ocamllsp: add support for the dune filetype (#1884)

* ocamllsp: add dune as supported language

ocaml-lsp-server-1.11.3 enables 'dune' rpc integration
(you need a running `dune build --watch` command which provides the RPC
server).
This allows to reformat `dune` files, and to see `dune` and other build
errors as soon as you change a file (e.g. quite useful on newly created
files which would otherwise show an LSP error until first build).

Signed-off-by: Edwin Török <edwin@etorok.net>

* ocamllsp: dune-project and dune-workspace also mark roots

Although most dune projects will also have a *.opam file,
this file might be generated by the build system.
Newer versions of dune have a dune-project file to mark the root though,
and users can create a dune-workspace file as well.

Note that `dune` files themselves do NOT mark the root: they can be
present in subdirs too.

The rules on how `dune` itself finds the root are documented here:
https://dune.readthedocs.io/en/stable/usage.html#finding-the-root
"The root of the current workspace is determined by looking up a
dune-workspace or dune-project file in the current directory and its
parent directories. Dune requires at least one of these two files to
operate."

Signed-off-by: Edwin Török <edwin@etorok.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/lua/lspconfig/server_configurations/ocamllsp.lua b/lua/lspconfig/server_configurations/ocamllsp.lua
index 15284716..6cff66b6 100644
--- a/lua/lspconfig/server_configurations/ocamllsp.lua
+++ b/lua/lspconfig/server_configurations/ocamllsp.lua
@@ -6,6 +6,7 @@ local language_id_of = {
   ocamlinterface = 'ocaml.interface',
   ocamllex = 'ocaml.ocamllex',
   reason = 'reason',
+  dune = 'dune'
 }
 
 local get_language_id = function(_, ftype)
@@ -15,8 +16,8 @@ end
 return {
   default_config = {
     cmd = { 'ocamllsp' },
-    filetypes = { 'ocaml', 'ocaml.menhir', 'ocaml.interface', 'ocaml.ocamllex', 'reason' },
-    root_dir = util.root_pattern('*.opam', 'esy.json', 'package.json', '.git'),
+    filetypes = { 'ocaml', 'ocaml.menhir', 'ocaml.interface', 'ocaml.ocamllex', 'reason', 'dune' },
+    root_dir = util.root_pattern('*.opam', 'esy.json', 'package.json', '.git', 'dune-project', 'dune-workspace'),
     get_language_id = get_language_id,
   },
   docs = {
@@ -32,7 +33,7 @@ opam install ocaml-lsp-server
 ```
     ]],
     default_config = {
-      root_dir = [[root_pattern("*.opam", "esy.json", "package.json", ".git")]],
+      root_dir = [[root_pattern("*.opam", "esy.json", "package.json", ".git", "dune-project", "dune-workspace")]],
     },
   },
 }