DocumenterMarkdown
The MadsPublish.jl imports DocumenterMarkdown, though it seems it doesn't use it. It generates the output in HTML format, which is already covered by format=Documenter.Writers.HTMLWriter; the DocumentedMarkdown allows generating Markdown output using format=DocumenterMarkdown.Markdown, which isn't used.
This wouldn't be a problem except that DocumenterMarkdown only works with pre-1.0 versions of Documenter, so installing Mads forces Documenter to an old version (0.27.25), which has an incompatible API with the 1.* Documenter versions, breaking anything that is using the latest (presumably stable?) Documenter 1.* API.
It also wouldn't have been a problem if DocumenterMarkdown was being updated, but according to https://github.com/JuliaDocs/DocumenterMarkdown.jl/issues/11 it doesn't seem like this would be any time soon.
How about simply removing DocumenterMarkdown as a dependency of Mads?
FYI there is JuliaDocs/DocumenterMarkdown#13 which will transition DocumenterMarkdown to v1 of Documenter. That should happen sometime this month.
Ugh, missed it. My bad.
Still - if DocumenterMarkdown isn't ever used, why make it a dependency and import it in the 1st place? Or am I missing something additional?
DocumenterMarkdown has been removed. I agree with your comments. We are working to compertamentalize the packages.