1 files changed, 36 insertions, 0 deletions
diff --git a/src/main/scala/firrtl/options/phases/WriteOutputAnnotations.scala b/src/main/scala/firrtl/options/phases/WriteOutputAnnotations.scala
new file mode 100644
index 00000000..bb2a8cd6
--- /dev/null
+++ b/src/main/scala/firrtl/options/phases/WriteOutputAnnotations.scala
@@ -0,0 +1,36 @@
+// See LICENSE for license details.
+
+package firrtl.options.phases
+
+import firrtl.AnnotationSeq
+import firrtl.annotations.{DeletedAnnotation, JsonProtocol}
+import firrtl.options.{Phase, StageOptions, Unserializable, Viewer}
+
+import java.io.PrintWriter
+
+/** [[firrtl.options.Phase Phase]] that writes an [[AnnotationSeq]] to a file. A file is written if and only if a
+  * [[StageOptions]] view has a non-empty [[StageOptions.annotationFileOut annotationFileOut]].
+  */
+class WriteOutputAnnotations extends Phase {
+
+  /** Write the input [[AnnotationSeq]] to a fie. */
+  def transform(annotations: AnnotationSeq): AnnotationSeq = {
+    val sopts = Viewer[StageOptions].view(annotations)
+    val serializable = annotations.filter{
+      case _: Unserializable    => false
+      case _: DeletedAnnotation => sopts.writeDeleted
+      case _                    => true
+    }
+
+    sopts.annotationFileOut match {
+      case None =>
+      case Some(file) =>
+        val pw = new PrintWriter(sopts.getBuildFileName(file, Some(".anno.json")))
+        pw.write(JsonProtocol.serialize(serializable))
+        pw.close()
+    }
+
+    annotations
+  }
+
+}