[Solved] Do I have to call return true each time I use onMessage.addListener responseCallback?

Question

This is the expected behavior and clearly stated in the documentation:

This function [sendResponse] becomes invalid when the event listener returns, unless you return true from the event listener to indicate you wish to send a response asynchronously (this will keep the message channel open to the other end until sendResponse is called).

Your function updateMirrors is apparently asynchronous: the callback function does not get executed immediately but is sent into a queue. So, you’re not returning true “after” its execution, you are actually hitting return true before sendResponse.

Therefore, it’s necessary to tell Chrome “expect an answer later”.

Accepted Answer

This is the expected behavior and clearly stated in the documentation:

This function [sendResponse] becomes invalid when the event listener returns, unless you return true from the event listener to indicate you wish to send a response asynchronously (this will keep the message channel open to the other end until sendResponse is called).

Your function updateMirrors is apparently asynchronous: the callback function does not get executed immediately but is sent into a queue. So, you’re not returning true “after” its execution, you are actually hitting return true before sendResponse.

Therefore, it’s necessary to tell Chrome “expect an answer later”.