Add Support for Fastify v5.x in @nestjs/mercurius

[carlos-alex]

Is there an existing issue that is already proposing this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe it

I’m facing a compatibility issue with @nestjs/mercurius due to its peer dependency restriction on Fastify ^4.12.0. As Fastify v4.x is no longer actively maintained, and Fastify v5.x is the latest stable version, this creates challenges for projects that need to use modern and supported dependencies.

Details
Current Behavior:
The installation of @nestjs/mercurius results in a peer dependency warning when using Fastify 4.29.x or 5.x.
Example warning:

npm WARN Could not resolve dependency:
npm WARN peer fastify@"^4.12.0" from @nestjs/[email protected]

Describe the solution you'd like

@nestjs/mercurius should support Fastify v5.x to enable users to benefit from the latest features and fixes.

Teachability, documentation, adoption, migration strategy

No response

What is the motivation / use case for changing the behavior?

Please update @nestjs/mercurius to support Fastify v5.x as a peer dependency. This will allow projects to stay up-to-date with maintained versions of Fastify and avoid compatibility issues.

Environment
@nestjs/mercurius: 12.2.2
Fastify: 4.29.0 / 5.1.0
Node.js: v22.12.0

Thank you for your excellent work on these tools! Let me know if you need more details to investigate this issue further.

[Tony133]

see PR here: #3407

[carlos-alex]

ok! nice!

[kamilmysliwiec]

nestjs/nest#14177