zephyr-0.2.1: README.md
# zephyr
[](http://github.com/coot)
[](https://travis-ci.org/coot/zephyr)
[](https://ci.appveyor.com/project/coot/zephyr)
Experimental tree shaking tool for [PureScript](https://github.com/purescript/purescript).
# Usage
```
# compile your project (or use `pulp build -- -g corefn`)
purs compile -g corefn bower_components/purescript-*/src/**/*.purs src/**/*.purs
# run `zephyr`
zephyr -f Main.main
# bundle your code
webpack
```
or you can bundle with `pulp`:
```
pulp browserify --skip-compile -o dce-output -t app.js
```
You can also specify modules as entry points, which is the same as specifying
all exported identifiers.
`zephyr` reads corefn json representation from `output` directory, removes non
transitive dependencies of entry points and dumps common js modules (or corefn
representation) to `dce-output` directory.
# Zephyr eval
Zephyr can evaluate some literal expressions.
```purescript
import Config (isProduction)
a = if isProduction
then "api/prod/"
else "api/dev/"
```
will be transformed to
```
a = "api/prod/"
```
whenever `isProduction` is `true`. This allows you to have different
development and production environment while still ship a minified code in your
production environment. You may define `isProduction` in a module under
a `src-prod` directory and include it when compiling production code with `pulp
build -I src-prod` and to have another copy for your development environment
under `src-dev` where `isProduction` is set to `false`.
# Build & Test
To build just run `stack build` (or with `nix` `stack --nix build`). If you
want to run test `stack --nix test` is the prefered method, `stack test` will
also work, unless you don't have one of the dependencies: `git`, `node`, `npm`
and `bower`.
# Comments
The `-f` switch is not 100% safe. When on `zephyr` will remove exports from
foreign modules that seems to be not used: are not used in purescript code and
seem not to be used in the foreign module. If you simply assign to `exports`
using javascript dot notation then you will be fine, but if you use square
notation `exports[var]` in a dynamic way (i.e. var is a true variable rather
than a string literal) then `zephyr` might remove code that shouldn't be
removed.
It is good to run `webpack` or `rollup` to run a javascript tree shaking
algorithm on the javascript code that is pulled in your bundle by your by your
foreign imports.