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Defining aliasesλ︎

Aliases extend the built-in functionality of Clojure CLI via community libraries and tools, either in a project specific or a user deps.edn configuration file.

Aliases are explicitly added to the clojure command, e.g. clojure -M:repl/rebel to start a repl with rebel rich terminal UI.

Aliases are optional configuration that supports the development workflow.

Aliases can be used to :

  • add libraries and directories to the class path
  • configure how to run community tools and provide default options
Understanding Clojure CLI Execution Options

Understand the execution options (exec-opts) on the command line options ensures an effective use of Clojure CLI tools.

Configuration fileλ︎

deps.edn is an EDN configuration file containing a single hash-map with several top-level keywords. All keywords are optional.

The installation of Clojure CLI contains a configuration

  • adds src and org.clojure/clojure library
  • Maven Central & repository sources.

Configuration available to all projects (or stand-alone tools) is defined in a user deps.edn configuration in either $XDG_CONFIG_HOME/clojure or $HOME/.clojure.

Project specific configuration is defined in a deps.edn file in the root of the Clojure project.

User configuration locations

If XDG_CONFIG_HOME environment variable is set, then the user configuration is $XDG_CONFIG_HOME/clojure/deps.edn

Otherwide the user configuration is $HOME/.clojure/deps.edn.

The CLJ_CONFIG environment variable will be used if set.

Alias keysλ︎

An alias name is a keyword in Clojure, e.g. :test/env, so the : is an intrinsic part of the alias name.

Keys used to define an alias are:

  • :extra-paths - a vector of directory names added to the project class path, e.g. ["env/dev" "env/test"]
  • :extra-deps - a map of additional library dependencies, as a Maven library, Git repository or local directory
  • {domain/library-name {:mvn/version "1.2.33"}} maven library
  • {domain/name {:git/url "" :git/sha 'ab3de67'}}
  • {io.github.account/repository-name {:git/tag "2023-01-10" :git/sha 'ab3de67'}}
  • {}
  • :main-opts - a vector of command line options passed to clojure.main
  • :exec-fn - the fully qualified name of a function to be run by clojure.exec
  • :exec-args - default arguments passed to the function, over-ridden by matching argument keys specified on the command line

Keys used when defining an alias for a standalone tool which exclude the paths and dependencies defined in top-level keys.

  • :replace-paths - use only the paths specified as the class path
  • :replace-deps - use only the libraries specified, defined as a Maven library or Git repository
alias :paths and :deps short-cuts

Using :paths and :deps keys in an alias are short-cuts for their respective replace-paths and :replace-deps keywords

Using :paths and :deps in an alias can be very confusing and Practialli recommends using the explicit names for greater clarity

Clojure CLI -T option

-T execution option will exclude the top-level :paths and :deps keys

-T sets "." as the path, adding only paths and libraries defined in aliases used with the execution flag

clojure.main aliasλ︎

:main-opts specifies the options passed to a clojure.main alias, using the clojure -M execution option flag.

The value is a vector containing individual string values that represent each option, i.e. option flag and value.

-m is used to define the fully qualified namespace in which clojure.main should look for the -main function.

The :main-opts vector defines arguments that are passed to the -main function, the same kind of arguments that would be passed via the command line.

The "--middleware" argument adds cider-nrepl middleware to the nREPL server, allowing Cider and other editors complete control over the REPL. The syntax uses values wrapped in a vector.

The "-interactive" argument runs an interactive REPL prompt. A headless process is run without this option.

  {:extra-deps {nrepl/nrepl                   {:mvn/version "0.9.0"}
                cider/cider-nrepl             {:mvn/version "0.27.4"}}
   :main-opts  ["-m" "nrepl.cmdline"
                "--middleware" "[cider.nrepl/cider-middleware]"

This alias is called using the command clojure -M:repl/cider

clojure.exec aliasλ︎

:exec-fn specifies the fully qualified name of the function, using the clojure -X execution option flag .

:exec-args specifies a hash-map of default key/value pairs passed to the :exec-fn function. The defaults can be overridden on the command line with respective key/value pairs.

Arguments can be nested within the :exec-args map, especially useful on projects with several component configurations (server, database, logging) and managed by a component system (i.e Integrant)

  {:exec-fn practicalli.service/start
   :exec-args {:http/server {:port 8080
                             :join? fale}
               :log/mulog :elastic-search}}}}

To run with the default arguments:

clojure -X:project/run

Over-ride the default arguments by passing them on the command line

clojure -X:project/run '[:http/server :port]' 8888 :log/mulog :console :profile :dev

In this command the vector defines the path to the :port key and over-rides the default value. :log/mulog is a top-level key which changes the log publisher type. :profile is another top-level key that sets the environment to :dev (e.g. to configure Integrant / Aero).

Arguments in a nested map within the alias can be traversed (as with get-in and update-in functions) to override the default values in the alias. So to set a different port value :

Argument keys should either be a top-level key or a vector of keys to refer to a key in a nested hash-map of arguments.

An alias can contain configuration to run both clojure.main and clojure.exec (useful if steadily migrating users from -M to -X approach without breaking the user experience)


Practicalli Clojure CLI Config provides a wide range of aliases

Practicalli Clojure CLI Config is a configuration designed to work across all Clojure projects, containing unique and meaningful alias names for ease of understanding.

Simple Projectλ︎

A new Clojure project can be made by creating a deps.edn file and respective src & test directory trees.

A project deps.edn file typically contains :path, :deps and :aliases sections, although deps.edn could start with a simple {} empty hash-map.

{:paths ["src" "resources"]

 {org.clojure/clojure {:mvn/version "1.11.1"}}

 {:test/env {:extra-paths ["test"]}}}

The test path and associated libraries are added as an alias as they are not required when packaging or running a Clojure application. :path and :deps keys are always included by default, :aliases are optional and only included when specified with the clojure command, e.g. clojure -M:test/env

clojure.main toolλ︎

The Cognitect Lab test runner included the test directory in the class path, so test code will be included when run with this alias.

The test runner dependency is pulled from a specific commit shared on GitHub (defined as a Git SHA).

The main namespace is set to that library and the -main function is called when using this alias.


  {:extra-paths ["test"]
   :extra-deps  {com.cognitect/test-runner
                {:git/url ""
                 :git/sha     "f7ef16dc3b8332b0d77bc0274578ad5270fbfedd"}}
     :main-opts   ["-m" "cognitect.test-runner"]}

Clojure Exec toolλ︎

With Clojure CLI tools version the -X flag was introduced using aliases with Clojure exec.

The configuration should define a fully qualified function that runs the tool.

The function should take arguments as key/value pairs as with an Edn hash-map, rather than relying on positional arguments as strings.

In this example, :exec-fn defines the fully qualified function name that will be called. :exec-args is a hash-map of the default key values pairs that are passed to the function as an argument.

  {:replace-deps {seancorfield/clj-new {:mvn/version "1.1.23"}}
   :main-opts    ["-m" "clj-new.create"]    ;; deprecated
   :exec-fn      clj-new/create
   :exec-args    {:template lib :name practicalli/playground}

Default arguments can be over-ridden in the command, e.g. clojure -X:project/new :template app :name practicalli/simple-application uses a different template

Additional arguments can be sent when running the command, e.g. clojure -X:project/new :template figwheel-main :name practicalli/landing-page :args '["--reagent"]' uses the figwheel-main template, specifies a name and :args arguments sent to

:ns-default can also be used to qualify the function that will be executed in an alias. :ns-default is especially useful when there are several functions that could be called from the specific namespace.

The command line can over-ride the :exec-fn function configuration, allowing for a default configuration that can be easily over-ridden.


  {:replace-deps {seancorfield/clj-new {:mvn/version "1.1.226"}}
   :main-opts    ["-m" "clj-new.create"]    ;; deprecated
   :ns-default   clj-new
   :exec-fn      create
   :exec-args    {:template lib :name practicalli/playground}

Keyword naming

Alias names are a Clojure keyword, which can be qualified to provide context, e.g. :project/create.

Aliases are composable (chained together) and their path and deps configurations merged:

clojure -M:task/path:task/deps:build/options

When multiple aliases contain a :main-opts configurations they are not merged, the configuration in the last alias is used


clj-exec: clj-exec update: Clojure CLI execution options Tips for designing aliases