Patch target to match Scala 2.11/2.12 scalac option syntax, close #583

Motivation:

We can't directly pass a target that's valid for javac to scalac prior to 2.13 as it was using a different syntax.

Author: slandelle

src/main/java/scala_maven/ScalaMojoSupport.java

@@ -584,6 +584,34 @@ private String getToolClasspath() throws Exception {
     return FileUtils.toMultiPath(classpath);
   }
 
+  static String targetOption(String target, VersionNumber scalaVersion) {
+    if (scalaVersion.major == 2) {
+      if (scalaVersion.minor <= 12) {
+        if (target.equals("1.5") || target.equals("5")) {
+          return "jvm-1.5";
+        } else if (target.equals("1.6") || target.equals("6")) {
+          return "jvm-1.6";
+        } else if (target.equals("1.7") || target.equals("7")) {
+          return "jvm-1.7";
+        } else if (target.equals("1.8") || target.equals("8")) {
+          return "jvm-1.8";
+        } else {
+          // invalid or unsupported option, just ignore
+          return null;
+        }
+      } else if (target.equals("1.5")) {
+        return "5";
+      } else if (target.equals("1.6")) {
+        return "6";
+      } else if (target.equals("1.7")) {
+        return "7";
+      } else if (target.equals("1.8")) {
+        return "8";
+      }
+    }
+    return target;
+  }
+
   protected List<String> getScalacOptions() throws Exception {
     List<String> options = new ArrayList<>();
     if (args != null) Collections.addAll(options, args);
@@ -593,7 +621,10 @@ protected List<String> getScalacOptions() throws Exception {
     options.addAll(getCompilerPluginOptions());
 
     if (target != null && !target.isEmpty()) {
-      options.add("-target:" + target);
+      String targetOption = targetOption(target, findScalaVersion());
+      if (targetOption != null) {
+        options.add("-target:" + targetOption);
+      }
     }
     if (release != null && !release.isEmpty()) {
       options.add("-release");

src/test/java/scala_maven/ScalaMojoSupportTest.java

@@ -0,0 +1,63 @@
+/*
+ * This is free and unencumbered software released into the public domain.
+ * See UNLICENSE.
+ */
+package scala_maven;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import org.junit.Test;
+
+public class ScalaMojoSupportTest {
+
+  @Test
+  public void scala2_11_should_generate_prefixed_target() {
+    assertEquals("jvm-1.5", ScalaMojoSupport.targetOption("1.5", new VersionNumber("2.11.12")));
+    assertEquals("jvm-1.5", ScalaMojoSupport.targetOption("5", new VersionNumber("2.11.12")));
+    assertEquals("jvm-1.6", ScalaMojoSupport.targetOption("1.6", new VersionNumber("2.11.12")));
+    assertEquals("jvm-1.6", ScalaMojoSupport.targetOption("6", new VersionNumber("2.11.12")));
+    assertEquals("jvm-1.7", ScalaMojoSupport.targetOption("1.7", new VersionNumber("2.11.12")));
+    assertEquals("jvm-1.7", ScalaMojoSupport.targetOption("7", new VersionNumber("2.11.12")));
+    assertEquals("jvm-1.8", ScalaMojoSupport.targetOption("1.8", new VersionNumber("2.11.12")));
+    assertEquals("jvm-1.8", ScalaMojoSupport.targetOption("8", new VersionNumber("2.11.12")));
+  }
+
+  @Test
+  public void scala2_11_should_generate_null_for_unsupported_java_versions() {
+    assertNull(ScalaMojoSupport.targetOption("11", new VersionNumber("2.11.12")));
+    assertNull(ScalaMojoSupport.targetOption("17", new VersionNumber("2.11.12")));
+  }
+
+  @Test
+  public void scala2_12_should_generate_prefixed_target() {
+    assertEquals("jvm-1.5", ScalaMojoSupport.targetOption("1.5", new VersionNumber("2.12.11")));
+    assertEquals("jvm-1.5", ScalaMojoSupport.targetOption("5", new VersionNumber("2.12.11")));
+    assertEquals("jvm-1.6", ScalaMojoSupport.targetOption("1.6", new VersionNumber("2.12.11")));
+    assertEquals("jvm-1.6", ScalaMojoSupport.targetOption("6", new VersionNumber("2.12.11")));
+    assertEquals("jvm-1.7", ScalaMojoSupport.targetOption("1.7", new VersionNumber("2.12.11")));
+    assertEquals("jvm-1.7", ScalaMojoSupport.targetOption("7", new VersionNumber("2.12.11")));
+    assertEquals("jvm-1.8", ScalaMojoSupport.targetOption("1.8", new VersionNumber("2.12.11")));
+    assertEquals("jvm-1.8", ScalaMojoSupport.targetOption("8", new VersionNumber("2.12.11")));
+  }
+
+  @Test
+  public void scala2_12_should_generate_null_for_unsupported_java_versions() {
+    assertNull(ScalaMojoSupport.targetOption("11", new VersionNumber("2.12.11")));
+    assertNull(ScalaMojoSupport.targetOption("17", new VersionNumber("2.12.11")));
+  }
+
+  @Test
+  public void scala2_13_should_generate_non_prefixed_target() {
+    assertEquals("5", ScalaMojoSupport.targetOption("1.5", new VersionNumber("2.13.8")));
+    assertEquals("5", ScalaMojoSupport.targetOption("5", new VersionNumber("2.13.8")));
+    assertEquals("6", ScalaMojoSupport.targetOption("1.6", new VersionNumber("2.13.8")));
+    assertEquals("6", ScalaMojoSupport.targetOption("6", new VersionNumber("2.13.8")));
+    assertEquals("7", ScalaMojoSupport.targetOption("1.7", new VersionNumber("2.13.8")));
+    assertEquals("7", ScalaMojoSupport.targetOption("7", new VersionNumber("2.13.8")));
+    assertEquals("8", ScalaMojoSupport.targetOption("1.8", new VersionNumber("2.13.8")));
+    assertEquals("8", ScalaMojoSupport.targetOption("8", new VersionNumber("2.13.8")));
+    assertEquals("11", ScalaMojoSupport.targetOption("11", new VersionNumber("2.13.8")));
+    assertEquals("17", ScalaMojoSupport.targetOption("17", new VersionNumber("2.13.8")));
+  }
+}