions in
mastergit log --oneline v0.12.. | grep 'Merge pull request'is a good starting point (use correct previous release tag)
- Create a release branch, e.g.
release-0.13- Release branch is useful for backporting fixes from
master
- Release branch is useful for backporting fixes from
- Smoke test in
servant-universegit submodule foreach git checkout masterandgit submodule foreach git pullto get newest of everything.cabal new-build --enable-tests allto verify that everything builds, andcabal new-test allto run tests- It's a good idea to separate these steps, as tests often pass, if they compile :)
- See
cabal.projectto selectivelyallow-newer - If some packages are broken, on your discretisation there are two options:
- Fix them and make PRs: it's a good idea to test against older
servantversion too. - Temporarily comment out broken package
- Fix them and make PRs: it's a good idea to test against older
- If you make a commit for
servant-universe, you can use it as submodule in private projects to test even more
- When ripples are cleared out:
git tag -sthe releasegit push --tagscabal sdistandcabal upload
TechEmpower framework benchmarks
We develop and maintain the servant TFB entry in https://github.com/haskell-servant/FrameworkBenchmarks/
To verify (i.e. compile and test that it works)
./tfb --mode verify --test servant servant-beam servant-psql-simple --type json plaintext db fortune
To compare with warp
./tfb --mode benchmark --test warp servant servant-beam servant-psql-simple --type json plaintext db fortune
To compare with reitit (Clojure framework)
./tfb --mode benchmark --test reitit reitit-async reitit-jdbc servant servant-beam servant-psql-simple --type json plaintext db fortune
You can see the visualised results at https://www.techempower.com/benchmarks/#section=test
Nix
A developer shell.nix file is provided in the nix directory
See nix/README.md