KotlinNullPointerException when api call returns 204 No Content with null response about eithernet HOT 4 CLOSED

This is a tricky case. I think we should try to support 204 responses in the future, but cannot right now for two reasons:

1. We can't tell that your BlockDto? type is nullable from java reflection alone (which is what retrofit uses)
2. Retrofit does not try converters for 204/205 response codes - square/retrofit#2867

The second one requires addressing in Retrofit, because we are just passing on the body from retrofit directly back to it and it throws the KNPE on its own null response body. It only natively supports null response bodies for Void and Unit (where it ignores them), so you could file a feature request upstream to support nullable types somehow. Fair warning though that is likely not possible right now due to the first mentioned bullet. It would require either reading @Nullable type annotations or some degree of kotlin-reflect or kotlin metadata to properly parse the kotlin function signature.

You should either use Unit or change your API to use something other than 204/205 for now.

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Adding to this a bit more - you should follow this issue square/retrofit#3075

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So currently there's no way we can handle 204 No content return type ?

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As explained at length in the comment above, no.

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