docker/README.md mistakenly claims an argument is necessary

[MarkCallow]

In its Building Dockerfile section, docker/README.md says

---

This image requires to specify following build arguments:

arg	description
EMSCRIPTEN_VERSION	One of released version of Emscripten. For example 1.39.17 Minimal supported version is 1.39.0

---

and gives the example

# using docker
docker build \
    --network host \
    --build-arg=EMSCRIPTEN_VERSION=1.39.17 \
    -t emscripten/emsdk:1.39.17 \
    -f docker/Dockerfile \
    .

The argument appears to be optional not required. This build succeeds.

# using docker
docker build \
    --network host \
    -t emscripten/emsdk \
    -f docker/Dockerfile \
    .

Furthermore if you build in the described way, the run example will fail because when you use just emscripten/emsdk as the image name, as the example does, docker will report ``emscripten/emsdk:latest not found`.

I do not know the correct fix so have not attempted to create a PR.

[kleisauke]

The Docker image is built against the tip-of-tree build of Emscripten when the EMSCRIPTEN_VERSION build argument is not specified, see:

emsdk/docker/Dockerfile

Line 3 in 1fe8067

ARG EMSCRIPTEN_VERSION=tot

So we could rephrase that sentence to include that information. I'm not sure about that second issue, maybe the locally built image conflicts with the image from Docker hub?

[MarkCallow]

So we could rephrase that sentence to include that information.

Yes. This is what I have in mind. I just didn't know the correct phrasing. You've now explained it.

I'm not sure about that second issue

I miswrote. What happens when I try the run example from README.md is that docker tells me it can't find emscripten/emsdk:latest locally and then downloads it from docker.com. This will not be an issue with suitable rephrasing of the EMSCRIPTEN_VERSION explanation.

[trzecieu]

Hello! Yes, you're right about that. I've created a small tweak proposal to the documentation.