Fix javac version parsing for version strings without minorv and add tests

Author: tschuchortdev

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

@@ -2,12 +2,12 @@ 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
 import javax.tools.JavaFileObject
 import javax.tools.SimpleJavaFileObject
+import kotlin.IllegalArgumentException
 
 /**
  * A [JavaFileObject] created from a source [File].
@@ -81,12 +81,22 @@ internal fun getJavacVersionString(javacCommand: String): String {
 }
 
 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'")
+    try {
+        val (majorv, minorv, patchv, otherv) = Regex("([0-9]*)(?:\\.([0-9]*))?(?:\\.([0-9]*))?(.*)")
+            .matchEntire(javacVersionString)?.destructured
+            ?: throw IllegalArgumentException("Could not match version regex")
 
-    return (majorv.toInt() == 1 && minorv.toInt() >= 9) // old versioning scheme: 1.8.x
-            || (majorv.toInt() >= 9) // new versioning scheme: 10.x.x
+        check(majorv.isNotBlank()) { "Major version can not be blank" }
+
+        if (majorv.toInt() == 1)
+            check(minorv.isNotBlank()) { "Minor version can not be blank if major version is 1" }
+
+        return (majorv.toInt() == 1 && minorv.toInt() >= 9) // old versioning scheme: 1.8.x
+                || (majorv.toInt() >= 9) // new versioning scheme: 10.x.x
+    }
+    catch (t: Throwable) {
+        throw IllegalArgumentException("Could not parse javac version string: '$javacVersionString'", t)
+    }
 }
 
 /** Finds the tools.jar given a path to a JDK 8 or earlier */

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

@@ -0,0 +1,42 @@
+package com.tschuchort.compiletesting
+
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class JavacUtilsTest {
+
+    @Test
+    fun `Old version scheme less than 9 is parsed correctly`() {
+        assertFalse(isJavac9OrLater("1.8.0"))
+    }
+
+    @Test
+    fun `Old version scheme greater equal 9 is parsed correctly`() {
+        assertTrue(isJavac9OrLater("1.9.1"))
+        assertTrue(isJavac9OrLater("1.11.0"))
+    }
+
+    @Test
+    fun `New version scheme less than 9 is parsed correctly`() {
+        assertFalse(isJavac9OrLater("8.1.0.1"))
+        assertFalse(isJavac9OrLater("8.1.0"))
+        assertFalse(isJavac9OrLater("8.1"))
+        assertFalse(isJavac9OrLater("8"))
+    }
+
+    @Test
+    fun `New version scheme greater equal 9 is parsed correctly`() {
+        assertTrue(isJavac9OrLater("9.0.0.1"))
+        assertTrue(isJavac9OrLater("9.0.0"))
+        assertTrue(isJavac9OrLater("9.1.0"))
+        assertTrue(isJavac9OrLater("9.1"))
+        assertTrue(isJavac9OrLater("9"))
+        assertTrue(isJavac9OrLater("12"))
+    }
+
+    @Test
+    fun `Old version scheme with extra info is parsed correctly`() {
+        assertTrue(isJavac9OrLater("1.11.0-bla"))
+    }
+}