Check correct file extension in SourceFile factory functions

Author: tschuchortdev

src/main/kotlin/com/tschuchort/compiletesting/KotlinCompilation.kt

@@ -437,8 +437,8 @@ class KotlinCompilation {
 				)
 		)
 
-		val kotlinSources = sourceFiles.filter(File::isKotlinFile)
-		val javaSources = sourceFiles.filter(File::isJavaFile)
+		val kotlinSources = sourceFiles.filter(File::hasKotlinFileExtension)
+		val javaSources = sourceFiles.filter(File::hasJavaFileExtension)
 
 		val sourcePaths = mutableListOf<File>().apply {
 			addAll(javaSources)
@@ -513,7 +513,7 @@ class KotlinCompilation {
 				kaptSourceDir.listFilesRecursively()
 
 		// if no Kotlin sources are available, skip the compileKotlin step
-		if(sources.filter<File>(File::isKotlinFile).isEmpty())
+		if(sources.filter<File>(File::hasKotlinFileExtension).isEmpty())
 			return ExitCode.OK
 
 		// in this step also include source files generated by kapt in the previous step
@@ -563,7 +563,7 @@ class KotlinCompilation {
 	/** Performs the 4th compilation step to compile Java source files */
 	private fun compileJava(sourceFiles: List<File>): ExitCode {
 		val javaSources = (sourceFiles + kaptSourceDir.listFilesRecursively())
-			    .filterNot<File>(File::isKotlinFile)
+			    .filterNot<File>(File::hasKotlinFileExtension)
 
 		if(javaSources.isEmpty())
 			return ExitCode.OK

src/main/kotlin/com/tschuchort/compiletesting/SourceFile.kt

@@ -16,6 +16,7 @@ abstract class SourceFile {
          * Create a new Java source file for the compilation when the compilation is run
          */
         fun java(name: String, @Language("java") contents: String, trimIndent: Boolean = true): SourceFile {
+            require(File(name).hasJavaFileExtension())
             val finalContents = if (trimIndent) contents.trimIndent() else contents
             return new(name, finalContents)
         }
@@ -24,6 +25,7 @@ abstract class SourceFile {
          * Create a new Kotlin source file for the compilation when the compilation is run
          */
         fun kotlin(name: String, @Language("kotlin") contents: String, trimIndent: Boolean = true): SourceFile {
+            require(File(name).hasKotlinFileExtension())
             val finalContents = if (trimIndent) contents.trimIndent() else contents
             return new(name, finalContents)
         }

src/main/kotlin/com/tschuchort/compiletesting/Utils.kt

@@ -51,9 +51,9 @@ internal fun Path.listFilesRecursively(): List<Path> {
     return files
 }
 
-internal fun File.isKotlinFile() = hasFileExtension(listOf("kt", "kts"))
+internal fun File.hasKotlinFileExtension() = hasFileExtension(listOf("kt", "kts"))
 
-internal fun File.isJavaFile() = hasFileExtension(listOf("java"))
+internal fun File.hasJavaFileExtension() = hasFileExtension(listOf("java"))
 
 internal fun File.hasFileExtension(extensions: List<String>)
     = extensions.any{ it.equals(extension, ignoreCase = true) }

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

@@ -466,7 +466,7 @@ class KotlinCompilationTests {
 	@Test
 	fun `Kotlin AP sees Java class`() {
 		val jSource = SourceFile.java(
-			"JSource.kt", """
+			"JSource.java", """
 				package com.tschuchort.compiletesting;
 			
 				@ProcessElem