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>

2 files changed, 48 insertions, 0 deletions

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