Dockerfile syntax - How to use ARG for Windows image

Question

I have the following docker file which downloads different things base on an argument passed in from docker-compose (either 2019 or 2022)

FROM mcr.microsoft.com/windows/servercore:ltsc2022

ARG VSVersion

SHELL ["powershell", "-Command", "$ErrorActionPreference = 'Stop'; $ProgressPreference = 'SilentlyContinue';"]
WORKDIR /Temp

SHELL ["cmd", "/S", "/C"]

RUN if [ "$VSVersion" == "2019" ]; then `
    curl -SL --output vs_buildtools.exe https://aka.ms/vs/16/release/vs_buildtools.exe...

My issue is, the conditional run command is not working - it doesn't install in the above syntax.

I also tried using "%VSVersion%"=="2019" because it's default windows shell, but I get error: "2019"=="2019" was unexpected at this time .

Could someone please point me towards the right syntax because I've tried various combinations, with and without quotations, to no avail...

thanks

Answer 1

Dockerfile is in windows shell not bash, so change the if statement syntax to batch instead of bash:

RUN if "%VSVersion%"=="2019"( `
# Download the Build Tools bootstrapper.
curl -SL --output vs_buildtools.exe.. )