Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

3.29.0

Plugin version

No response

Node.js version

16.15.0

Operating system

macOS

Operating system version (i.e. 20.04, 11.3, 10)

12.3.1

Description

When I set an error handler on a Fastify instance after registering a plugin within an awaited statement, the error handler does not work as expected.

An example scenario: Let f be a Fastify instance.

• Add a / get handler on instance f that throws an error.
• Register a plugin on instance f with any prefix (e.g., /bar) with an await keyword.
• Set error handler (call it h) on instance f.

When fetching / on this instance, an error is thrown and h is expected to run. However, it does not. The default handler is run instead.

Removing the await keyword fixes this issue. But the existence of the await keyword or the nonexistence thereof should not alter any behavior--unless there is an intricacy in this situation that forces such behavior.

Steps to Reproduce

A reproduction of the issue can be found here:
https://github.com/omothm/fastify-error-handler-await-repro

Expected Behavior

All 3 test scenarios in the reproduction repo are expected to pass. Currently, one scenario fails (the one with await instance.register()) but was expected to pass.