Validate modifier reordering runtime support

Author: mkurz

README.md

@@ -38,7 +38,7 @@ For available versions see [releases](https://github.com/sbt/sbt-java-formatter/
 * The `javafmtRemoveUnusedImports` setting controls whether unused imports are removed (`true` by default).
 * The `javafmtReflowLongStrings` setting controls whether long string literals are reflowed (`true` by default).
 * The `javafmtFormatJavadoc` setting controls whether Javadoc comments are reformatted (`true` by default).
-* The `javafmtReorderModifiers` setting controls whether modifiers are reordered into JLS order (`true` by default).
+* The `javafmtReorderModifiers` setting controls whether modifiers are reordered into JLS order (`true` by default). Disabling it requires `javafmtFormatterCompatibleJavaVersion := 21`.
 * The `javafmtFormatterCompatibleJavaVersion` setting selects which `google-java-format` runtime line to use (`21` by default).
 * The `javafmtJavaMaxHeap` setting controls the maximum heap passed to the forked `google-java-format` JVM (`Some("256m")` by default).
 

plugin/src/main/scala/com/github/sbt/JavaFormatterPlugin.scala

@@ -143,7 +143,8 @@ object JavaFormatterPlugin extends AutoPlugin {
         val iF = (javafmt / includeFilter).value
         val eF = (javafmt / excludeFilter).value
         val cache = streamz.cacheStoreFactory
-        val options = javafmtOptions.value
+        val options =
+          validateOptions(javafmtOptions.value, javafmtFormatterCompatibleJavaVersion.value)
         val formatterClasspath = javafmtFormatterClasspath.value.toVector
         val javaMaxHeap = javafmtJavaMaxHeap.value
         val sortImports = javafmtSortImports.value
@@ -173,7 +174,8 @@ object JavaFormatterPlugin extends AutoPlugin {
         val iF = (javafmt / includeFilter).value
         val eF = (javafmt / excludeFilter).value
         val cache = (javafmt / streams).value.cacheStoreFactory
-        val options = javafmtOptions.value
+        val options =
+          validateOptions(javafmtOptions.value, javafmtFormatterCompatibleJavaVersion.value)
         val formatterClasspath = javafmtFormatterClasspath.value.toVector
         val javaMaxHeap = javafmtJavaMaxHeap.value
         val sortImports = javafmtSortImports.value
@@ -203,7 +205,8 @@ object JavaFormatterPlugin extends AutoPlugin {
         val iF = (javafmt / includeFilter).value
         val eF = (javafmt / excludeFilter).value
         val cache = streamz.cacheStoreFactory
-        val options = javafmtOptions.value
+        val options =
+          validateOptions(javafmtOptions.value, javafmtFormatterCompatibleJavaVersion.value)
         val formatterClasspath = javafmtFormatterClasspath.value.toVector
         val javaMaxHeap = javafmtJavaMaxHeap.value
         val sortImports = javafmtSortImports.value
@@ -233,7 +236,8 @@ object JavaFormatterPlugin extends AutoPlugin {
         val iF = (javafmt / includeFilter).value
         val eF = (javafmt / excludeFilter).value
         val cache = (javafmt / streams).value.cacheStoreFactory
-        val options = javafmtOptions.value
+        val options =
+          validateOptions(javafmtOptions.value, javafmtFormatterCompatibleJavaVersion.value)
         val formatterClasspath = javafmtFormatterClasspath.value.toVector
         val javaMaxHeap = javafmtJavaMaxHeap.value
         val sortImports = javafmtSortImports.value
@@ -289,6 +293,17 @@ object JavaFormatterPlugin extends AutoPlugin {
           s"Unsupported javafmtFormatterCompatibleJavaVersion: $other. Expected one of: 11, 17, 21.")
     }
 
+  private def validateOptions(options: JavaFormatterOptions, compatibleJavaVersion: Int): JavaFormatterOptions = {
+    if (!options.reorderModifiers() && compatibleJavaVersion != 21) {
+      throw new MessageOnlyException(
+        "Disabling modifier reordering requires " +
+        "ThisBuild / javafmtFormatterCompatibleJavaVersion := 21 " +
+        "because the Java 11 and Java 17 formatter runtime lines do not support " +
+        "--skip-reordering-modifiers.")
+    }
+    options
+  }
+
   @transient
   private val javafmtDoFormatOnCompile =
     taskKey[Unit]("Format Java source files if javafmtOnCompile is on.")

plugin/src/sbt-test/sbt-java-formatter/reorder-modifiers-unsupported/src/main/java/com/lightbend/BadFormatting.java

@@ -1,2 +1,2 @@
-ThisBuild / javafmtFormatterCompatibleJavaVersion := 11
+ThisBuild / javafmtFormatterCompatibleJavaVersion := 21
 ThisBuild / javafmtReorderModifiers := false

plugin/src/sbt-test/sbt-java-formatter/reorder-modifiers/build.sbt

@@ -3,3 +3,6 @@
 > javafmtCheck
 
 $ exec diff src/main/java/com/lightbend/BadFormatting.java src/main/java-expected/com/lightbend/BadFormatting.java
+
+> set ThisBuild / javafmtFormatterCompatibleJavaVersion := 17
+-> javafmtCheck