Unexpected stack overflow error during serialization of an acyclic graph of nested structures

[plokhotnyuk]

To reproduce, please uncomment the following test and method that it calls:
https://github.com/plokhotnyuk/jsoniter-scala/pull/127/files#diff-feb5716779d1ff5fbe1a4af25bb4ae6dR19

[ghik]

Hello, thanks for the report.
The problem is in this line: https://github.com/plokhotnyuk/jsoniter-scala/blob/3f81687acabc30202d43c2a9f31fb541fb342112/benchmark/src/main/scala/com/github/plokhotnyuk/jsoniter_scala/macros/AVSystemCodecs.scala#L48

implicit val twitterAPIGenCodec: GenCodec[Seq[Tweet]] = GenCodec.materializeRecursively[Seq[Tweet]]

You should not macro-materialize codec for a Seq, because GenCodec[Seq[A]] is automatically provided as long as there is a GenCodec[A], so this would be sufficient:

implicit val twitterAPIGenCodec: GenCodec[Tweet] = GenCodec.materializeRecursively[Tweet]

... but I just realized that it doesn't work because GenCodec cannot be materialized for case classes with more than 22 fields 😢
Also, the macro itself should be more secured to reject materializing something like a Seq.
Will fix that.

[ghik]

This is interesting. It turns out that Seq[A] is actually a completely valid type for macro materialization of GenCodec because it has a companion object with matching apply and unapplySeq methods. The only problem is that the argument of apply is also a Seq[A] which creates a cycle and causes stack to overflow.

[plokhotnyuk]

Stack overflow cannot be reproduced by this code with v1.28.2, but JsonStringInput.read[Seq[Tweet]] returns an instance of Vector instead of expected List:
https://github.com/plokhotnyuk/jsoniter-scala/blob/7aa20826271d03262b734caa40d818bda5f725d3/jsoniter-scala-benchmark/src/main/scala/com/github/plokhotnyuk/jsoniter_scala/macros/TwitterAPIBenchmark.scala#L25-L28

Should I close this issue and open a new one for that case?

[ghik]

@plokhotnyuk I've created separate issue for that, closing this one. Thanks!