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+#+TITLE: Neovim, OCaml Interfaces, Tree-Sitter and LSP
+
+Can we all agree that witnessing syntax highlighting being absolutely off is
+probably the most annoying thing that can happen to anybody?
+
+I mean, just look at this horror.
+
+#+CAPTION: Syntax highlighting being absolutely wrong
+#+NAME:    fig:wrong-highlingting
+[[../img/wrong-highlighting.png]]
+
+What you are looking at is the result of trying to enable ~tree-sitter~ for
+OCaml hacking and calling it a day. In a nutshell, OCaml ~mli~ files are
+quickly turning into a random mess of nonsensical colors, and I didn’t know
+why. I tried to blame
+[[https://github.com/tree-sitter/tree-sitter-ocaml/issues/72][~tree-sitter-ocaml~]],
+but of course I was wrong.
+
+The issue is subtle, and to be honest, I don’t know if I totally grasp it. But
+from my rough understanding, it breaks down as follows.
+
+- ~tree-sitter-ocaml~ defines two grammars: ~ocaml~ for the ~ml~ files, and
+  ~ocaml_interface~ (but ~ocamlinterface~ also works) for the ~mli~ files
+- By default, neovim uses the filetype ~ocaml~ for ~mli~ files, so the incorrect
+  parser is being used for syntax highlighting. This explains the root issue
+- Bonus: ~ocamllsp~ does not recognize the ~ocamlinterface~ filetype by
+  default (but somehow use the ~ocaml.interface~ id for ~mli~ files…[fn::There
+  is probably something to be done here.])
+
+So, in order to have both ~tree-sitter~ and ~ocamllsp~ working at the same time,
+I had to tweak my configuration a little bit.
+
+#+begin_src lua
+lspconfig.ocamllsp.setup({
+  cmd = { 'ocamllsp', '--fallback-read-dot-merlin' },
+  -- Necessary to get tree sitter to work with .mli files
+  filetypes = vim.list_extend(
+    require('lspconfig.server_configurations.ocamllsp')
+      .default_config
+      .filetypes,
+    { 'ocamlinterface' }
+  ),
+})
+
+vim.cmd([[au! BufNewFile,BufRead *.mli setfiletype ocamlinterface]])
+#+end_src
+
+And now, I am blessed with a consistent syntax highlighting for my ~mli~ files.
+
+#+CAPTION: Syntax highlighting being absolutely wrong
+#+NAME:    fig:wrong-highlingting
+[[../img/good-highlighting.png]]