servant/GHCJS.md

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2016-05-13 10:11:13 +02:00
# Support for ghcjs
This branch of servant implements experimental support for
[ghcjs](https://github.com/ghcjs/ghcjs) for `servant-client`.
This means it allows you to write Haskell code in terms of `servant-client`,
compile it with `ghcjs` to javascript and then use it to execute XHRs from a
browser. The idea is that this should work transparently for the programmer,
i.e. from a user's perspective it should work exactly as it does when compiled
with `ghc`.
## Status
This branch is experimental.
Known caveats:
- Sending bodies in requests doesn't work when using methods `GET` and `HEAD`.
At least when running the test-suite with node. `GET` and `HEAD` requests are
not supposed to have request bodies and [xhr2](https://www.npmjs.com/package/xhr2)
-- which we use to issue XHRs from node -- discards the request bodies for `GET` and
`HEAD` requests. (This might actually work in some browsers, no clue.) This causes one
failing test in the test-suite.
- We don't have CI for running the test-suite with `ghcjs`. We tried to make
that work, but failed miserably. That's the main reason why this is not merged
to `master`.
- `servant-client` uses libraries that are not optimized for `ghcjs`. I haven't
investigated this much, but I could imagine that e.g. a native javascript JSON
parser would be much faster than `aeson` compiled by `ghcjs`.
## Getting it to work
The `stack` file that is used to run the test-suite with `ghcjs` may provide
some inspiration: `servant-client/test/ghcjs/stack-ghcjs.yaml`.
## Running the tests
You can run the tests by doing:
``` bash
./servant-client/test/ghcjs/run-tests.sh
```
## Further development
I propose to use the branch `client-ghcjs` as a place for further development
on `ghcjs` support for `servant-client`. We could
- create PRs against the branch,
- for releases on `master` merge `master` into this branch to not fall behind,
- maybe even create tags, e.g. `ghcjs-v0.6` and `ghcjs-v0.7.1` to give people
fixed commits to stick to.