# zephyr
[![Maintainer: coot](https://img.shields.io/badge/maintainer-coot-lightgrey.svg)](http://github.com/coot)
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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
```

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.