Fix 3371 - Add terraform-ls support

ale_linters/terraform/terraform_ls.vim

@@ -0,0 +1,38 @@
+" Author: Horacio Sanson <hsanson@gmail.com>
+" Description: terraform-ls integration for ALE (cf. https://github.com/hashicorp/terraform-ls)
+
+call ale#Set('terraform_terraform_executable', 'terraform')
+call ale#Set('terraform_ls_executable', 'terraform-ls')
+call ale#Set('terraform_ls_options', '')
+
+function! ale_linters#terraform#terraform_ls#GetTerraformExecutable(buffer) abort
+    let l:terraform_executable = ale#Var(a:buffer, 'terraform_terraform_executable')
+
+    if(ale#path#IsAbsolute(l:terraform_executable))
+        return '-tf-exec ' . l:terraform_executable
+    endif
+
+    return ''
+endfunction
+
+function! ale_linters#terraform#terraform_ls#GetCommand(buffer) abort
+    return '%e'
+    \ . ale#Pad('serve')
+    \ . ale#Pad(ale_linters#terraform#terraform_ls#GetTerraformExecutable(a:buffer))
+    \ . ale#Pad(ale#Var(a:buffer, 'terraform_ls_options'))
+endfunction
+
+function! ale_linters#terraform#terraform_ls#GetProjectRoot(buffer) abort
+    let l:tf_dir = ale#path#FindNearestDirectory(a:buffer, '.terraform')
+
+    return !empty(l:tf_dir) ? fnamemodify(l:tf_dir, ':h:h') : ''
+endfunction
+
+call ale#linter#Define('terraform', {
+\   'name': 'terraform_ls',
+\   'lsp': 'stdio',
+\   'executable': {b -> ale#Var(b, 'terraform_ls_executable')},
+\   'command': function('ale_linters#terraform#terraform_ls#GetCommand'),
+\   'project_root': function('ale_linters#terraform#terraform_ls#GetProjectRoot'),
+\   'language': 'terraform',
+\})