How to tag docker image with docker-compose

Question

I want to build image via docker-compose and set specific tag to it. Documentation says:

Compose will build and tag it with a generated name, and use

Answer 1

If you specify image as well as build, then Compose names the built image with the webapp and optional tag specified in image:

build: ./dir
image: webapp:tag

This results in an image named webapp and tagged tag, built from ./dir.

https://docs.docker.com/compose/compose-file/#build