Add MainComponentRegistrar to classpath only when plugins are given. Resolves #302

Author: tschuchortdev

core/src/main/kotlin/com/tschuchort/compiletesting/AbstractKotlinCompilation.kt

@@ -88,6 +88,9 @@ abstract class AbstractKotlinCompilation<A : CommonCompilerArguments> internal c
 
     var languageVersion: String? = null
 
+    /** Use the new experimental K2 compiler */
+    var useK2: Boolean by default { false }
+
     /** Additional string arguments to the Kotlin compiler */
     var kotlincArguments: List<String> = emptyList()
 
@@ -126,6 +129,7 @@ abstract class AbstractKotlinCompilation<A : CommonCompilerArguments> internal c
         args.allWarningsAsErrors = allWarningsAsErrors
         args.reportOutputFiles = reportOutputFiles
         args.reportPerf = reportPerformance
+        args.useK2 = useK2
 
         if (languageVersion != null)
             args.languageVersion = this.languageVersion
@@ -191,7 +195,16 @@ abstract class AbstractKotlinCompilation<A : CommonCompilerArguments> internal c
                 } else {
                     emptyList()
                 }
-            args.pluginClasspaths = (args.pluginClasspaths ?: emptyArray()) + arrayOf(getResourcesPath())
+            args.pluginClasspaths = (args.pluginClasspaths ?: emptyArray()) +
+                    /** The resources path contains the MainComponentRegistrar and MainCommandLineProcessor which will
+                     be found by the Kotlin compiler's service loader. We add it only when the user has actually given
+                     us ComponentRegistrar instances to be loaded by the MainComponentRegistrar because the experimental
+                     K2 compiler doesn't support plugins yet. This way, users of K2 can prevent MainComponentRegistrar
+                     from being loaded and crashing K2 by setting both [compilerPlugins] and [commandLineProcessors] to
+                     the emptyList. */
+                    if (compilerPlugins.isNotEmpty() || commandLineProcessors.isNotEmpty())
+                        arrayOf(getResourcesPath())
+                    else emptyArray()
         }
 
         val compilerMessageCollector = PrintingMessageCollector(

core/src/main/kotlin/com/tschuchort/compiletesting/MainComponentRegistrar.kt

@@ -47,7 +47,7 @@ internal class MainComponentRegistrar : ComponentRegistrar {
     companion object {
         /** This compiler plugin is instantiated by K2JVMCompiler using
          *  a service locator. So we can't just pass parameters to it easily.
-         *  Instead we need to use a thread-local global variable to pass
+         *  Instead, we need to use a thread-local global variable to pass
          *  any parameters that change between compilations
          */
         val threadLocalParameters: ThreadLocal<ThreadLocalParameters> = ThreadLocal()

core/src/test/kotlin/com/tschuchort/compiletesting/KotlinCompilationTests.kt

@@ -904,5 +904,18 @@ class KotlinCompilationTests {
 			}
 	}
 
+	@Test
+	fun `runs the K2 compiler without compiler plugins`() {
+		val result = defaultCompilerConfig().apply {
+			sources = listOf(SourceFile.kotlin("kSource.kt", "class KSource"))
+			compilerPlugins = emptyList()
+			pluginClasspaths = emptyList()
+			useK2 = true
+		}.compile()
+
+		assertThat(result.exitCode).isEqualTo(ExitCode.OK)
+		assertClassLoadable(result, "KSource")
+	}
+
 	class InheritedClass {}
 }