Test/Compile Not Finding Lib/Jar with Scala 3: The Fix You’ve Been Waiting For

Are you stuck in the quagmire of Scala 3, unable to get your tests to compile or run because it can’t find the libraries it needs? Fear not, dear reader, for we’ve been there too! In this article, we’ll explore the reasons behind this issue, and provide you with step-by-step solutions to get you back on track.

The Problem: Test/Compile Not Finding Lib/Jar with Scala 3

So, you’ve upgraded to Scala 3, and suddenly your tests won’t compile or run. You’ve checked your build files, your dependencies, and even your Scala version, but nothing seems to work. You’re not alone! This issue is more common than you think, and it’s not because of Scala 3 itself, but rather how it interacts with your build tool and dependencies.

Why Scala 3 is Different

Scala 3 introduces several changes that can affect how your project compiles and runs. One of the main culprits is the new scala3 compiler, which is designed to be more type-safe and efficient. However, this new compiler can be more finicky when it comes to dependencies and libraries.

Another issue is the way Scala 3 handles implicit conversions. In Scala 2.13, implicit conversions were allowed by default, but in Scala 3, they need to be explicitly enabled. This can cause issues with libraries that rely on implicit conversions.

Solution 1: Check Your Build File

The first step in solving this issue is to check your build file. Whether you’re using sbt, Maven, or another build tool, make sure you’ve updated your Scala version to 3.x. Here’s an example of what your build.sbt file might look like:

scalaVersion := "3.1.2"

libraryDependencies += "org.seleniumhq.selenium" % "selenium-java" % "4.0.0-alpha-6"

Notice the scalaVersion is set to 3.1.2, and the library dependency is specified correctly. If you’re using Maven, your pom.xml file should look similar:

<properties>
    <scala.version>3.1.2</scala.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.seleniumhq.selenium</groupId>
        <artifactId>selenium-java</artifactId>
        <version>4.0.0-alpha-6</version>
    </dependency>
</dependencies>

Solution 1.1: Enable Implicit Conversions

If you’re using Scala 3, you’ll need to enable implicit conversions explicitly. You can do this by adding the following line to your build.sbt file:

scalacOptions += "-language:implicitConversions"

This will allow implicit conversions to work as expected.

Solution 2: Check Your Library Dependencies

Another common issue is that your library dependencies might not be compatible with Scala 3. Check your library versions and make sure they’re compatible with Scala 3. You can do this by checking the library’s documentation or by using a tool like sbt-dependency-graph.

Here’s an example of how you can use sbt-dependency-graph to check your dependencies:

sbt dependency-graph

This will generate a graph of your dependencies, showing you which libraries are compatible with Scala 3 and which ones aren’t.

Solution 2.1: Update Your Libraries

If you find that some of your libraries aren’t compatible with Scala 3, you’ll need to update them to a version that is. You can do this by checking the library’s documentation or by using a tool like Maven Repository.

For example, if you’re using Selenium, you might need to update to a version like 4.0.0-alpha-6, which is compatible with Scala 3:

libraryDependencies += "org.seleniumhq.selenium" % "selenium-java" % "4.0.0-alpha-6"

Solution 3: Check Your Classpath

Sometimes, the issue isn’t with your build file or your library dependencies, but rather with your classpath. Make sure your classpath is set correctly, and that it includes the necessary libraries.

You can check your classpath by running the following command:

sbt show classpath

This will display your classpath, showing you which libraries are included and which ones aren’t.

Solution 3.1: Set Your Classpath Manually

If you find that your classpath isn’t set correctly, you can set it manually by adding the following line to your build.sbt file:

classpath := Seq(file("lib/"))

This will include the lib/ directory in your classpath, which should include your necessary libraries.

Solution 4: Check Your Scala Version

Sometimes, the issue isn’t with your build file, library dependencies, or classpath, but rather with your Scala version itself. Make sure you’re using the correct Scala version, and that it’s compatible with your libraries.

You can check your Scala version by running the following command:

sbt scalaVersion

This will display your Scala version, showing you which version you’re currently using.

Solution 4.1: Downgrade to Scala 2.13

If you find that Scala 3 is causing issues, you can always downgrade to Scala 2.13, which is more stable and widely supported. To do this, simply change your scalaVersion to 2.13:

scalaVersion := "2.13.6"

This should solve the issue, but keep in mind that you might be missing out on the new features and improvements of Scala 3.

Conclusion

In this article, we’ve covered the common issues that can cause test/compile to fail when using Scala 3. We’ve shown you how to check your build file, library dependencies, classpath, and Scala version to identify and solve the problem.

Remember, Scala 3 is a new and evolving language, and it might take some time to get used to its new features and quirks. But with patience and practice, you’ll be able to overcome any obstacle and write efficient, concise, and powerful code.

Solution	Description
Check Build File	Make sure your build file is updated to Scala 3 and includes the necessary libraries.
Enable Implicit Conversions	Add the -language:implicitConversions flag to your build file to enable implicit conversions.
Check Library Dependencies	Make sure your library dependencies are compatible with Scala 3 and update them if necessary.
Check Classpath	Make sure your classpath is set correctly and includes the necessary libraries.
Check Scala Version	Make sure you’re using the correct Scala version and that it’s compatible with your libraries.

By following these solutions, you should be able to overcome the test/compile issue and get your Scala 3 project up and running smoothly. Happy coding!

• Related Articles:
• Scala 3 Release Notes
• What’s New in Scala 3
• IntelliJ Scala Plugin

Did you find this article helpful? Share your thoughts and comments below!

Frequently Asked Question

Get answers to your most pressing Scala 3 conundrums!