Currently when generating docs with dune (dune build @doc) the generated HTML uses the highlight.pack.js javascript library for syntax highlighting. This script is copied to _build/default/_doc/_html/ along with odoc.css by the odoc/assets.ml/write function.

For some reason the second, and all consecutive builds, remove the highlight.pack.js file.

To reproduce run the following in any dune-managed package:

$ dune clean
$ dune build @doc
$ ls _build/default/_doc/_html/
highlight.pack.js  index.html  odoc.css  <package>
$ dune build @doc
$ ls _build/default/_doc/_html/
index.html  odoc.css  <package>        # <-- highlight.pack.js is missing

I find this strange because both the css and the javascript files seem to be handled equally in odoc, but only the javascript file disappears.