fkhaidari · fkhaidari · Apr 26, 2026
diff --git a/core/src/main/scala-2/chisel3/debug/CtorParamsPlatform.scala b/core/src/main/scala-2/chisel3/debug/CtorParamsPlatform.scala
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package chisel3.debug
+
+import scala.reflect.runtime.universe._
+
+private[debug] object CtorParamsPlatform {
+
+  def ctorParams(obj: Any): Seq[(String, String)] = {
+    val ctor = typeOfInstance(obj).typeSymbol.asClass.primaryConstructor
+    if (ctor == NoSymbol) Seq.empty
+    else
+      ctor.asMethod.paramLists.flatten
+        .filter(!_.name.toString.contains("$outer"))
+        .map(a => (a.name.toString.trim, a.info.typeSymbol.name.decodedName.toString.trim))
+  }
+
+  private def typeOfInstance(obj: Any): Type =
+    runtimeMirror(obj.getClass.getClassLoader).classSymbol(obj.getClass).toType
+}
diff --git a/core/src/main/scala-3/chisel3/debug/CtorParamsPlatform.scala b/core/src/main/scala-3/chisel3/debug/CtorParamsPlatform.scala
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package chisel3.debug
+
+import logger.LazyLogging
+
+// Scala 3 has no runtime mirror to pick a primary out of multiple ctors,
+// so emit params only for single-ctor classes.
+private[debug] object CtorParamsPlatform extends LazyLogging {
+
+  def ctorParams(obj: Any): Seq[(String, String)] = {
+    val cls = obj.getClass
+    val ctors = cls.getDeclaredConstructors
+    if (ctors.length != 1) {
+      if (ctors.length > 1)
+        logger.warn(s"ctorParams: ${cls.getName} has ${ctors.length} constructors; omitting `params`")
+      Seq.empty
+    } else {
+      val rawParams = ctors.head.getParameters.toSeq.filter(!_.getName.contains("$outer"))
+      val namesSynthetic = rawParams.nonEmpty && rawParams.forall(!_.isNamePresent)
+      val params = rawParams.map(p => (p.getName, simpleTypeName(p.getParameterizedType.getTypeName)))
+      if (namesSynthetic)
+        logger.warn(
+          s"ctorParams: ${cls.getName} has only synthetic parameter names " +
+            s"(${params.map(_._1).mkString(", ")}); emitted debug metadata will be of limited use. " +
+            s"Compile user code with a flag that retains parameter names " +
+            s"(e.g. javac `-parameters`) to recover real names."
+        )
+      params
+    }
+  }
+
+  private def simpleTypeName(raw: String): String = {
+    val noGeneric = raw.takeWhile(_ != '<')
+    val afterDot = noGeneric.substring(noGeneric.lastIndexOf('.') + 1)
+    val lastDollar = afterDot.lastIndexOf('$')
+    val name = if (lastDollar >= 0) afterDot.substring(lastDollar + 1) else afterDot
+    name.capitalize
+  }
+}
diff --git a/core/src/main/scala/chisel3/debug/DebugMeta.scala b/core/src/main/scala/chisel3/debug/DebugMeta.scala
@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package chisel3.debug
+
+import logger.LazyLogging
+
+import chisel3._
+
+import upickle.{default => json}
+
+import scala.collection.mutable
+import scala.language.existentials
+import scala.util.Try
+import scala.util.control.NonFatal
+
+private[debug] case class ClassParam(
+  name:     String,
+  typeName: String,
+  value:    Option[ujson.Value] = None
+)
+
+private[debug] object ClassParam {
+  implicit val rw: json.ReadWriter[ClassParam] = json
+    .readwriter[ujson.Value]
+    .bimap(
+      p =>
+        ujson.Obj(
+          "name" -> p.name,
+          "typeName" -> p.typeName,
+          "value" -> p.value.getOrElse(ujson.Null)
+        ),
+      j =>
+        ClassParam(
+          j("name").str,
+          j("typeName").str,
+          j.obj.get("value").filterNot(_ == ujson.Null)
+        )
+    )
+}
+
+private[debug] object CtorParamExtractor {
+  private[debug] val MaxParamDepth = 8
+  private[debug] val MaxRenderedLen = 256
+  private[debug] val TruncatedSuffix = "...[truncated]"
+
+  private[debug] def dataToTypeName(data: Data): String = sanitize(data match {
+    case t: Record =>
+      t.topBindingOpt match {
+        case Some(binding) => s"${t._bindingToString(binding)}[${t.className}]"
+        case None          => t.className
+      }
+    case t => t.toString.split(" ").last
+  })
+
+  private def sanitize(s: String): String =
+    s.replaceAll("[\\p{Cntrl}\"\\\\]", "")
+
+  private[debug] def getCtorParams(target: Any): Seq[ClassParam] =
+    new CtorParamExtractor().getCtorParams(target)
+}
+
+private[debug] final class CtorParamExtractor extends LazyLogging {
+  import CtorParamExtractor.{dataToTypeName, MaxParamDepth, MaxRenderedLen, TruncatedSuffix}
+
+  private case class ClassDescriptor(
+    params:    Seq[(String, String)],
+    accessors: Map[String, java.lang.reflect.Method]
+  )
+
+  private val descriptorCache = mutable.HashMap.empty[Class[_], ClassDescriptor]
+  // Identity-keyed; depth bounded by MaxParamDepth so linear scan beats hashing.
+  // Reset at every getCtorParams entry; safe because elaboration is single-threaded.
+  private val visited = mutable.ArrayBuffer.empty[AnyRef]
+
+  private def descriptor(target: Any): ClassDescriptor = {
+    val cls = target.getClass
+    descriptorCache.getOrElseUpdate(cls, buildDescriptor(target, cls))
+  }
+
+  private def buildDescriptor(target: Any, cls: Class[_]): ClassDescriptor = {
+    val params =
+      try CtorParamsPlatform.ctorParams(target)
+      catch {
+        case NonFatal(e) =>
+          logger.debug(s"ctorParams failed on ${cls.getName}: ${e.getMessage}")
+          Seq.empty[(String, String)]
+      }
+    val accessors = params.iterator.flatMap { case (name, _) =>
+      try {
+        val m = cls.getDeclaredMethod(name)
+        m.setAccessible(true)
+        Some(name -> m)
+      } catch { case NonFatal(_) => None }
+    }.toMap
+    ClassDescriptor(params, accessors)
+  }
+
+  private[debug] def getCtorParams(target: Any): Seq[ClassParam] = {
+    visited.clear()
+    target match { case ref: AnyRef => visited += ref; case _ => }
+    getCtorParamsImpl(target, 0)
+  }
+
+  private def getCtorParamsImpl(target: Any, depth: Int): Seq[ClassParam] = {
+    val d = descriptor(target)
+    d.params.map { case (name, typeName) =>
+      ClassParam(name, typeName, paramValue(target, d, name, typeName, depth))
+    }
+  }
+
+  private def paramValue(
+    obj:      Any,
+    desc:     ClassDescriptor,
+    name:     String,
+    typeName: String,
+    depth:    Int
+  ): Option[ujson.Value] =
+    desc.accessors.get(name).flatMap { method =>
+      Try(method.invoke(obj.asInstanceOf[AnyRef])).fold(
+        e => { logger.debug(s"paramValue: cannot reflect $name: ${e.getMessage}"); None },
+        v => Some(renderValue(v, typeName, depth))
+      )
+    }
+
+  private def renderValue(v: Any, typeName: String, depth: Int): ujson.Value = v match {
+    case s: scala.collection.Seq[_] if s.exists(_.isInstanceOf[Data]) =>
+      ujson.Str(s.collect { case d: Data => dataToTypeName(d) }.mkString("[", ", ", "]"))
+    case d: Data    => ujson.Str(dataToTypeName(d))
+    case b: Boolean => ujson.Bool(b)
+    case _: Byte | _: Short | _: Int | _: Long | _: Float | _: Double => ujson.Str(v.toString)
+    case null                                                         => ujson.Str("null")
+    case ref: AnyRef =>
+      if (depth >= MaxParamDepth || visited.exists(_ eq ref) || isOpaqueStdlibClass(ref.getClass))
+        ujson.Str(capped(ref.toString))
+      else {
+        visited += ref
+        val nested =
+          try getCtorParamsImpl(ref, depth + 1)
+          finally visited.dropRightInPlace(1)
+        if (nested.exists(_.value.isDefined))
+          ujson.Str(
+            capped(
+              s"$typeName(${nested.map(p => p.value.fold(p.name)(vv => s"${p.name}: ${renderJson(vv)}")).mkString(", ")})"
+            )
+          )
+        else ujson.Str(capped(ref.toString))
+      }
+    case other => ujson.Str(capped(other.toString))
+  }
+
+  private def renderJson(v: ujson.Value): String = v match {
+    case ujson.Str(s)  => s
+    case ujson.Bool(b) => b.toString
+    case ujson.Num(n)  => if (n.isWhole && !n.isInfinity) n.toLong.toString else n.toString
+    case other         => other.toString
+  }
+
+  private def capped(s: String): String =
+    if (s.length <= MaxRenderedLen) s else s.substring(0, MaxRenderedLen) + TruncatedSuffix
+
+  private def isOpaqueStdlibClass(cls: Class[_]): Boolean = {
+    val name = cls.getName
+    name.startsWith("java.") || name.startsWith("javax.") ||
+    name.startsWith("sun.") || name.startsWith("scala.")
+  }
+}