4 August 2019

Development Workflow with Clojure CLI tools

clojure-cli logo

Continuing our exploration with Clojure CLI tools, we will discuss what what templates are available to help us create project, Then we will create a new ClojureScript project using figwheel-main and show the different builds we can use to provide several workflows for developing, testing and deploying an application.

We will create a new project using the figwheel-main template, explaining that we need to specify organisation/project-name or organisation.project-name for the clj-new templates to work properly.

Then run the project using the -A:fig:build alias to run with rebel readline to our user account version of deps.edn so it is available for all projects. Then we will run a test runner and see the auto-testing monitoring. Finally we will show ways to configure a deploy workflow that we can use with GitHub

This article is also covered in Practicalli Clojure study group #38 video

Please see earlier articles in this series for background:

Creating projects from templates

In previous articles we have seen that we can use clj-new to create projects using a number of templates. This tool works with most Leiningen and Boot projects, however, it does not provide a deps.edn configuration file if the template itself does not. It should be easy enough to create your own from the project configuration file that is created by a Leiningen or Boot template (depending on how complex the template is).

Create a new project using the figwheel-main template

Using the figwheel-main template we can create a new figwheel-main project with the comand:

clojure -A:new figwheel-main hello-world.core -- --reagent

This creates a basic project with several aliases defined in the deps.edn file for the project

{:deps {org.clojure/clojure {:mvn/version "1.10.0"}
        org.clojure/clojurescript {:mvn/version "1.10.339"}
        reagent {:mvn/version "0.8.1"}}
 :paths ["src" "resources"]
 :aliases {:fig {:extra-deps
                  {com.bhauman/rebel-readline-cljs {:mvn/version "0.1.4"}
                   com.bhauman/figwheel-main {:mvn/version "0.1.9"}}
                 :extra-paths ["target" "test"]}
           :build {:main-opts ["-m" "figwheel.main" "-b" "dev" "-r"]}
           :min   {:main-opts ["-m" "figwheel.main" "-O" "advanced" "-bo" "dev"]}
           :test  {:main-opts ["-m" "figwheel.main" "-co" "test.cljs.edn" "-m" practicalli.test-runner]}}}
  • :fig adds the figwheel-main and rebel-readline libraries as dependencies
  • :build runs figwheel-main and creates a build of the project code and tests
  • :min creates a minified single JavaScript file for deployment
  • :test runs all the tests once using the test-runner

We will explore these builds and the workflow they provide as we go through this article.

Running figwheel

We can run figwheel by specifying figwheel-main as the main namespace. Figwheel will run a browser and connect to its JavaScript REPL, sending any code we type there to be evaluated..

clojure -A:fig -m figwheel.main

Running a deps.edn project from CIDER (Emacs/Spacemacs) may require a .dir-locals.el file to set which alias you wish to run by default. CIDER version 0.23 onwards should offer you a choice of alias to run.

The browser will show the default figwheel website that contains basic instructions on how to work with figwheel.

figwheel-main - REPL host page

com.bhauman/rebel-readline-cljs is defined as a dependency in the :fig alias in the project deps.edn. This allows figwheel to detect the presence of rebel readline and use it when starting the ClojureScript REPL, to give a very interactive command line. If rebel readline is dectected you will see the following line a few lines before the cljs.user=> prompt.

[Rebel readline] Type :repl/help for online help info
This confirms that we are using Rebel Readline.

Clojure CLI tools - Figwheel-main - rebel readline

If you type :repl/help command at the prompt, as you type you immediately notice that :repl/help character are syntax highlighted. Upon hitting enter, you will see a useful reference for the REPL’s capabilities displayed.

Figwheel-main - repl help

Use the clojure command when using rebel-readline. The clj command provides it’s own terminal line reader

We can call expressions in the REPL prompt, for example some typical ClojureScript such as (map inc [2 4 6 8])

Or we can evaluate some JavaScript interop code and see things change in the browser (js/alert "Notification from the command line")

Running figwheel and building the project

So far we have only run figwheel, however, our template did create some simple code that we can run that displays a website.

The template also added more aliases that defined different ways to build a project.

When developing we would typically run the :build alias along with :fig

clojure -A:fig:build

Figwheel-main - project - hello world

when we look in the project deps.edn file we can see the details of the command that the build alias uses :build {:main-opts ["-m" "figwheel.main" "-b" "dev" "-r"]}

This configuration is the equivalent of running the command clojure -A:fig -m figwheel.main -b dev -r

This command uses the :fig alias to add figwheel-main and rebel readline libraries, sets figwheel-main as the main namespace, the build as dev and -r to run a REPL.

Running tests once

The source code for tests are placed under the top level test directory and uses a directory path that matches their namespace, matching those in src. Source code files test a matching namespace and have -test added to the end of their name. For example, if we have a source namespace of practicalli.hello-world, the tests would be in practicalli.hello-world-test.

We can run tests created by the figwheel-main template by running clojure with the :test alias.

As before, the :fig alias pulls in the figwheel-main and rebel-readline dependencies.

clojure -A:fig:test

This will open a browser and connect to its JavaScript REPL and run the tests. The results can be seen in the terminal window from where you ran the clojure command.

Figwheel-main - test output in terminal

The :test alias sets figwheel.main as the main namespace so it can run the figwheel test-runner functions

:test {:main-opts ["-m" "figwheel.main" "-co" "test.cljs.edn" "-m" practicalli.test-runner]}

Continuous testing

Running a figwheel-main build will also include continuous testing service, so you can instantly see the results of your tests.

clojure -A:fig:build

http://localhost:9500/figwheel-extra-main/auto-testing will show the live results of running the tests.

Figwheel-main - tests - auto-testing webpage results

You may see the auto-testing host page display before showing the tests

Figwheel-main - tests - auto-testng host page

Packaging up a single compiled artifact for production

The building of ClojureScript applications generates lots of files under target/public, as this is the most efficient way to manage changes to your application during development. Using only a single file when deploying your application to the live system makes your application website faster to load (only one http request).

The ClojureScript compiler has four :optimizations modes :none, :whitespace, :simple and :advanced.

The figwheel-main template provides a :min alias to generate a single minified file that has been run through the Google Closure compiler to eliminate any uncalled code. This generates a single file called target/public/cljs-out/dev-main.js

You can manually copy this file to a suitable deployment directory when you publish your application live.

Deploying to GitHub pages

GitHub pages provides a fast and free service for running a website (html, css and JavaScript files). You can run a website by placing all the files in a docs directory.

Rather than manually copy the dev-main.js file each time you want to deploy, create a new build configuration to output the single JavaScript file to a different location.

Create a file called github-pages.cljs.edn to represent a new build and add the following configuration

{:main practicalli.hello-world
 :output-to "docs/cljs-out/dev-main.js"}

Then edit the deps.edn file and change the :min alias to use the deploy build

:min {:main-opts ["-m" "figwheel.main" "-O" "advanced" "-bo" "github-pages"]}

Instead of changing the :min alias, you could also add a new alias to deploy to GitHub pages directory.

:github-pages {:main-opts ["-m" "figwheel.main" "-O" "advanced" "-bo" "github-pages"]}

See package a single file for production for more details.


It is very easy to add aliases and build configurations to customise the workflows you use for your Clojure CLI tools project. As all the configuration files are in EDN, they are Clojure maps and therefore very easy to work with and understand.

There are more examples of options for figwheel-main projects on the https://figwheel.org/ website.

Thank you. @jr0cket

Tags: clojure-cli tools-deps figwheel-main