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Figwheel Main Configuration Options

This page is a reference for all of the Figwheel configuration options.

You can enter these options in a figwheel-main.edn file that is in the root of your project directory.

Example figwheel-main.edn file:

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

The options can also be entered as metadata in a Figwheel build file in your project’s root directory. The name of a build file has the form [build-id].cljs.edn where [build-id] is an identifier of your choice.

An example dev.cljs.edn build file that supplies figwheel config options.

^{:watch-dirs ["src" "admin-src"]
  :css-dirs ["resources/public/css"]}
{:main example.core}

Any options provided in the metadata of the build file will override the options in the figwheel-main.edn file.

Commonly used options

The options below are listed in order of importance

:watch-dirs

A list of ClojureScript source directories to be watched and compiled on change.

The directories in :watch-dirs are passed to the compiler as source directories. For this reason, any entry in the watch directories must be on the classpath and must point to the root directory of a ClojureScript namespace source tree.

I.E. If your example.core namespace is located at src/cljs/example/core.cljs you cannot use src as an element of :watch-dirs, you must use the path to the root directory of the namespace tree src/cljs.

:watch-dirs ["cljs-src"]

:css-dirs

A list of CSS source directories to be watched and reloaded into the browser.

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

:ring-handler

A symbol or string indicating a ring-handler to embed in the figwheel.repl server. This aids in quickly getting a dev server up and running. If the figwheel server doesn’t meet your needs you can simply start your own server. The figwheel.client will still be able to connect to its websocket endpoint. Default: none

:ring-handler my-project.server/handler

:ring-server-options

All the options to forward to the ring-jetty-adapter/run-jetty function which figwheel.main uses to run its ring server.

All the available options are documented here: https://github.com/ring-clojure/ring/blob/master/ring-jetty-adapter/src/ring/adapter/jetty.clj#L127

This will normally be used to set the :port and :host of the server.

Most uses of these options are considered advanced. If you find yourself using many of these options you problably need to run your own server outside of figwheel.main.

:rebel-readline

By default Figwheel engauges a Rebel readline editor when it starts the ClojureScript REPL in the terminal that it is launched in.

This will only work if you have com.bhauman/rebel-readline-cljs in your dependencies.

More about Rebel readline: https://github.com/bhauman/rebel-readline

Default: true

:rebel-readline false

:pprint-config

When :pprint-config is set to true. The figwheel.main will print the computed config information and will terminate the process. Useful for understanding what figwheel.main adds to your configuration before it compiles your build.

Default: false

:pprint-config true

:open-file-command

A path to an executable shell script that will be passed a file and line information for a particular compilation error or warning.

A script like this would work ie. in ~/bin/myfile-opener

#! /bin/sh
emacsclient -n +$2:$3 $1

Then add this script in your config:

:open-file-command "myfile-opener"

But that’s not the best example because Figwheel handles emacsclient as a special case. So as long as emacsclient is on the shell path you can simply do:

:open-file-command "emacsclient"

and Figwheel will call emacsclient with the correct args.

:figwheel-core

Whether to include the figwheel.core library in the build. This enables hot reloading and client notification of compile time errors. Default: true

:figwheel-core false

:hot-reload-cljs

Whether or not figwheel.core should hot reload compiled ClojureScript. Only has meaning when :figwheel is true. Default: true

:hot-reload-cljs false

:reload-dependents

Whether or not figwheel.core should reload the namespaces that depend on the changed namespaces in addition to the changed namespaces themselves. Only has meaning when :figwheel is true. Default:true

:reload-dependents false

:connect-url

The url that the figwheel REPL client will use to connect back to the server.

This url is actually a template that will be filled in. For example the default :connect-url is:

"ws://[[config-hostname]]:[[server-port]]/figwheel-connect"

The available template variables are:

For the server side:

[[config-hostname]]  the host supplied in :ring-server-options > :host or "localhost"
[[server-hostname]]  the java.InetAddress localhost name - "Bruces-MacBook-Pro.local" on my machine
[[server-ip]]        the java.InetAddress localhost ip interface - normally 192.168.x.x
[[server-port]]      the port supplied in :ring-server-options > :port or the default port 9500

On the client side:

[[client-hostname]]  the js/location.hostname on the client
[[client-port]]      the js/location.port on the client

If the url starts with a Websocket scheme “ws://” a websocket connection will be established. If the url starts with an http scheme “http” an http long polling connection will be established.

:open-url

Either a boolean value false or a string that indicates the url that the figwheel REPL will open in the browser after the source code has been compiled. A false value will disable this behavior.

The string value is actually a template that can provide optional template variables. For example the default :open-url is:

"http://[[server-hostname]]:[[server-port]]"

The available template variables are:

For the server side:

[[server-hostname]]  the host supplied in :ring-server-options > :host or "localhost"
[[server-port]]      the port supplied in :ring-server-options > :port or the default port 9500

:reload-clj-files

Figwheel naively reloads clj and cljc files on the :source-paths. It doesn’t reload clj dependent files like tools.namspace.

Figwheel does note if there is a macro in the changed clj or cljc file and then marks any cljs namespaces that depend on the clj file for recompilation and then notifies the figwheel client that these namespaces have changed.

If you want to disable this behavior:

:reload-clj-files false

Or you can specify which suffixes will cause the reloading

:reload-clj-files #{:clj :cljc}

:log-file

The name of a file to redirect the figwheel.main logging to. This will only take effect when a REPL has been started.

:log-file "figwheel-main.log"

:log-level

The level to set figwheel.main java.util.logger to. Can be one of: :error :info :debug :trace :all :off

:log-level :error

:client-log-level

The log level to set the client side goog.log.Logger to for figwheel.repl and figwheel.core. Can be one of: :severe :warning :info :config :fine :finer :finest

:client-log-level :warning

:log-syntax-error-style

figwheel.main logging prints out compile time syntax errors which includes displaying the erroneous code. Setting :log-syntax-error-style to :concise will cause the logging to not display the erroneous code. Available options: :verbose, :concise Default: :verbose

:log-syntax-error-style :concise

:load-warninged-code

If there are warnings in your code emitted from the compiler, figwheel does not refresh. If you would like Figwheel to load code even if there are warnings generated set this to true. Default: false

:load-warninged-code true

:ansi-color-output

Figwheel makes an effort to provide colorful text output. If you need to prevent ANSI color codes in figwheel output set :ansi-color-output to false. Default: true

:ansi-color-output false

:validate-config

Whether to validate the figwheel-main.edn and build config (i.e.”.cljs.edn”) files. Default: true

:validate-config false

:validate-cli

Whether to validate the figwheel-main command line options Default: true

:validate-cli false

:target-dir

A String that specifies the target directory component of the path where figwheel.main outputs compiled ClojureScript

The default :output-dir is composed of:

[[:target-dir]]/public/cljs-out/[[build-id]]

The default :output-to is composed of:

[[:target-dir]]/public/cljs-out/[[build-id]]-main.js

If you are using the default figwheel.repl server to serve compiled assets, it is very important that the :target-dir be on the classpath.

The default value of :target-dir is “target”

:target-dir "cljs-target"

:launch-node

A boolean that indicates whether you want figwheel to automatically launch Node. Defaults to true.

:inspect-node

A boolean that indicates whether you want figwheel to enable remote inspection by adding “–inspect” when it launches Node. Defaults to true.

:node-command

A String indicating the Node.js executable to launch Node with. Defaults to “node”

:launch-js

Figwheel optionally launches a JavaScript host environment when it starts a REPL or runs a script. You see this behavior when it opens a browser or starts Nodejs. This behavior can be overridden with the :launch-js option.

Can take the name of an executable script on your system and will pass it either the path to the compiled JavaScript (when the target is Nodejs) or the URL to the JavaScript (when the target is the browser).

Script example:

#! /bin/sh
chrome --headless --disable-gpu --repl --remote-debugging-port=9222 $1

If the above script is named headless-chrome-launcher and is on your path, then you would add this to your config:

:launch-js `headless-chrome-launcher`

Can also take a vector that represents a shell command to invoke. The vector can contain the keywords :output-to and :open-url which will be replaced with the the path or the URL to the compiled JavaScript.

Shell command vector example:

:launch-js ["chrome" "--headless" "--repl" "--disable-gpu" :open-url]

The :launch-js option can also take a namespaced symbol representing a function to invoke. The function will be passed a map containing the keys :open-url and :output-to.

Symbol example:

:launch-js user/start-js-environment

and in your user.clj file:

(defn start-js-environment [{:keys [output-to open-url]}]
   (clojure.java.shell/sh "headless-chome" open-url))

The :launch-js option will take precedence over any node configurations like :node-command or :launch-node.

:cljs-devtools

A boolean that indicates whether to include binaryage/devtools into the clojurescript build. Defaults to true when the target is a browser and the :optimizations level is :none, otherwise it is false.

:cljs-devtools false

:helpful-classpaths

A boolean that indicates whether figwheel should try and be helpful by adding classpaths to help you get started, or whether you want to have complete control over classpaths. Advanced users will want to disable this option.

:helpful-classpaths false

:npm

Support for importing webpack bundles.

Experimental feature! This feature may change or be removed entirely. Only available in 0.1.8-SNAPSHOT or higher

This also works best with ClojureScript >= 1.10.339.

Currently takes a map with only one valid key :bundles. The value of the :bundles key must be a map of bundled JavaScript files to the index JavaScript files that they are compiled from.

:npm {:bundles {"dist/index.bundle.js" "src/webpack/index.js"}}

This feature will read an index.js file like:

import React from 'react';
import ReactDom from 'react-dom';
window.React = React;
window.ReactDom = ReactDom;

and will then generate a :foreign-libs entry for it. For example the above index.js would cause the following to be added to your compiler options:

:foreign-libs [{:file "dist/index.bundle.js"
                :provides ["react" "react-dom"]
                :global-exports {react React
                                 react-dom ReactDom}}]

This will set :npm-deps to false if it hasn’t been previously set.

This will set :infer-externs to true if it hasn’t been previously set.

You can learn more about ClojureScript and Webpack here: https://clojurescript.org/guides/webpack

:pre-build-hooks

A collection of symbol or strings that represent Clojure functions to call just before your ClojureScript sources get built.

These functions will be called before every build.

These functions will be passed the current configuration of the system. This is a fairly complex data-structure and contains the :options for the current build among other things.

:pre-build-hooks [user/gen-testfile]

:post-build-hooks

A collection of symbol or strings that represent clojure functions to call just after your ClojureScript sources have been built.

These functions will be called after every build.

These functions will be passed the current configuration of the system. This is a fairly complex data-structure and contains the :options for the current build among other things.

:post-build-hooks [user/gen-alternate-main-js]

:extra-main-files

A map of keyword ids to Clojurescript option maps.

:extra-main-files will output extra main files besides the one that was configured in your ClojureScript options.

For example this will output a dev-main-test.js file for your tests:

::extra-main-files {:tests {:main example.tests.test-runner}}

This file will be created in addition to the dev-main.js file.

The options will be merged with the ClojureScript options for the current build. Keep in mind that this merge supports keywords prefixed with extra- when you want the values of these keys to be merged. If you supply :extra-preloads in the options map they will be concatenated with the existing :preloads. Since Figwheel works by injecting itself into your config with :preloads and :closure-defines it is recommended that you always use :extra-preloads and :extra-closure-defines if you want to change these values.

This extra main will have all the same configured Figwheel options as the main build. In other words, the extra main will connect to the Figwheel REPL and get reloads just like the main build.

This feature will only output the ClojureScript bootstrap file that you will require on your host page, it will not cause any files to be compiled. So you will need to make sure that you have added all the needed source directories to your :watch-dirs and your classpath.

This will only work under :optimizations level :none.

Figwheel provides a default host page for extra mains so that you do not have to configure one. The default host page can be found at /figwheel-extra-main/[id] where id is the id you supplied as a key in the config you passed to the :extra-main-files. For example the config above you would be able to find the :tests main at /figwheel-extra-main/tests. Keep in mind that the id of the app div on the default host page will be app-[id].

If you don’t want to use the default host page you will need to create a your own host page for it. See https://figwheel.org/docs/your_own_page for help.

This feature is perfect for adding cljs-test-display and devcards to your workflow.

Also keep in mind that you can insert extra behavior with :preloads and you can even change the :target to :nodejs if you want to work on a Nodejs app in parallel with your main build.

::extra-main-files {:devcards {:main example.devcards}}

:build-inputs

Build inputs are passed as the first argument to the CLJS compiler.

Build inputs are normally a list of sources (files and directories) for the compiler to compile.

Figwheel attempts to provide build inputs to the ClojureScript compiler based on your current configuration. The logic is roughly: if you are using :optimizations level :none and not only building once, use the :watch-dirs as the build inputs, otherwise use the :main namespace as the build input.

Using the :watch-dirs as a build input has the advantage that Figwheel will watch and compile all the source files in the :watch-dirs even if they are not required in your application yet. This allows Figwheel to provide compiler feedback while you are working on files that are not in your require tree.

When you provide a :build-inputs in your config you will be overriding the default Figwheel behavior and be specifing which specific inputs you want to send to the compiler.

:build-inputs is a collection of:

:auto-testing

Figwheel will automatically discover all the cljs.test based tests that you have defined and will provide an endpoint to display them with cljs-test-display. It will only provide this by default when the tests are present in your watched directories and a build is using :optimizations level :none.

You can find these tests at the /figwheel-extra-main/auto-testing HTTP endpoint on the Figwheel server.

Figwheel will automatically find all the namespaces with tests in them.

You can enable this feature by specifying:

:auto-testing true

You can specify which namespaces to test:

:auto-testing {:namespaces [example.core-tests example.logic-tests]}

You can also disable cljs-test-display with:

:auto-testing {:cljs-test-display false}

Rarely used options

:cljsjs-resources

When you use libraries from http://cljsjs.github.io they sometimes come bundled with static resources (like CSS files) that you would like to be served from the Figwheel server.

If you set :cljsjs-resources to true the Figwheel server will serve the resources with the cljsjs root.

For example: if there is a CSS file in the react-vis jar at cljsjs/react-vis/common/react-vis.inc.css you will be able to access it via the Figwheel server at the path /react-vis/common/react-vis.inc.css.

:cljsjs-resources true

:client-print-to

The figwheel.repl client can direct printed (via pr) output to the REPL and/or the console. :client-print-to is a list of where you want print output directed. The output choices are :console and :repl Default: [:console :repl]

:client-print-to [:console]

:ring-stack

The figwheel server has a notion of a :ring-stack. The :ring-stack is a composition of basic ring-middleware (think sessions) to wrap around a supplied :ring-handler.

The default :ring-stack is a slightly modified ring.middleware.defaults/wrap-defaults

:ring-stack-options

The figwheel.repl server has a notion of a :ring-stack. The :ring-stack is a composition of basic ring-middleware to wrap around a supplied :ring-handler.

The default :ring-stack is a slightly modified ring.middleware.defaults/wrap-defaults.

:ring-stack-options are the options that figwheel.repl supplies to ring.middleware.defaults/wrap-defaults.

The default options are slightly modified from ring.middleware.defaults/site-defaults:

{:params
 {:urlencoded true, :multipart true, :nested true, :keywordize true},
 :cookies true,
 :session
 {:flash true, :cookie-attrs {:http-only true, :same-site :strict}},
 :static {:resources "public"},
 :responses {:content-types true, :default-charset "utf-8"},
 :figwheel.server.ring/dev
 {:figwheel.server.ring/fix-index-mime-type true,
  :figwheel.server.ring/resource-root-index true,
  :figwheel.server.ring/wrap-no-cache true,
  :figwheel.server.ring/cljsjs-resources false,
  :ring.middleware.not-modified/wrap-not-modified true,
  :co.deps.ring-etag-middleware/wrap-file-etag true,
  :ring.middleware.cors/wrap-cors true,
  :ring.middleware.stacktrace/wrap-stacktrace true}}

You can override these options by suppling your own to :ring-stack-options

If these options are changed significantly don’t be suprised if the figwheel server stops behaving correctly :)

:wait-time-ms

The number of milliseconds to wait before issuing reloads. Set this higher to wait longer for changes. This is the interval from when the first file change occurs until we finally issue a reload event.

Default: 50

:wait-time-ms 50

:mode

The :mode indicates the behavior that occurs after a compile. Options: :repl :serve or :build-once

This is mainly intended for use when you are launching figwheel.main from a script.

Normally defaults to :repl

:broadcast-reload

Figwheel broadcasts hot reloads to all clients that have connected since the figwheel process has started. Set :broadcast-reload to false if you want to only send hot-reloads to the client where the REPL eval occurs. Default: true

:broadast-reload false

:broadcast

In the past figwheel would broadcast REPL evaluations to all connected clients and then print the first result received in the REPL. Setting :broadcast to true will give you back this legacy behavior. Default: false

:broadcast true

:repl-eval-timeout

The time (in milliseconds) it takes for the REPL to timeout. Evaluating any given expression in cljs can take some time. The REPL is configured to throw a timeout exception as to not hang forever.

This config option will determine how long the REPL waits for the result of an eval before throwing.

Default: 8000

:repl-eval-timeout 10000 ;;waits for 10 seconds instead of 8

:hawk-options

If you need to watch files with polling instead of FS events. This can be useful for certain docker environments.

:hawk-options {:watcher :polling}