I recently updated my MikTeX distribution (The new interface is really nice by the way, Thank You to the contributors/developers) and I got curious about the path resolution of files when compiling a document.
I have an experimental TikZ package that I've been fiddling with for a while. It's notihing fancy it simply defines a base length, that defaults to 1 em, and allows me to set this value to something else during the compilation of the document. I use this to draw a set of tikz pics, also provided by the package, to a consistent scale.
Initially I was linking the files the package produces, *.code.tex and *.sty files, directly into MikTeX's TeXMF tree, using the mklink function available under windows 10. That is I was placing these files under MikTeX/TeXMF/tex/generic/pgf{/libraries,/libraries/shapes,/fronendlayer/tikz/libraries}.
I have now setup a local TeXMF tree which I'm populating instead; this resides next to my source code and I can simply copy the files across. That is I am now copying these files to LOCAL/TeXMF/tex/generic/pgf{/libraries,/libraries/shapes,/fronendlayer/tikz/libraries} and have added LOCAL/TeXMF as an additional directory for MikTeX to scan under Settings>Directories>Paths and I include this path before the MikTeX one.
Now I'm unsure if the paths under the local tree are masking or conflicting with those in the MikTeX one or not, it seems a possiblity. That is does LOCAL/TeXMF/tex/some/path/ block MikTeX/TeXMF/tex/some/path/ at all ?
Background
The reason for the question is that I'm not sure if I broke my installation or not or if I simply updated to an intermediate version of PGF from MikTeX and need to simply wait a week for the next patch. LuaLaTeX started reporting the following error shortly after I updated my system and migrated my experimental package; I did both at the same time and I'm not sure if this is my fault or not.
! Package pgf Error: Graph drawing library 'force' not found.
See the pgf package documentation for explanation.
Type H <return> for immediate help.
...
Googling about takes one to this question which links to Github and finally SourceForge. The issue it seems has been reported and fixed and I suspect there is a bit of lead time to wait before MikTeX gets and distributes the update. So on the PGF side it looks all hunky dory which leads me to think that migrating my package broke the graphdrawing look up of LuaLaTeX but I'm not sure.