How to use the command `scala-cli` (with examples)

This article showcases various use cases of the scala-cli command, which is a tool for interacting with the Scala programming language.

Use case 1: Start a REPL (interactive shell) using a specific Scala and JVM version

Code:

scala-cli --scala 3.1.0 --jvm temurin:17

Motivation:

Starting a REPL (Read-Eval-Print Loop) with a specific Scala and JVM version allows developers to experiment and test their code in an interactive environment. It can be helpful when trying out new features or libraries offered by a particular version of Scala.

Explanation:

• --scala: Specifies the version of Scala to be used in the REPL.
• --jvm: Specifies the version of the JVM (Java Virtual Machine) to be used in the REPL.

Example output:

The scala-cli command will start an interactive shell (REPL) using Scala version 3.1.0 and JVM version temurin:17.

Use case 2: Compile and run a Scala script

Code:

scala-cli run path/to/script.scala

Motivation:

Compiling and running a Scala script allows developers to quickly execute standalone Scala code without the need to create a full-fledged project. It is useful for writing and testing small scripts, utilities, or experiments.

Explanation:

• run: Instructs scala-cli to compile and run the provided Scala script.
• path/to/script.scala: Specifies the path to the Scala script to be executed.

Example output:

The scala-cli command will compile and run the Scala script located at the specified path. The output will be the result of executing the script.

Use case 3: Compile and test a Scala script

Code:

scala-cli test path/to/script.scala

Motivation:

Testing is an essential part of software development. With scala-cli, you can conveniently compile and test Scala scripts, ensuring that they produce the expected results and meet the desired specifications.

Explanation:

• test: Instructs scala-cli to compile and test the provided Scala script.
• path/to/script.scala: Specifies the path to the Scala script to be tested.

Example output:

The scala-cli command will compile and execute the test cases defined in the Scala script located at the specified path. The output will display the test results, indicating whether the tests passed or failed.

Use case 4: Format a Scala script, updating the file in-place

Code:

scala-cli fmt path/to/script.scala

Motivation:

Code formatting is crucial for maintaining readable and consistent codebases. By using the scala-cli fmt command, developers can automatically format Scala scripts according to the specified style guide, enhancing code readability and maintainability.

Explanation:

• fmt: Instructs scala-cli to format the provided Scala script.
• path/to/script.scala: Specifies the path to the Scala script to be formatted.

Example output:

The scala-cli command will format the Scala script located at the specified path, updating it in-place. The output will not include any specific output message unless there is an error during the formatting process.

Use case 5: Generate files for IDE (VSCode and IntelliJ) support

Code:

scala-cli setup-ide path/to/script.scala

Motivation:

IDE (Integrated Development Environment) support is crucial for efficient and productive programming. By using the scala-cli setup-ide command, developers can generate the necessary files for enabling IDE support in popular Scala IDEs like VSCode and IntelliJ IDEA.

Explanation:

• setup-ide: Instructs scala-cli to generate IDE support files.
• path/to/script.scala: Specifies the path to the Scala script for which IDE support files are required.

Example output:

The scala-cli command will generate the necessary files (e.g., project metadata, build configuration, library dependencies) at the specified path, ensuring that Scala IDEs like VSCode and IntelliJ IDEA can provide comprehensive language features, code suggestions, and error highlighting for the Scala script.

Conclusion:

The scala-cli command provides a range of useful functionalities for working with the Scala programming language. From starting a REPL with specific Scala and JVM versions to compiling, testing, formatting Scala scripts, and generating IDE support files, scala-cli simplifies various aspects of Scala development. By understanding and utilizing the different use cases, Scala developers can enhance their productivity and code quality.