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Common tasks abstracted into a library, building on the examples in the official guide.

Having implemented build.clj (using in several of my open source projects I found there was a lot of repetition across them, so I factored out the common functionality into this library.

Use with build.clj

Since it depends on both and Erik Assum's deps-deploy, your :build alias can just be:

  :build {:deps {io.github.seancorfield/build-clj
                 {:git/tag "v0.8.3" :git/sha "7ac1f8d"}}
          :ns-default build}

Your build.clj can start off as follows:

(ns build
  (:require [ :as b]
            [ :as bb]))

(def lib 'myname/mylib)
;; if you want a version of MAJOR.MINOR.COMMITS:
(def version (format "1.0.%s" (b/git-count-revs nil)))

If you don't want deps-deploy -- perhaps your project is only building uberjars or you have some other deployment process for your JAR files (or perhaps you are not building JAR files at all) -- then you can specify a "slim" entry point to build-clj that does not include that dependency:

  :build {:deps {io.github.seancorfield/build-clj
                 {:git/tag "v0.8.3" :git/sha "7ac1f8d"
                  ;; omits deps-deploy dependency:
                  :deps/root "slim"}}
          :ns-default build}

Standalone CLI Usage

While build-clj is intended primarily for use with a build.clj file, you can use it directly from the CLI without a build.clj file for many common operations.

Assuming you have a :build alias as above (with or without :ns-default), you could run commands like this:

# run the tests using default options:
clojure -T:build
# clean the target folder:
clojure -T:build
# build a library JAR:
clojure -T:build :lib myname/mylib :version '"1.0.123"'
# deploy that library to Clojars:
clojure -T:build :lib myname/mylib :version '"1.0.123"'
# build an application uberjar:
clojure -T:build :lib myname/myapp :main

Tasks Provided

The following common build tasks are provided, all taking an options hash map as the single argument and returning that hash map unchanged so you can reliably thread the build tasks. [Several functions in return nil instead]

  • clean -- clean the target directory (wraps delete from,
  • deploy -- deploy to Clojars (wraps deploy from deps-deploy),
  • install -- install the JAR locally (wraps create-basis and install from,
  • jar -- build the (library) JAR and pom.xml files (wraps create-basis, write-pom, copy-dir, and jar from,
  • uber -- build the (application) uber JAR, with optional pom.xml file creation and/or AOT compilation (wraps create-basis, write-pom, copy-dir, compile-clj, and uber from,
  • run-tests -- run the project's tests (wraps create-basis, java-command, and process from, to run the :main-opts in your :test alias).

For deploy, install, and jar, you must provide at least :lib and :version. For uber, you must provide at least :lib or :uber-file for the name of the JAR file. Everything else has "sane" defaults, but can be overridden.

Note: you can always get help for a build.clj file by running clojure -A:deps -T:build help/doc which uses the help/doc function from the built-in :deps alias in the root deps.edn file.

Typical build.clj with build-clj

You might typically have the following tasks in your build.clj:

(defn ci "Run the CI pipeline of tests (and build the JAR)." [opts]
  (-> opts
      (assoc :lib lib :version version)

(defn install "Install the JAR locally." [opts]
  (-> opts
      (assoc :lib lib :version version)

(defn deploy "Deploy the JAR to Clojars." [opts]
  (-> opts
      (assoc :lib lib :version version)

Or if you are working with an application, you might have:

(defn ci "Run the CI pipeline of tests (and build the uberjar)." [opts]
  (-> opts
      (assoc :lib lib :main main)

Note: this uber task in build-clj supplies the log4j2 conflict handler to the underlying uber task of so that you don't have to worry about the plugins cache files being merged.

pom.xml and jar

By default, the jar task calls's write-pom function and will write pom.xml into target/classes/META-INF/maven/<group>/<artifact>/pom.xml. You can provide a template for that file, that contains information that write-pom does not provide (and does not offer options to override), such as <description> and <licenses>. Whilst that file could be called pom.xml and would get picked up automatically by write-pom as the source POM, that would leave you with a potentially incomplete and/or outdated file. Instead, consider using template/pom.xml or something similar, and specify :src-pom "template/pom.xml" as an additional option to build-clj's jar task:

(defn ci "Run the CI pipeline of tests (and build the JAR)." [opts]
  (-> opts
      (assoc :lib lib :version version :src-pom "template/pom.xml")

template/pom.xml is suggested rather than, say pom_template.xml at the root, so that GitHub Actions' setup_java still find it and recognizes the repo as being Maven-based for caching purposes (it looks for **/pom.xml).

Running Tests

If you want a run-tests task in your build.clj, independent of the ci task shown above, the following can be added:

(defn run-tests "Run the tests." [opts]
  (-> opts (bb/run-tests)))

By default, the run-tests task will run whatever is in your :test alias but if there is no :main-opts, it assumes Cognitect's test-runner:

  {:extra-paths ["test"]
   :extra-deps {org.clojure/test.check {:mvn/version "1.1.1"}
                {:git/tag "v0.5.0" :git/sha "48c3c67"}}
   :exec-fn cognitect.test-runner.api/test}

The above alias allows for tests to be run directly via:

clojure -X:test

The run-tests task above would run the tests as if the :test alias also contained:

   :main-opts ["-m" "cognitect.test-runner"]

If you want to use a different test runner with build-clj, just provide different dependencies and supply :main-opts:

  ;; a :test alias that specifies the kaocha runner:
  {:extra-paths ["test"]
   :extra-deps {lambdaisland/kaocha {:mvn/version "1.0.887"}}
   :main-opts ["-m" "kaocha.runner"]}

With this :test alias, the run-tests task above would run your tests using Kaocha.

Running Additional Programs

In addition, there is a run-task function that takes an options hash map and a vector of aliases. This runs an arbitrary Clojure main function, determined by those aliases, in a subprocess. run-tests uses this by adding a :test alias and in the absence of any :main-opts behind those aliases, assumes it should run cognitect.test-runner's -main function.

run-task picks up :jvm-opts and :main-opts from the specified aliases and uses them as the :java-args and :main-args respectively in a call to to build the java command to run. By default, it runs clojure.main's -main function with the specified :main-args.

For example, if your deps.edn contains the following alias:

  :eastwood {:extra-deps {jonase/eastwood {:mvn/version "0.5.1"}}
             :main-opts ["-m" "eastwood.lint" "{:source-paths,[\"src\"]}"]}

Then you can define an eastwood task in your build.clj file:

(defn eastwood "Run Eastwood." [opts]
  (-> opts (bb/run-task [:eastwood])))

Or you could just make it part of your ci pipeline without adding that function:

(defn ci "Run the CI pipeline of tests (and build the JAR)." [opts]
  (-> opts
      (assoc :lib lib :version version)
      (bb/run-task [:eastwood])


The following defaults are provided:

  • :target -- "target",
  • :basis -- (b/create-basis {}) -- this is a reproducible basis, i.e., it ignores the user deps.edn file -- if you want your user deps.edn included, you will need to explicitly pass :basis (b/create-basis {:user :standard}) into tasks,
  • :class-dir -- (str target "/classes"),
  • :jar-file -- (format \"%s/%s-%s.jar\" target lib version),
  • :uber-file -- (format \"%s/%s-%s.jar\" target lib version) if :version is provided, else (format \"%s/%s-standalone.jar\" target lib).

As of v0.5.0, the four functions that compute those defaults are exposed for use in your own build.clj files:

  • (default-target) -- return the default for :target,
  • (default-basis) -- return the default for :basis,
  • (default-class-dir) -- return the default for :class-dir; (default-class-dir target) is also available,
  • (default-jar-file lib version) -- return the default for :jar-file or :uber-file; (default-jar-file target lib version) and (default-jar-file version) are also available (the latter defaults :lib to 'application).

For the functions defined in, you can override the high-level defaults as follows:

  • clean
    • :target,
  • deploy
    • Requires: :lib and :version,
    • :target, :class-dir, :jar-file,
  • install
    • Requires: :lib and :version,
    • :target, :class-dir, :basis, :jar-file,
  • jar
    • Requires: :lib and :version,
    • :target, :class-dir, :basis, :resource-dirs, :scm, :src-dirs, :tag (defaults to (str "v" version)), :jar-file,
  • uber
    • Requires: :lib or :uber-file,
    • :target, :class-dir, :basis, :compile-opts, :main, :ns-compile, :resource-dirs, :scm, :src-dirs, :tag (defaults to (str "v" version) if :version provided), :version
  • run-tests
    • :aliases -- for any additional aliases beyond :test which is always added,
    • Also accepts any options that run-task accepts.

See the docstrings of those task functions for more detail on which options they can also accept and which additional defaults they offer.

As noted above, run-task takes an options hash map and a vector of aliases. The following options can be provided to run-task to override the default behavior:

  • :java-opts -- used instead of :jvm-opts from the aliases,
  • :jvm-opts -- used in addition to the :java-opts vector or in addition to :jvm-opts from the aliases,
  • :main -- used instead of 'clojure.main when building the java command to run,
  • :main-args -- used instead of :main-opts from the aliases,
  • :main-opts -- used in addition to the :main-args vector or in addition to :main-opts from the aliases.

Note: if :main-args is not provided and there are no :main-opts in the aliases provided, the default will be ["-m" "cognitect.test-runner"] to ensure that run-tests works by default without needing :main-opts in the :test alias (since it is common to want to start a REPL with clj -A:test).

Monorepos and Library JARs

If you are working in a monorepo, such as the Polylith architecture, and need to build library JAR files from projects that rely on :local/root dependencies to specify other source components, you will generally want to pass :transitive true to the jar task.

Without :transitive true, i.e., by default, the jar task generates a pom.xml from just the dependencies specified directly in the project deps.edn and does not consider dependencies from local source subprojects. In addition, by default jar only copies src and resources from the current project folder.

With :transitive true, the jar task includes direct dependencies from local source subprojects when generating the pom.xml and will also copy all folders found on the classpath -- which is generally all of the src and resources folders from those local source subprojects.

Note: git dependencies look like local source subprojects so they will also be included if you specify :transitive true -- but your pom.xml will not contain those dependencies anyway so users of your library JAR would have a time if git folders are not copied into the JAR!

Projects Using build-clj

You can see how build-clj is used to reduce boilerplate in the build.clj file of the following projects:


Copyright © 2021 Sean Corfield

Distributed under the Apache Software License version 2.0.

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