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ErrorAccumulatingUnmarshaller from akka-http-json lib no longer applying validations in 0.9.2

See original GitHub issue

We have some Decoders with attached validations like this:

implicit val decodeSomething = deriveDecoder[Something].validate(..., ...)

And we use this for our akka-http routes (https://github.com/hseeberger/akka-http-json):

trait AkkaHttpCirceSupport extends BaseCirceSupport with ErrorAccumulatingUnmarshaller

And after updating to 0.9.2 that validation is no longer applied.

Switching to FailFastCirceSupport makes the validation run again. It’s probably related to https://github.com/circe/circe/pull/838/files, but I’m not sure.

Reverting to 0.9.1 makes ErrorAccumulatingUnmarshaller run validations again.

I put together a couple of tests showing this here: https://github.com/yurique/akka-http-json-fail/tree/validation-fail (validation-fail branch)

sbt test fails in one of the cases; changing circe to v0.9.1 makes them pass.

I’m not sure if this is related to circe or to akka-http-json lib.

/cc @hseeberger