typelevel / typelevel/cats

FreeT is stack-unsafe

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#3,550 2 comments 0 reactions 0 assignees View on GitHub

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Dominant language
Scala
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Description

...somehow.

	at cats.free.FreeT.$anonfun$step$1(FreeT.scala:163)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:85)
	at cats.free.FreeT.$anonfun$step$1(FreeT.scala:163)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:85)
	at cats.free.FreeT.$anonfun$step$1(FreeT.scala:163)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:85)
	at cats.free.FreeT.$anonfun$step$1(FreeT.scala:163)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:85)
	at cats.free.FreeT.$anonfun$step$1(FreeT.scala:163)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:85)
	at cats.free.FreeT.$anonfun$step$1(FreeT.scala:163)
	at scala.Function1.$anonfun$andThen$1(Function1.scala:85)

That goes on for a while and turns into an SOE. Staring at the source code, it looks like a recursive flatMap is causing it, but it's hard to say exactly.

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with cats.free.FreeT.scala around line 163 and reproduce the reported stack overflow, focusing on the repeated step and flatMap-related calls in the trace. The issue does not identify a test or a precise reproduction, so first determine the triggering operation; done means the reported recursion no longer overflows the stack.

Written by the indexing model from the issue text.

Assessment

Tech stack
scala
Domain
developer-experience
Issue type
Bug
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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