Add rnix-lsp for Nix diagnostics and completion

ale_linters/nix/rnix_lsp.vim

@@ -0,0 +1,16 @@
+" Author: jD91mZM2 <me@krake.one>
+" Description: rnix-lsp language client
+
+function! ale_linters#nix#rnix_lsp#GetProjectRoot(buffer) abort
+    " rnix-lsp does not yet use the project root, so getting it right is not
+    " important
+    return fnamemodify(a:buffer, ':h')
+endfunction
+
+call ale#linter#Define('nix', {
+\   'name': 'rnix_lsp',
+\   'lsp': 'stdio',
+\   'executable': 'rnix-lsp',
+\   'command': '%e',
+\   'project_root': function('ale_linters#nix#rnix_lsp#GetProjectRoot'),
+\})

doc/ale-supported-languages-and-tools.txt

@@ -304,6 +304,7 @@ Notes:
 * nix
   * `nix-instantiate`
   * `nixpkgs-fmt`
+  * `rnix-lsp`
 * nroff
   * `alex`!!
   * `proselint`

supported-tools.md

@@ -313,6 +313,7 @@ formatting.
 * nix
   * [nix-instantiate](http://nixos.org/nix/manual/#sec-nix-instantiate)
   * [nixpkgs-fmt](https://github.com/nix-community/nixpkgs-fmt)
+  * [rnix-lsp](https://github.com/nix-community/rnix-lsp)
 * nroff
   * [alex](https://github.com/wooorm/alex) :floppy_disk:
   * [proselint](http://proselint.com/)

test/nix/test_rnix_lsp.vader

@@ -0,0 +1,14 @@
+" Author: jD91mZM2 <me@krake.one>
+" Description: Tests for rnix-lsp language client
+
+Before:
+  call ale#assert#SetUpLinterTest('nix', 'rnix_lsp')
+
+After:
+  call ale#assert#TearDownLinterTest()
+
+Execute(should start rnix-lsp):
+  call ale#test#SetFilename('./test.nix')
+  AssertLSPLanguage 'nix'
+  AssertLSPOptions {}
+  AssertLSPProject ale#path#Simplify('.')