Use javac from provided JDK. Add a bunch of unit tests

Author: tschuchortdev

.idea/misc.xml

@@ -1,5 +1,7 @@
-import java.io.IOException
-import java.io.OutputStream
+package com.tschuchort.compiletesting
+
+import java.io.*
+
 
 /** An output stream that does nothing, like /dev/null */
 internal object NullStream : OutputStream() {

src/main/kotlin/StreamUtils.kt renamed to src/main/kotlin/com/tschuchort/compiletesting/StreamUtils.kt

@@ -0,0 +1,35 @@
+package com.tschuchort.compiletesting
+
+import java.io.File
+import javax.lang.model.SourceVersion
+
+internal fun <E> MutableCollection<E>.addAll(vararg elems: E) = addAll(elems)
+
+internal fun getJavaHome(): File {
+    val path = System.getProperty("java.home")
+        ?: throw IllegalStateException("no java home found")
+
+    return File(path).also { check(it.isDirectory) }
+}
+
+internal fun getJdkHome()
+    = if(isJdk9OrLater())
+        getJavaHome()
+    else
+        getJavaHome().parentFile
+
+/** Checks if the JDK of the host process is version 9 or later */
+internal fun isJdk9OrLater(): Boolean
+        = SourceVersion.latestSupported().compareTo(SourceVersion.RELEASE_8) > 0
+
+internal fun File.listFilesRecursively(): List<File> {
+    return listFiles().flatMap { file ->
+        if(file.isDirectory)
+            file.listFilesRecursively()
+        else
+            listOf(file)
+    }
+}
+
+internal fun File.isKotlinFile()
+        = listOf("kt", "kts").any{ it.equals(extension, ignoreCase = true) }

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

@@ -1,3 +1,5 @@
+package com.tschuchort.compiletesting;
+
 import com.squareup.javapoet.JavaFile;
 import com.squareup.kotlinpoet.FileSpec;
 import com.squareup.kotlinpoet.FunSpec;
@@ -56,14 +58,15 @@ public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment
                 ).build();
             }
 
-            FileSpec fileSpec = FileSpec.builder("", "JavaGeneratedKotlinClass.kt")
+            FileSpec fileSpec = FileSpec.builder("com.tschuchort.compiletesting", "JavaGeneratedKotlinClass.kt")
                     .addType(typeSpecBuilder.build())
                     .build();
 
             writeKotlinFile(fileSpec, fileSpec.getName(), fileSpec.getPackageName());
 
             try {
-                JavaFile.builder("", com.squareup.javapoet.TypeSpec.classBuilder("JavaGeneratedJavaClass").build())
+                JavaFile.builder("com.tschuchort.compiletesting",
+                        com.squareup.javapoet.TypeSpec.classBuilder("JavaGeneratedJavaClass").build())
                         .build().writeTo(processingEnv.getFiler());
             } catch (Exception e) {
             }

src/test/java/JavaTestProcessor.java renamed to src/test/java/com/tschuchort/compiletesting/JavaTestProcessor.java

@@ -1,4 +1,8 @@
+package com.tschuchort.compiletesting
+
+import okio.Buffer
 import java.io.*
+import java.lang.IllegalArgumentException
 import java.net.URI
 import java.nio.charset.Charset
 import javax.tools.JavaCompiler
@@ -11,7 +15,9 @@ import javax.tools.SimpleJavaFileObject
  * Used for interfacing with javac ([JavaCompiler]).
  */
 internal class FileJavaFileObject(val sourceFile: File, val charset: Charset = Charset.defaultCharset())
-    : SimpleJavaFileObject(sourceFile.toURI(), deduceKind(sourceFile.toURI())) {
+    : SimpleJavaFileObject(sourceFile.toURI(),
+    deduceKind(sourceFile.toURI())
+) {
 
     init {
         require(sourceFile.isFile)
@@ -51,4 +57,34 @@ internal class StringJavaFileObject(className: String, private val contents: Str
     override fun openReader(ignoreEncodingErrors: Boolean): Reader = StringReader(contents)
 
     override fun getLastModified(): Long = _lastModified
+}
+
+/**
+ * Gets the version string of a javac executable that can be started using the
+ * given [javacCommand] via [Runtime.exec].
+ */
+internal fun getJavacVersionString(javacCommand: String): String {
+    val javacProc = ProcessBuilder(listOf(javacCommand, "-version"))
+        .redirectErrorStream(true)
+        .start()
+
+    val buffer = Buffer()
+
+    javacProc.inputStream.copyTo(buffer.outputStream())
+    javacProc.waitFor()
+
+    val output = buffer.readUtf8()
+
+    return Regex("javac (.*)?[\\s\\S]*").matchEntire(output)?.destructured?.component1()
+        ?: throw IllegalStateException("Command '$javacCommand -version' did not print expected output. " +
+                "Output was: '$output'")
+}
+
+internal fun isJavac9OrLater(javacVersionString: String): Boolean {
+    val (majorv, minorv, patchv, otherv) = Regex("([0-9]*)\\.([0-9]*)\\.([0-9]*)(.*)")
+        .matchEntire(javacVersionString)?.destructured
+        ?: throw IllegalArgumentException("Could not parse javac version string: '$javacVersionString'")
+
+    return (majorv.toInt() == 1 && minorv.toInt() >= 9) // old versioning scheme: 1.8.x
+            || (majorv.toInt() >= 9) // new versioning scheme: 10.x.x
 }