Compile
Scala CLI compiles your code with its compile
command:
object Hello {
def main(args: Array[String]): Unit =
println("Hello")
}
scala-cli compile Hello.scala
Note that most Scala CLI commands automatically compile your code, if necessary.
The compile
command is useful if you'd like to check that your code compiles,
or know of compilation warnings, without running it or packaging it.
The most common compile
options are shown below.
For a full list of options, run scala-cli compile --help
, or check the options linked in the
reference documentation.
Test scopeβ
--test
makes scala-cli
compile main and test scopes:
scala-cli compile --test Hello.scala
Watch modeβ
--watch
makes scala-cli
watch your code for changes, and re-compiles it upon any change:
scala-cli compile --watch Hello.scala
# Compiling project-cef76d561e (1 Scala source)
# Compiled 'project-cef76d561e'
# Watching sources, press Ctrl+C to exit.
# Compiling project-cef76d561e (1 Scala source)
# Compiled 'project-cef76d561e'
# Watching sources, press Ctrl+C to exit.
Scala versionβ
Scala CLI uses the latest stable version of Scala which was tested in scala-cli
(see our list of Supported Scala Versions). You can specify the Scala version you'd like to use with --scala
:
scala-cli compile --scala 2.13.6 Hello.scala
scala-cli
works with all major 2.12.x
, 2.13.x
, and 3.x
Scala versions.
--scala
also accepts "short" Scala versions, such as 2.12
, 2
, or 3
. In this
case, it picks the highest corresponding stable Scala version:
scala-cli compile --scala 2.12 Hello.scala
scala-cli compile --scala 2 Hello.scala
scala-cli compile --scala 3 Hello.scala
Scala Nightliesβ
The nightly builds of Scala compiler are unstable ones which are published on a nightly basis.
To use the latest Scala 2 and Scala 3 nightly builds, pass 2.nightly
and 3.nightly
, respectively.
You can also request the last 2.12.nightly
and 2.13.nightly
versions. 2.13.nightly
is the same as 2.nightly
.
Moreover, passing the 3.{sub binary number}.nightly
format, such as 3.0.nightly
or 3.1.nightly
is accepted, too.
Scala CLI takes care of fetching the nightly builds of Scala 2 and Scala 3 from different repositories, without you having to pass their addresses as input after the --repo
flag.
For compiling with the latest Scala 2 nightly build:
scala-cli Hello.scala -S 2.nightly
For compiling with the latest Scala 3 nightly build:
scala-cli Hello.scala -S 3.nightly
For compiling with an specific nightly build, you have the full version for:
scala-cli Hello.scala -S 2.13.9-bin-4505094
For adding this inside scala files with using directives, use:
//> using scala "2.nightly"
//> using scala "3.nightly"
//> using scala "2.13.9-bin-4505094"
Dependenciesβ
You can add dependencies on the command-line with --dependency
:
scala-cli compile Hello.scala \
--dependency org.scala-lang.modules::scala-parallel-collections:1.0.4
Note that --dependency
is only meant as a convenience. You should favor
adding dependencies in the source files themselves via using
directives.
You can also add simple JAR files β those that donβt have transitive dependencies β as dependencies, with --jar
:
scala-cli compile Hello.scala --jar /path/to/library.jar
See the Dependency management guide for more details.
Scala compiler optionsβ
Most Scala compiler options can be passed as-is to scala-cli
:
scala-cli compile Hello.scala -Xlint:infer-any
# Compiling project_b729aa2200-cef76d561e (1 Scala source)
# [warn] ./Hello.scala:2:11: a type was inferred to be `Any`; this may indicate a programming error.
# [warn] val l = List("a", true, 2, new Object)
# [warn] ^
# Compiled 'project_b729aa2200-cef76d561e'
All scala-cli
options that start with:
-g
-language
-opt
-P
-target
-V
-W
-X
-Y
are assumed to be Scala compiler options.
Scala compiler options can also be passed with -O
:
scala-cli compile Hello.scala -O -deprecation -O -Xlint:infer-any
# [warn] ./Hello.scala:3:7: method x in class Some is deprecated (since 2.12.0): Use .value instead.
# [warn] opt.x
# [warn] ^
-O
accepts both options with the prefixes shown above, and those without such a prefix.
Scala compiler pluginsβ
Use --compiler-plugin
to add compiler plugin dependencies:
scala-cli compile Hello.scala --compiler-plugin org.typelevel:::kind-projector:0.13.2 --scala 2.12.14
Printing a class pathβ
--class-path
makes scala-cli compile
print a class path:
scala-cli compile --class-path Hello.scala
# /work/.scala/project-cef76d561e/classes:~/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.12.14/scala-library-2.12.14.jar:~/Library/Caches/ScalaCli/local-repo/0.1.0/org.virtuslab.scala-cli/runner_2.12/0.0.1-SNAPSHOT/jars/runner_2.12.jar:~/Library/Caches/ScalaCli/local-repo/0.1.0/org.virtuslab.scala-cli/stubs/0.0.1-SNAPSHOT/jars/stubs.jar
This is handy when working with other tools.
For example, you can pass this class path to java -cp
:
java -cp "$(scala-cli compile --class-path Hello.scala)" Hello
# Hello
Note that you should favor the run
command to run your code, rather than running java -cp
.
The class path obtained this way is only meant for scenarios where scala-cli
doesn't offer a more convenient option.