I have released tiny-ssg, an unopinionated static site generator in Node.js with a tiny API that is friendly with hot reloaded modules (e.g. with invalidate-module).
The API is very small; these are its methods: new SSG(), ssg.manifest(),
ssg.build(), and ssg.dryRun().
It is very unopinionated, in otherwords there are no conventions. I don't tell
you where you need to put your files or what file formats work with it. The only
responsibility of tiny-ssg is that it will write out the pages defined by
manifest() at the correct location on disk. Everything else, such as
transforming files (e.g. markdown to html) is done by you, the programmer. Used
with the plethora of tools on npm, it truly is a bring-your-own-conventions
type of static site generator.
It works nicely with watchers like chokidar and invalidate-module in
that if build() is called again within the same process, it will automatically
remove files that are no longer returned from manifest() and rebuild the
entire site. With invalidate-module, one can use React components as the layout
engine and can iterate quickly without quitting the Node.js process.
I developed tiny-ssg because I really didn't like the way that I was generating this blog previously, as written about in an earlier blog post of mine. Looking back, I think that code was too imperative for my tastes. The build process was something like, "first read the posts directory, then convert these posts into html in memory, then build the post pages and the index, then build the rest of the pages." There was no central location to see all the urls of the final site.
With tiny-ssg, you can see all the urls in a central location in the callback of
manifest(). In a way, this is more declarative. It says, "here's a list of
pages at these urls, go build them."
Check out the source of this blog which is now built with tiny-ssg. I would
start with build.js which shows the manifest() call. The non-trivial
part is a call to fs.readdir() on the posts directory that will eventually be
used to generate each post, the index, and feed pages.
Please refer to the README of tiny-ssg for how to get started and for examples involving markdown and React.