1 files changed, 43 insertions, 0 deletions
diff --git a/src/main/scala/firrtl/options/phases/Checks.scala b/src/main/scala/firrtl/options/phases/Checks.scala
new file mode 100644
index 00000000..0691e9b0
--- /dev/null
+++ b/src/main/scala/firrtl/options/phases/Checks.scala
@@ -0,0 +1,43 @@
+// See LICENSE for license details.
+
+package firrtl.options.phases
+
+import firrtl.AnnotationSeq
+import firrtl.annotations.Annotation
+import firrtl.options.{OptionsException, OutputAnnotationFileAnnotation, Phase, TargetDirAnnotation}
+
+/** [[firrtl.options.Phase Phase]] that validates an [[AnnotationSeq]]. If successful, views of this [[AnnotationSeq]]
+  * as [[StageOptions]] are guaranteed to succeed.
+  */
+class Checks extends Phase {
+
+  /** Validate an [[AnnotationSeq]] for [[StageOptions]]
+    * @throws OptionsException if annotations are invalid
+    */
+  def transform(annotations: AnnotationSeq): AnnotationSeq = {
+
+    val td, outA = collection.mutable.ListBuffer[Annotation]()
+    annotations.foreach {
+      case a: TargetDirAnnotation => td += a
+      case a: OutputAnnotationFileAnnotation => outA += a
+      case _ =>
+    }
+
+    if (td.size != 1) {
+      val d = td.map{ case TargetDirAnnotation(x) => x }
+      throw new OptionsException(
+        s"""|Exactly one target directory must be specified, but found `${d.mkString(", ")}` specified via:
+            |    - explicit target directory: -td, --target-dir, TargetDirAnnotation
+            |    - fallback default value""".stripMargin )}
+
+    if (outA.size > 1) {
+      val x = outA.map{ case OutputAnnotationFileAnnotation(x) => x }
+      throw new OptionsException(
+        s"""|At most one output annotation file can be specified, but found '${x.mkString(", ")}' specified via:
+            |    - an option or annotation: -foaf, --output-annotation-file, OutputAnnotationFileAnnotation"""
+          .stripMargin )}
+
+    annotations
+  }
+
+}