Add terraform-lsp integration (#2758)

* Add terraform-lsp integration

https://github.com/juliosueiras/terraform-lsp

* Add tests & docs for terraform-lsp integration

terraform_langserver_options setting added to send custom flags to
terraform-lsp.

Vader tests have been added to test custom executable, custom flags, and
finding the project root. All tests pass.

Initial documentation has been added for the above.

Resolves dense-analysis/ale#2758, juliosueiras#57

* Fix tag alignment

Co-authored-by: = <Aubrey.S.Lavigne@gmail.com>
Co-authored-by: w0rp <w0rp@users.noreply.github.com>

5 files changed, 93 insertions, 0 deletions

diff --git a/ale_linters/terraform/terraform_lsp.vim b/ale_linters/terraform/terraform_lsp.vim
new file mode 100644
index 00000000..e2408c15
--- /dev/null
+++ b/ale_linters/terraform/terraform_lsp.vim
@@ -0,0 +1,25 @@
+" Author: OJFord <dev@ojford.com>
+" Description: terraform-lsp integration for ALE (cf. https://github.com/juliosueiras/terraform-lsp)
+
+call ale#Set('terraform_langserver_executable', 'terraform-lsp')
+call ale#Set('terraform_langserver_options', '')
+
+function! ale_linters#terraform#terraform_lsp#GetCommand(buffer) abort
+    return '%e'
+    \   . ale#Pad(ale#Var(a:buffer, 'terraform_langserver_options'))
+endfunction
+
+function! ale_linters#terraform#terraform_lsp#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_lsp',
+\   'lsp': 'stdio',
+\   'executable': {b -> ale#Var(b, 'terraform_langserver_executable')},
+\   'command': function('ale_linters#terraform#terraform_lsp#GetCommand'),
+\   'project_root': function('ale_linters#terraform#terraform_lsp#GetProjectRoot'),
+\   'language': 'terraform',
+\})
diff --git a/doc/ale-terraform.txt b/doc/ale-terraform.txt
index 387fd732..f62db190 100644
--- a/doc/ale-terraform.txt
+++ b/doc/ale-terraform.txt
@@ -33,6 +33,25 @@ g:ale_terraform_terraform_executable     *g:ale_terraform_terraform_executable*
 
 
 ===============================================================================
+terraform-lsp                                     *ale-terraform-terraform-lsp*
+
+g:ale_terraform_langserver_executable   *g:ale_terraform_langserver_executable*
+                                        *b:ale_terraform_langserver_executable*
+  Type: |String|
+  Default: `'terraform-lsp'`
+
+  This variable can be changed to use a different executable for terraform-lsp.
+
+
+g:ale_terraform_langserver_options         *g:ale_terraform_langserver_options*
+                                           *b:ale_terraform_langserver_options*
+  Type: |String|
+  Default: `''`
+
+  This variable can be changed to pass custom CLI flags to terraform-lsp.
+
+
+===============================================================================
 tflint                                                   *ale-terraform-tflint*
 
 g:ale_terraform_tflint_executable           *g:ale_terraform_tflint_executable*
diff --git a/doc/ale.txt b/doc/ale.txt
index 469fa106..81212029 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -2623,6 +2623,7 @@ documented in additional help files.
   terraform...............................|ale-terraform-options|
     terraform-fmt-fixer...................|ale-terraform-fmt-fixer|
     terraform.............................|ale-terraform-terraform|
+    terraform-lsp.........................|ale-terraform-terraform-lsp|
     tflint................................|ale-terraform-tflint|
   tex.....................................|ale-tex-options|
     chktex................................|ale-tex-chktex|
diff --git a/test/command_callback/test_terraform_lsp_command_callback.vader b/test/command_callback/test_terraform_lsp_command_callback.vader
new file mode 100644
index 00000000..7a491d54
--- /dev/null
+++ b/test/command_callback/test_terraform_lsp_command_callback.vader
@@ -0,0 +1,48 @@
+Before:
+  call ale#assert#SetUpLinterTest('terraform', 'terraform_lsp')
+
+After:
+  if isdirectory(g:dir . '/.terraform')
+    call delete(g:dir . '/.terraform', 'd')
+  endif
+
+  unlet! b:ale_terraform_langserver_executable
+  unlet! b:ale_terraform_langserver_options
+
+  call ale#assert#TearDownLinterTest()
+
+Execute(Should send correct LSP language):
+  AssertLSPLanguage 'terraform'
+
+Execute(Should load default executable):
+  AssertLinter 'terraform-lsp', ale#Escape('terraform-lsp')
+
+Execute(Should configure custom executable):
+  let b:ale_terraform_langserver_executable = 'foo'
+  AssertLinter 'foo', ale#Escape('foo')
+
+Execute(Should set custom options):
+  let b:ale_terraform_langserver_options = '--bar'
+
+  AssertLinter 'terraform-lsp',
+  \ ale#Escape('terraform-lsp') . ' --bar'
+
+Execute(Should return current directory if it contains .terraform directory):
+  call mkdir(g:dir . '/.terraform')
+  AssertLSPProject g:dir
+
+Execute(Should return nearest directory with .terraform if found in parent directory):
+  call ale#test#SetFilename('../terraform_files/main.tf')
+
+  let b:parent_dir = ale#path#Simplify(g:dir . '/..')
+  let b:tf_dir = b:parent_dir . '/.terraform'
+
+  if !isdirectory(b:tf_dir)
+    call mkdir(b:tf_dir)
+  endif
+
+  AssertLSPProject b:parent_dir
+
+  call delete(b:tf_dir, 'd')
+  unlet!b:parent_dir
+  unlet!b:tf_dir
diff --git a/test/terraform_files/main.tf b/test/terraform_files/main.tf
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/terraform_files/main.tf