2.18 regression: errors out with empty SERVER_FALLBACK_PAGE

[OdyX]

Describe the bug
With the following Dockerfile, I could run the resulting image even with an empty SERVER_FALLBACK_PAGE:

ARG STATIC_WEB_SERVER_VERSION=2.17
FROM joseluisq/static-web-server:${STATIC_WEB_SERVER_VERSION}

# SWS configuration, check https://sws.joseluisq.net/configuration/environment-variables/
ENV SERVER_ROOT=/public

# Set fallback page for Single-page Applications
ARG SERVER_FALLBACK_PAGE
ENV SERVER_FALLBACK_PAGE=${SERVER_FALLBACK_PAGE}

# The whole website
COPY public/ /public/

Now, setting STATIC_WEB_SERVER_VERSION to 2.18, the same build gives:

error: a value is required for '--page-fallback <PAGE_FALLBACK>' but none was supplied

To Reproduce
Set an empty SERVER_FALLBACK_PAGE environment variable:

# Works
$ docker run -e SERVER_FALLBACK_PAGE= joseluisq/static-web-server:2.17
^C
# Fails
$ docker run -e SERVER_FALLBACK_PAGE= joseluisq/static-web-server:2.18
error: a value is required for '--page-fallback <PAGE_FALLBACK>' but none was supplied

For more information, try '--help'.

Environment and Specs

• static-web-server: 2.18

This seems to be a regression caused by #215

[joseluisq]

Thanks for that!
We will fix that definitely, in fact, will be trivial to be fixed.
But for now, the "workaround" should be to unset the SERVER_FALLBACK_PAGE and avoid passing it to SWS if empty.

[OdyX]

In fact, I've found that I can pass false to it too;

ARG STATIC_WEB_SERVER_VERSION=2.18
FROM joseluisq/static-web-server:${STATIC_WEB_SERVER_VERSION}

# SWS configuration, check https://sws.joseluisq.net/configuration/environment-variables/
ENV SERVER_ROOT=/public

# Set fallback page for Single-page Applications
ARG SERVER_FALLBACK_PAGE=false
ENV SERVER_FALLBACK_PAGE=${SERVER_FALLBACK_PAGE}

# The whole website
COPY public/ /public/

This is thanks to https://docs.rs/clap/latest/clap/struct.Arg.html#method.env:

Note that the value parser controls how flags are parsed. In this case we’ve selected FalseyValueParser. A false literal is n, no, f, false, off or 0. An absent environment variable will also be considered as false. Anything else will considered as true.

[joseluisq]

In fact, I've found that I can pass false to it too;

You can theoretically whatever string that Pathbuf supports. But it will get validated when trying to read the fallback page content at server start-up time.

This is thanks to https://docs.rs/clap/latest/clap/struct.Arg.html#method.env:

Note that the value parser controls how flags are parsed. In this case we’ve selected FalseyValueParser. A false literal is n, no, f, false, off or 0. An absent environment variable will also be considered as false. Anything else will considered as true.

Yeah, this is a rigid effect of our last migration to Clap v4.
Anyway, this is fixed now. See more details on PR #219.

[joseluisq]

You can use the devel Docker images to test the bugfix.

docker pull joseluisq/static-web-server:devel
docker pull joseluisq/static-web-server:devel-alpine

[joseluisq]

Fixed on v2.19.0