when calling a

suspend fun

exposed from a library like

Retrofit

or

Room

or

SqlDelight

- is there a need to change the dispatcher to

IO

or since they are code generating a

suspend fun

is it safe to assume that its ‘main-safe’?

Retrofit and SQLDelight are safe

Wait, SQLDelight is exposing suspending functions?

i think i may have misspoke on that (unless something has changed in the past few months)

it exposes Flow

I knew about Flow, but that's not suspending functions. You need to make sure you execute the resulting

Query

objects on

<http://Dispatchers.IO|Dispatchers.IO>

to be main-safe. (That is not an argument for Room)

is Room not main-safe by default? trying to research a bit but haven’t found out yet

Room is always main-safe

i believe you - but is there any documentation showing this to show my co-workers?

SQLDelight, for now, unfortunately, the answer depends on what you do. I wish that, at least in development mode, it'd throw by default if you try run on an app's main thread that is not in JS.

actually I think i found the code for Room https://android.googlesource.com/platform/frameworks/support/+/refs/heads/androidx-platfo[…]p/room/ktx/src/main/java/androidx/room/CoroutinesRoom.kt

I would say that general rule, that any suspend function must be “main-safe” aka non blocking. If some library exposes suspend function which is blocking, it’s 100% bug of the library and should be reported

FYI Room has its own Architecture Components IO dispatcher which is specialized for Room operations. You don't need to switch dispatchers.

Room will use different Dispatchers for transactions and queries. These are derived from the executors you provide when building your Database or by default will use the Architecture Components IO executor. This is the same executor that would be used by LiveData to do background work.

https://medium.com/androiddevelopers/room-coroutines-422b786dc4c5

I wrote about it here: https://www.lukaslechner.com/do-i-need-to-call-suspend-functions-of-retrofit-and-room-on-a-background-thread/

perfect to share those with my co-workers and for me to read over. thanks!!