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Figwheel Main

Clojars Project Documentation

Figwheel Main builds your ClojureScript code and hot loads it as you are coding!

Figwheel heads up example

Get a quick idea of what Figwheel does by watching the 6 minute flappy bird demo of figwheel.

Learn even more by watching a 45 minute talk on Figwheel given at ClojureWest 2015.

Read the introductory blog post.

Support Work on Figwheel and other Clojure tools

I contribute a significant amount of time writing tools and libraries for Clojure and ClojureScript. If you enjoy using figwheel, rebel-readline, spell-spec, cljs-test-display or piggieback please consider making a contribution.

Features

Live code reloading

If you write reloadable code figwheel can facilitate automated live interactive programming.

Supports Node.js

Static file server

The inclusion of a static file server allows you to get a decent ClojureScript development environment up and running quickly. For convenience there is a :ring-handler option so you can embed a ring handler into the figwheel server.

Live CSS reloading

Figwheel will reload your CSS live as well.

Live JavaScript reloading

Figwheel can live reload your JavaScript source files.

Heads up display

Figwheel has a non-intrusive heads up display that gives you feedback on how well your project is compiling. By writing a shell script you can click on errors in the heads up display and they will open in your editor!

Descriptive Errors with Code Context

Figwheel provides descriptive compiler errors that point to where the error is in your code. These errors appear in the REPL as well as the heads up display.

Excellent Configuration Error Reporting

It can be quite daunting, when you are configuring a tool for the first time. Figwheel currently offers excellent configuration error reporting that will help you if you happen to misconfigure something.

ClojureScript REPL

When you launch Figwheel it not only starts a live building/reloading process but it also optionally launches a CLJS REPL into your running application. This REPL shares compilation information with the ClojureScript compiler, allowing the REPL to be aware of the code changes as well. The REPL also has some special built-in control functions that allow you to control the auto-building process and execute various build tasks without having to stop and rerun figwheel.main.

Robust connection

Figwheel’s connection is fairly robust. I have experienced figwheel sessions that have lasted for days through multiple OS sleeps.

Message broadcast

Figwheel broadcasts changes to all connected clients. This means you can see code and CSS changes take place in real time on your phone and in your laptop browser simultaneously.

Respects dependencies

Figwheel will not load a file that has not been required. It will also respond well to new requirements and dependency tree changes.

Won’t load code that is generating warnings

If your ClojureScript code is generating compiler warnings Figwheel won’t load it. This, again, is very helpful in keeping the client environment stable. This behavior is optional and can be turned off.

Try Figwheel with Flappy Bird

Via Leiningen

Make sure you have the latest version of leiningen installed.

Clone this repo:

$ git clone https://github.com/bhauman/flappy-bird-demo-new.git

Change into the flappy-bird-demo-new directory and run:

$ lein fig:build

Via Clojure Tools

First we will want to install the clj and clojure command line tools.

Clone this repo:

$ git clone https://github.com/bhauman/flappy-bird-demo-new.git

Change into the flappy-bird-demo-new directory and run:

$ clj -A:build

Get started quickly with the template!

You can get a quick greenfield project with the Figwheel Template

Learning ClojureScript

If you are brand new to ClojureScript it is highly recommended that you do the ClojureScript Quick Start first. If you skip this you will probably suffer.

There is a lot to learn when you are first learning ClojureScript, I recommend that you bite off very small pieces at first. Smaller bites than you would take when learning other languages like JavaScript and Ruby.

Please don’t invest too much time trying to set up a sweet development environment, there is a diverse set of tools that is constantly in flux and it’s very difficult to suss out which ones will actually help you. If you spend a lot of time evaluating all these options it can become very frustrating. If you wait a while, and use simple tools you will have much more fun actually using the language itself.

Read the Tutorial

There is an extensive getting started tutorial I highly reccomend reading it if you are new to Clojure, ClojureScript and or the new Clojure CLI tools.

tutorial-button

Documentation

The documentation a currently a good resource but is still a work in progress.

Getting Help

You can get help at both the ClojureScript Google Group and on the #clojurescript, #figwheel-main and #beginners Clojurians Slack Channels

Quick Usage

This is abbreviated usage documentation intended for experienced Clojure/Script developers. I highly reccomend the tutorial if you are new to Figwheel and ClojureScript.

Clojure CLI Tools

First, make sure you have the Clojure CLI Tools installed.

On Mac OSX with brew:

brew install clojure

Now launch a ClojureScript REPL with:

clj -Sdeps "{:deps {com.bhauman/figwheel-main {:mvn/version \"0.1.9\"}}}}"  -m figwheel.main

This will first compile browser REPL code to a temp directory, and then a browser will open and a cljs.user=> prompt will appear.

From here you can do REPL driven development of ClojureScript.

With Leiningen

You can also use leiningen by adding it to :dependencies in your project.clj and launching it like so:

lein run -m figwheel.main

With Rebel Readline for much better REPL experience

Figwheel main will automatically use rebel-readline-cljs if it is available. So, you can get Rebel Readline behavior by simply adding it to your dependencies.

clojure -Sdeps "{:deps {com.bhauman/figwheel-main {:mvn/version \"0.1.9\"} com.bhauman/rebel-readline-cljs {:mvn/version \"0.1.4\"}}}}"  -m figwheel.main

As of right now using Rebel readline does create some startup overhead (hoping to correct this in the near future), so you may want to choose use it only when you are going to interact at the REPL.

Setting up a build with Tools CLI

Set up a build which will allow you to start a watch/build/reload process on a set of local ClojureScript source files.

If the following doesn’t work for you please see the tutorial.

The following assumes the current working directory is the root directory of your project.

Ensure your deps.edn file has the figwheel.main dependencies:

{:deps {com.bhauman/figwheel-main {:mvn/version "0.1.9"}
        com.bhauman/rebel-readline-cljs {:mvn/version "0.1.4"}}
 ;; setup some development paths
 :paths ["src" "target" "resources"]
 ;; setup a helpful alias to start the build
 :aliases {:build-dev {:main-opts ["-m" "figwheel.main" "-b" "dev" "-r"]}}}

Create a dev.cljs.edn build file:

{:main example.core}

In src/example/core.cljs, place the following ClojureScript code:

(ns example.core)

(enable-console-print!)

(prn "hello world!")

Then run the command:

clojure -m figwheel.main -b dev -r

This will launch a REPL and start autobuilding and reloading the src directory so that any files you add or change in that directory will automatically be hot reloaded into the browser.

The -b dev or --build dev flag option is indicating that Figwheel should read dev.cljs.edn for build configuration.

The -r or --repl flag indicates that a REPL should be launched.

Interesting to note that the above command is equivalent to:

clojure -m figwheel.main -co dev.cljs.edn -c -r

You can also start your build running with the build-dev alias we defined in the deps.edn to save some typing:

clojure -A:build-dev

Setting up a build with Leiningen

Set up a build which will allow you to start a watch/build/reload process on a set of local ClojureScript source files.

If the following doesn’t work for you please see the tutorial.

The following assumes the current working directory is the root directory of your project.

Ensure your project.clj file has figwheel.main dependencies:

:dependencies [[com.bhauman/figwheel-main "0.1.9"]
               [com.bhauman/rebel-readline-cljs "0.1.4"]]
 ;; setup target as a resource path
:resource-paths ["target" "resources"]
;; set up an alias to invoke your figwheel build
:aliases {"fig" ["trampoline" "run" "-m" "figwheel.main"]
          "build-dev" ["trampoline" "run" "-m" "figwheel.main" "-b" "dev" "-r"]}

Create a dev.cljs.edn build file:

{:main example.core}

In src/example/core.cljs, place the following ClojureScript code:

(ns example.core)

(enable-console-print!)

(prn "hello world!")

Then run the command:

lein trampoline run -m figwheel.main -- -b dev -r

This will launch a REPL and start autobuilding and reloading the src directory so that any files you add or change in that directory will automatically be hot reloaded into the browser.

The -b dev or --build dev flag option is indicating that Figwheel should read dev.cljs.edn for build configuration.

The -r or --repl flag indicates that a REPL should be launched.

using the aliases

We are probably better off using the helpful aliases that we created in the project.clj

You can invoke the above command using the fig alias like so:

lein fig -- -b dev -r

You can also just use the build-dev alias to get the same result:

lein build-dev

Why use an alias here? Why not use a lein plugin? The first reason I’m not using a plugin here is that Leiningen boots a lot faster when it doesn’t have to dynamically load/compile plugin code. Another reason is that figwheel.main’s command line options are much more expressive than lein-figwheel’s and lein aliases are better positioned to leverage that expressiveness.

Using your own HTML to host your app

If would prefer to use your own HTML page to host your application instead of the default page served by figwheel.main, you will first need to ensure that you have added resources to the :paths key in deps.edn, as demonstrated above. After that, you can place the index.html in resources/public/index.html so that it will mask the one served by the figwheel.main helper application.

The following is some example HTML to help you get started. The trickly part is the path to the ClojureScript bootstrap file. The default output path is available at cljs-out/[build-id]-main.js. So in this case it will be: cljs-out/dev-main.js

<!DOCTYPE html>
<html>
  <head>
  </head>
  <body>
    <div id="app"></div>
    <script src="cljs-out/dev-main.js"></script>
  </body>
</html>

You can place CSS and other static assets in the resources/public directory.

Configuring Figwheel Main

If you need to configure figwheel.main, you will use a figwheel-main.edn file in the root of your project directory.

For example let’s explicitly set our watch directory.

Create a figwheel-main.edn file in the root of your project folder with these contents:

{:watch-dirs ["cljs-src"]
 :css-dirs ["resources/public/css"]}

:watch-dirs instructs figwheel.main to watch and compile the sources in the cljs-src directory.

:css-dirs instructs figwheel.main to watch and reload the CSS files in the resources/public/css directory.

If you need to override some of the figwheel configuration options for a particular build, simply add those options as metadata on the build edn.

For example if you want to have :watch-dirs that are specific to the dev build then in your dev.cljs.edn file:

^{:watch-dirs ["cljs-src" "dev"]}
{:main example.core}

All the available configuration options are documented here: https://github.com/bhauman/figwheel-main/blob/master/doc/figwheel-main-options.md

All the available configuration options specs are here: https://github.com/bhauman/figwheel-main/blob/master/src/figwheel/main/schema/config.clj

Classpaths, Classpaths, Classpaths

Understanding of the Java Classpath can be very helpful when working with ClojureScript.

ClojureScript searches for source files on the Classpath. When you add a re-frame dependency like so:

{:deps {com.bhauman/figwheel-main {:mvn/version "0.1.9"}
        com.bhauman/rebel-readline-cljs {:mvn/version "0.1.4"}
        ;; adding re-frame
        re-frame {:mvn/version "1.10.5"}}
 :paths ["src" "target" "resources"]}

The source files in re-frame are on the Classpath and the ClojureScript compiler can find re-frame.core when you require it.

Your sources will need to be on the Classpath so that the Compiler can find them. For example, if you have a file cljs-src/example/core.cljs you should add cljs-src to the :paths key so that the ClojureScript compiler can find your example.core namespace. It is important to note that the src directory is on your Classpath by default.

In Figwheel, the embedded HTTP server serves its files from the Java Classpath.

It actually serves any file it finds on the Classpath in a public sub-directory. This is why we added target and resources to the :paths key in the deps.edn file above. With target and resources both on the Classpath the server will be able to serve anyfile in target/public and resources/public.

The compiler by default compiles artifacts to target for easy cleaning.

It is custmary to put your index.html, CSS files, and other web artifacts in the resources/public directory.

Live CSS Reloading

As mentioned above you configure figwheel.main to live reload your CSS files as you edit them.

Just add a :css-dirs key that lists the CSS directories to watch in your figwheel configuration.

For example in your figwheel-main.edn file:

{:css-dirs ["resources/public"]}

Using CSS Precompilers

Using SASS or LESS and still want to have the benefits of live CSS reloading?

Simply run your sass or less watcher/compiler on the command line and make sure the final output CSS files land in one of the directories that you have listed in your :css-dirs configuration option (mentioned above).

Working with Node.js

Unlike cljs.main, with figwheel.main you will not specify a --repl-env node because the figwheel.repl handles Node.js REPL connections in addition to others.

You can launch a Node REPL like so:

clojure -m figwheel.main -t node -r

You can quickly get a hot reloading CLJS node build up an running using the deps.edn, example.core and dev.cljs.edn above. Simply add a --target node or -t node to the compile command.

clojure -m figwheel.main -t node -b dev -r

This will launch a CLJS Node REPL initialized with example.core you can now edit example/core.cljs and it will be hot reloaded.

Of course if you add :target :nodejs to dev.cljs.edn like so:

{:main example.core
 :target :nodejs}

You be able to run the build more simply:

clojure -m figwheel.main -b dev -r

Reload hooks

It is common to want to provide callbacks to do some housekeeping before or after a hot reload has occurred.

You can conveniently configure hot reload callbacks at runtime with metadata. You can see and example of providing callbacks below:

;; first notify figwheel that this ns has callback defined in it
(ns ^:figwheel-hooks example.core)

;; mark the hook functions with ^:before-load and ^:after-load 
;; metadata

(defn ^:before-load my-before-reload-callback []
    (println "BEFORE reload!!!"))

(defn ^:after-load my-after-reload-callback []
    (println "AFTER reload!!!"))

The reload hooks will be called before and after every hot code reload.

Quick way to understand the command line options

If you supply a -pc or --pprint-config flag to figwheel.main, it will not execute the command. It will instead print out the computed configuration.

For example:

clojure -m figwheel.main -pc -b dev -r

Will output:

---------------------- Figwheel options ----------------------
{:ring-server-options {:port 9550},
 :client-print-to [:repl :console],
 :pprint-config true,
 :watch-dirs ("src"),
 :mode :repl}
---------------------- Compiler options ----------------------
{:main exproj.core,
 :preloads [figwheel.core figwheel.main figwheel.repl.preload],
 :output-to "target/public/cljs-out/dev-main.js",
 :output-dir "target/public/cljs-out/dev",
 :asset-path "cljs-out/dev",
 :aot-cache false,
 :closure-defines
 #:figwheel.repl{connect-url
                 "ws://localhost:9550/figwheel-connect?fwprocess=c8712b&fwbuild=dev",
                 print-output "repl,console"}}

Using figwheel.main from a script

See the figwheel.main/start function and the figwheel.main/start-join functions.

Contributing to the Helper App

Figwheel main comes with a helper Ring app that is served when there is no other html page to host the REPL JavaScript env.

If you are interested in contributing to this app:

First hit me up in the #figwheel-main channel on the clojurians Slack so that we can co-ordinate a bit.

To work on the helper app:

Checkout this repository and change directory to the figwheel-main directory where this README is located.

Then the command

clj -m figwheel.main -b helper -r 

should launch a live development workflow for the Helper application.

tweaking the CSS

The CSS files for the helper app are located at helper-resources/public/com/bhauman/figwheel/helper/css and you should be able to edit them live.

working on the app itself

Both the server-side and client side code are located in src/figwheel/main/helper.cljc and you should be able to work on them live.

If you change the behavior of the CLJS in src/figwheel/main/helper.cljc it will not be reflected in the actual helper app until you compile with make helper

editing helper content

The helper app content is generated from the Markdown files in the helper-content directory. You must compile the markdown with make helper-docs this currently requires ruby and kramdown (gem install kramdown)

keep it simple

The helper app is intended to be very simple in structure. We do not want to add more dependencies and slow the startup time of figwheel.main, and we also do not want to do anything that will interfere with the users running code.

License

Copyright © 2018 Bruce Hauman

Distributed under the Eclipse Public License either version 1.0 or any later version.