纯 java 项目，使用 scalatest 编写的单元测试存在编译器兼容性问题

Question

我们有一个简单的 java 项目，其单元测试用 scalatest 编写：

• 没有 scala 库编译 scope ( autoScalaLibrary:= false )
• scala-compiler 添加到测试 scope 以使用 scalatest 编译用 scala 编写的单元测试
• scala-library, scalatest 添加到测试 scope 用于单元测试

从 intellij 以及命令行 sbt 控制台执行单元测试时出现以下错误：-

scalac: error while loading package, class file '/Users/loc/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.8/scala-library-2.13.8.jar(scala/reflect/package.class)' is broken
(class java.lang.RuntimeException/error reading Scala signature of package.class: Scala signature package has wrong version
 expected: 5.0
 found: 5.2 in package.class)

下面是简化的 build.sbt 文件：-

name := "pure-java-project-with-scala-tests"

//this is added for packaging
enablePlugins(PackPlugin)

//this will not add scala library to compile classpath, as our project is a pure java project
//this will also not add scala library when "sbt pack" is triggered
autoScalaLibrary := false
//this will disable cross-building, as our project is a pure java project
crossPaths := false

//this will add scalatest to test classpath, as our project unit tests will be written using scalatest
libraryDependencies += "org.scalatest" %% "scalatest" % "3.2.10" % Test
//this will add scala library classes to test classpath, as our project unit tests will be written using scalatest
libraryDependencies += "org.scala-lang" % "scala-library" % "2.13.8" % Test

//our assumption is scala-compiler, it is required to compile scala unit tests
//but it is giving below error, when I try to execute unit test from intellij as well as sbt
libraryDependencies += "org.scala-lang" % "scala-compiler" % "2.13.8" % Test

简化项目可以在https://github.com/moglideveloper/pure-java-project-with-scala-tests找到

sbt gitter 链接：- https://gitter.im/sbt/sbt?at=61e30f06f5a3947800088f3d

Answer 1

由于您没有为项目定义Scala版本，因此当您执行%%以包含ScalaTest时，它使用默认的sbt 版本，即2.12 ，从而导致二进制不兼容。

我相信最好的解决方案是使用scalaVersion:= "2.13.8定义项目的正确Scala版本并删除其显式依赖项。