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servant/GHCJS.md
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1# Support for ghcjs
3This branch of servant implements experimental support for
4[ghcjs](https://github.com/ghcjs/ghcjs) for `servant-client`.
5This means it allows you to write Haskell code in terms of `servant-client`,
6compile it with `ghcjs` to javascript and then use it to execute XHRs from a
7browser. The idea is that this should work transparently for the programmer,
8i.e. from a user's perspective it should work exactly as it does when compiled
9with `ghc`.
11## Status
13This branch is experimental.
15Known caveats:
17- Sending bodies in requests doesn't work when using methods `GET` and `HEAD`.
18 At least when running the test-suite with node. `GET` and `HEAD` requests are
19 not supposed to have request bodies and [xhr2](https://www.npmjs.com/package/xhr2)
20 -- which we use to issue XHRs from node -- discards the request bodies for `GET` and
21 `HEAD` requests. (This might actually work in some browsers, no clue.) This causes one
22 failing test in the test-suite.
23- We don't have CI for running the test-suite with `ghcjs`. We tried to make
24 that work, but failed miserably. That's the main reason why this is not merged
25 to `master`.
26- `servant-client` uses libraries that are not optimized for `ghcjs`. I haven't
27 investigated this much, but I could imagine that e.g. a native javascript JSON
28 parser would be much faster than `aeson` compiled by `ghcjs`.
30## Getting it to work
32The `stack` file that is used to run the test-suite with `ghcjs` may provide
33some inspiration: `servant-client/test/ghcjs/stack-ghcjs.yaml`.
35## Running the tests
37You can run the tests by doing:
39``` bash
40./servant-client/test/ghcjs/run-tests.sh
41```
43## Further development
45I propose to use the branch `client-ghcjs` as a place for further development
46on `ghcjs` support for `servant-client`. We could
48- create PRs against the branch,
49- for releases on `master` merge `master` into this branch to not fall behind,
50- maybe even create tags, e.g. `ghcjs-v0.6` and `ghcjs-v0.7.1` to give people
51 fixed commits to stick to.