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GHCJS.md

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+# 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.