FROM ... AS <name> clarification

[shealen-greencitizen]

Is this a docs issue?

• My issue is about the documentation content or website

Type of issue

Clarification

Description

The last line of the following example snippet may confuse some beginners:

FROM ubuntu AS base
RUN apt-get update && apt-get install -y shared-tooling

FROM base AS dev
RUN apt-get install -y dev-tooling

FROM base AS prod
COPY --from=build /app /app

as there is no named build stage in the snippet. I understand that it can merely be assumed such a stage exists, but since the prod stage is built from the base base image, it takes a second to comprehend there were merely omitted steps.

Location

https://docs.docker.com/reference/dockerfile/

Suggestion

Although a bit more verbose, it would perhaps be clearer to have something along the lines of:

FROM ubuntu AS base
RUN apt-get update && apt-get install -y shared-tooling
RUN mkdir /app && touch base.txt

FROM base AS dev
RUN apt-get install -y dev-tooling

FROM base AS prod
COPY --from=base /app /app

in which everything is explicit.