Conditional COPY/ADD in Dockerfile?

Question

Inside of my Dockerfiles I would like to COPY a file into my image if it exists, the requirements.txt file for pip seems like a good candidate but how would this be achieved

Answer 1

As stated by this comment, Santhosh Hirekerur's answer still copies the file, to archive a true conditional copy, you can use this method.

ARG BUILD_ENV=copy

FROM alpine as build_copy
ONBUILD COPY file /file

FROM alpine as build_no_copy
ONBUILD RUN echo "I don't copy"

FROM build_${BUILD_ENV}
# other stuff

The ONBUILD instructions ensures that the file is only copied if the "branch" is selected by the BUILD_ENV. Set this var using a little script before calling docker build