Hi, I've just started using coroutines… I'm trying to parse JSON (with Jackson) in a `suspend fun`, ...

# coroutines

[hho]

Hi, I've just started using coroutines… I'm trying to parse JSON (with Jackson) in a suspend fun, and the "Inappropriate blocking method call" inspection flags my code:

val message = objectMapper.readTree(inputString)

What can I do about it? It's not doing I/O, it's operating on a String.

[Yan Pujante]

If you use the annotation @Suppress("UNCHECKED_CAST", "BlockingMethodInNonBlockingContext") it will remove the warning. I assume because it is actually not blocking it is the right thing to do, but I am no expert in coroutines...

[streetsofboston]

The code 'linter' assumes that any method (block of code) that throws an IOException (or a sub-class of it) is blocking. This assumption is often right but also often wrong 🙂

[hho]

Ah, that explains it. Thank you both, I'll go with suppressing the warning for now.

[ephemient]

https://youtrack.jetbrains.com/issue/KTIJ-838
https://youtrack.jetbrains.com/issue/KTIJ-840

[gildor]

Also in this particular case it depends how big json is, it can be a heavy computation, but probably if you use string it's not so big

[hho]

You're right, it's <2kB.
What would be the right way to do this, if this gets larger?

[gildor]

use another readTree overload and pass there Reader/InputStream and wrap this line to IO dispatcher (if this InputStream/Reader is reading from network/disk) or with Default dispatcher (if it some runtime-generated JSON, so there is a chance that CPU is bottle neck)