26 July 2019

Gaining confidence with Clojure CLI tools

clojure-cli logo

We are going to try out the different command line options available as we continue our journey into the Clojure CLI tools..

We explore the different ways to running Clojure code, from a single expression to a full project. We include examples of aliases for optional configuration and combining aliases to create specific configurations when running a project. Finally we will see how to diagnose a project and understand potential sources of conflicts.

Newer content can be found in Using Clojure tools section of Practicalli Clojure

Please see earlier articles in thise series for background:

CLI options - getting help

clojure -h, -? or --help lists the options are available for the Clojure CLI tool. You should see output as follows:

clojure --help
Usage: clojure [dep-opt*] [init-opt*] [main-opt] [arg*]
       clj     [dep-opt*] [init-opt*] [main-opt] [arg*]

The clojure script is a runner for Clojure. clj is a wrapper
for interactive repl use. These scripts ultimately construct and
invoke a command-line of the form:

java [java-opt*] -cp classpath clojure.main [init-opt*] [main-opt] [arg*]

The dep-opts are used to build the java-opts and classpath:
 -Jopt          Pass opt through in java_opts, ex: -J-Xmx512m
 -Oalias...     Concatenated jvm option aliases, ex: -O:mem
 -Ralias...     Concatenated resolve-deps aliases, ex: -R:bench:1.9
 -Calias...     Concatenated make-classpath aliases, ex: -C:dev
 -Malias...     Concatenated main option aliases, ex: -M:test
 -Aalias...     Concatenated aliases of any kind, ex: -A:dev:mem
 -Sdeps EDN     Deps data to use as the last deps file to be merged
 -Spath         Compute classpath and echo to stdout only
 -Scp CP        Do NOT compute or cache classpath, use this one instead
 -Srepro        Ignore the ~/.clojure/deps.edn config file
 -Sforce        Force recomputation of the classpath (don't use the cache)
 -Spom          Generate (or update existing) pom.xml with deps and paths
 -Stree         Print dependency tree
 -Sresolve-tags Resolve git coordinate tags to shas and update deps.edn
 -Sverbose      Print important path info to console
 -Sdescribe     Print environment and command parsing info as data

 -i, --init path     Load a file or resource
 -e, --eval string   Eval exprs in string; print non-nil values
         --report target     Report uncaught exception to "file" (default), "stderr", or "none",
                             overrides System property clojure.main.report

 -m, --main ns-name  Call the -main function from namespace w/args
 -r, --repl          Run a repl
 path                Run a script from a file or resource
  • Run a script from standard input -h, -?, --help Print this help message and exit For more info, see: https://clojure.org/guides/deps_and_cli https://clojure.org/reference/repl_and_main

Running code - the REPL

clojure --repl or clojure -r runs a repl, so you can create your application right there in the command line terminal.

clojure --repl

Clojure 1.10.1

This seems to be the same as the default behaviour when running clojure

Running Code - just an expression

We can just evaluate a Clojure expression using the --eval string or -e option. This option takes the expression as a string, so dont forget those double quotes.

clojure -e "(+ 1 2 3)"


Calling code this way will print non-nil values. So if we have an expression that returns nil as a side effect, then that value will not be printed.

clojure -e "(println (+ 1 2 3))"


And if an expression only returns nil, then nothing is printed

clojure -e "(if (= 1 2) true nil)"

Running code - from a project

We saw in the Practicalli study group that you can run a project just by specifying the main namepsace.

Using the project practicalli/first-cli-app we can Run the project using the command:

clojure -m practicalli.first-app

The command called the -main function defined in practicalli.first-app namespce (src/practicalli/first_app.clj)

-Aalias - include configuration sections when running clojure

Use aliases to define additional configuration sections that will be pulled into the overall configuration, as you call clojure on the command line.

From the ### Combining Aliases

As this is Clojure practicalli/first-cli-app we have two aliases defined, `:We have already been combining configurations and so its not surprising that we can combine aliases

{:paths ["resources" "src"]

 :deps {org.clojure/clojure {:mvn/version "RELEASE"}}

 :aliases {:test {:extra-paths ["test"]
                  :extra-deps {org.clojure/test.check {:mvn/version "RELEASE"}}}

           :runner {:extra-deps
                      {:git/url "https://github.com/cognitect-labs/test-runner"
                       :sha "76568540e7f40268ad2b646110f237a60295fa3c"}}
                    :main-opts ["-m" "cognitect.test-runner" "-d" "test"]}}}

clojure -A:test will add test to the search path and include the org.clojure/test.check library.

clojure -A:runner will add the com.congnitect/test-runner library from GitHub and then run with the cognitect.test-runner as the main namespace. clojure will also include configuration from the test build configuration.

The practicalli/first-cli-app does not yet define a dev build, so no additional configuration is added when using the -A:runner alias.

Combining Aliases

We have already been combining configurations and so its not surprising that we can combine aliases too.

The practicalli/study-group-guide defines several aliases

{: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]}}}

clojure -A:fig will include the library for figwheel-main library and include the :extra-paths of target, where JavaScript is generated and test for project unit tests.

clojure -A:fig:build will do the above and also build the project with figwheel-main, first loading in the dev build configuration.

The dev build is defined in dev.cljs.edn file.

^{:watch-dirs ["test" "src"]
  :css-dirs ["resources/public/css"]
  :auto-testing true}
{:main practicalli.study-group-guide}

-Sdeps - adding dependencies to deps.edn

The -Sdeps option will also add the given dependency to the current projects deps.edn

Create a new project directory called packing-code

Create and edit a file called deps.edn

Add the following simple configuration

Add a dependency to this file using the Clojure CLI tools

clojure -Sdeps '{:deps {pack/pack.alpha {:git/url "https://github.com/juxt/pack.alpha.git" :sha "dccf2134bcf03726a9465d2b9997c42e5cd91bff"}}}' -m mach.pack.alpha.inject 'd9023b24c3d589ba6ebc66c5a25c0826ed28ead5'

The command should execute without error and if so no output is returned. So open the deps.edn file in the project and check the dependency has been added.

It does seem easier to simply edit the deps.edn file and add project dependencies, especially as the code may need formatting. If you are working with a bigger project then using the CLI to add a dependency to an existing deps.edn project configuration could be a convenient way to share new dependencies between teams or others who want to use your project, reducing the risk of copy/paste errors or adding different versions.

It could be useful to create a script that populates a project deps.edn file with all the same depencencies. What happens if you try add the same dependency but with different versions? Maybe using clojure - script-to-set-dependencies.sh

Error: no deps.edn file

if you are not in a project with a deps.edn file then the call to clojure -Sdeps ,,, will fail with the following error

Execution error (FileNotFoundException) at java.io.FileInputStream/open0 (FileInputStream.java:-2).
deps.edn (No such file or directory)

Full report at:

A gist of the complete error if you are interested

-Stree - adding dependencies to deps.edn

clojure -Stree in a project directory will show all the library dependencies you added to the project along with all the depencencies that each of those libraries have.

-Stree is a very useful diagnostic tool when you have clashes between dependencies, or more likely the version of dependencies that the libraries you added as dependences have as dependencies (I think that needs a diagram).

In the practicalli/first-cli-app we can see that the org.clojure/clojure library we added has two libraries as its dependencies.

clojure -Stree

org.clojure/clojure 1.10.1
  org.clojure/spec.alpha 0.2.176
  org.clojure/core.specs.alpha 0.2.44

If we look at practicalli/study-group-guide project which uses Clojure, ClojureScript and reagent libraries, the dependency tree is much larger.

clojure -Stree
org.clojure/clojure 1.10.0
  org.clojure/core.specs.alpha 0.2.44
  org.clojure/spec.alpha 0.2.176
org.clojure/clojurescript 1.10.339
  org.clojure/data.json 0.2.6
  org.clojure/google-closure-library 0.0-20170809-b9c14c6b
    org.clojure/google-closure-library-third-party 0.0-20170809-b9c14c6b
  org.mozilla/rhino 1.7R5
  com.cognitect/transit-clj 0.8.309
    com.cognitect/transit-java 0.8.332
      commons-codec/commons-codec 1.10
      com.fasterxml.jackson.core/jackson-core 2.8.7
      org.msgpack/msgpack 0.6.12
        com.googlecode.json-simple/json-simple 1.1.1
        org.javassist/javassist 3.18.1-GA
  org.clojure/tools.reader 1.3.0-alpha3
  com.google.javascript/closure-compiler-unshaded v20180610
    com.google.errorprone/error_prone_annotations 2.0.18
    com.google.jsinterop/jsinterop-annotations 1.0.0
    com.google.javascript/closure-compiler-externs v20180610
    com.google.guava/guava 22.0
      org.codehaus.mojo/animal-sniffer-annotations 1.14
      com.google.j2objc/j2objc-annotations 1.1
    args4j/args4j 2.33
    com.google.protobuf/protobuf-java 3.0.2
    com.google.code.findbugs/jsr305 3.0.1
    com.google.code.gson/gson 2.7
reagent/reagent 0.8.1
  cljsjs/react-dom 16.3.2-0
  cljsjs/react 16.3.2-0
  cljsjs/react-dom-server 16.3.2-0
  cljsjs/create-react-class y15.6.3-0

Managing dependency clashes

In the figwheel-main project we saw that reagent/reagent library had 4 additional dependencies it relied upon. If one of those dependencies were causing an issue, we could define an exclusion on the reagent/reagent dependency entry

{:deps {org.clojure/clojure {:mvn/version "1.10.0"}
        org.clojure/clojurescript {:mvn/version "1.10.339"}
        reagent {:mvn/version "0.8.1"
                 :exclusions [cljsjs/react-dom

clojure -Stree would now show that reagent/reagent only brings in two additional dependencies.

clojure -Stree

reagent/reagent 0.8.1
  cljsjs/react 16.3.2-0
  cljsjs/create-react-class y15.6.3-0

-Sresolve-tags - adding dependencies to deps.edn

TODO: investigate

-Sverbose - Clojure version and paths before running REPL

clojure -Sverbose simply shows the version of Clojure and all the paths and files used to run the REPL. Then it runs a REPL as normal.

clojure -Sverbose
version      =
install_dir  = /usr/local/lib/clojure
config_dir   = /home/jr0cket/.clojure
config_paths = /usr/local/lib/clojure/deps.edn /home/jr0cket/.clojure/deps.edn deps.edn
cache_dir    = .cpcache
cp_file      = .cpcache/1067532457.cp

Clojure 1.10.1

The config_paths configuration shows which deps.edn files are used to build up the configuration, very useful for debugging missing or incorrect configuration (if its pulling in unexpected files into the configuration).

Read the Development Workflow with Clojure CLI tools article for and example of Clojure CLI tools with a figwheel-main project

-Sdescribe - showing the configuration and where it came from

The -Sdescribe option provides a simple way to understand where clojure is getting its configuration from and what the key parts of that configuration are.

clojure -Sdescribe

{:version ""
 :config-files ["/usr/local/lib/clojure/deps.edn" "/home/jr0cket/.clojure/deps.edn" "deps.edn" ]
 :install-dir "/usr/local/lib/clojure"
 :config-dir "/home/jr0cket/.clojure"
 :cache-dir ".cpcache"
 :force false
 :repro false
 :resolve-aliases ""
 :classpath-aliases ""
 :jvm-aliases ""
 :main-aliases ""
 :all-aliases ""}

Thank you. @practicalli

Tags: clojure-cli tools-deps