I think there's more in common than you give credit for.
What is the fundamental difference between a 'method call' and a 'message pass'?
In both scenarios, you can be synchronous or asynchronous, blocking or non-blocking, remain on one thread (technically 2 if it's across a network) or fork out into multiple threads. You can wait for a result, or you can fire-and-forget (void). A networking problem is just another kind of Exception.
Even in a typical microservice codebase, it's not immediately apparent from reading the code whether userService.createUser() will call across a network, or just into another class.
The only fundamental difference I can think of right now is that in a non-networked system, you can be pretty sure your static typing holds for the whole program, whereas in a networked system, your types might drift between versions.
I think the similarity is more like a mathematical/structural one, and doesn’t hold much water in a pragmatic sense. The possible error conditions for a network call are just insanely bigger than of a function call.
Also, Smalltalk and alia of the “real OOP” kind has some extremes with regards to messaging, like the number 3 being told to increase itself by one, which would not be done this way in today’s OOP languages and not just for performance reasons.
Method calls are more of a degenerate case of a distributed system, which is significantly easier to reason about.
What is the fundamental difference between a 'method call' and a 'message pass'?
In both scenarios, you can be synchronous or asynchronous, blocking or non-blocking, remain on one thread (technically 2 if it's across a network) or fork out into multiple threads. You can wait for a result, or you can fire-and-forget (void). A networking problem is just another kind of Exception.
Even in a typical microservice codebase, it's not immediately apparent from reading the code whether userService.createUser() will call across a network, or just into another class.
The only fundamental difference I can think of right now is that in a non-networked system, you can be pretty sure your static typing holds for the whole program, whereas in a networked system, your types might drift between versions.
But again, more similarities than differences.