Update project root detection for erlang_ls linter (#4619)

* Refactor erlang_ls linter tests

* Add Rebar3 _checkouts support for erlang_ls linter

* Add Erlang.mk support for erlang_ls linter

ale_linters/erlang/erlang_ls.vim

@@ -21,7 +21,14 @@ function! s:GetCommand(buffer) abort
 endfunction
 
 function! s:FindProjectRoot(buffer) abort
-    let l:markers = ['_build/', 'erlang_ls.config', 'rebar.lock']
+    let l:markers = [
+    \   '_checkouts/',
+    \   '_build/',
+    \   'deps/',
+    \   'erlang_ls.config',
+    \   'rebar.lock',
+    \   'erlang.mk',
+    \]
 
     " This is a way to find Erlang/OTP root (the one that is managed
     " by kerl or asdf).  Useful if :ALEGoToDefinition takes us there.

test/linter/test_erlang_erlang_ls.vader

@@ -1,8 +1,9 @@
 Before:
-  let b:files = '../test-files/erlang'
   call ale#assert#SetUpLinterTest('erlang', 'erlang_ls')
 
 After:
+  unlet! b:root
+
   call ale#assert#TearDownLinterTest()
 
 Execute(The default command should be correct):
@@ -30,19 +31,40 @@ Execute(Log directory should be configurable):
   \ . ' --log-level=' . ale#Escape('info')
 
 Execute(Project root should be detected using erlang_ls.config):
-  call ale#test#SetFilename(b:files . '/app_with_erlang_ls_config/src/app.erl')
-  AssertLSPProject ale#test#GetFilename(b:files . '/app_with_erlang_ls_config')
+  let b:root = '../test-files/erlang/app_with_erlang_ls_config'
 
-  call ale#test#SetFilename(b:files . '/app_with_erlang_ls_config/_build/default/lib/dep/src/dep.erl')
-  AssertLSPProject ale#test#GetFilename(b:files . '/app_with_erlang_ls_config')
+  call ale#test#SetFilename(b:root . '/src/app.erl')
+  AssertLSPProject ale#test#GetFilename(b:root)
+
+  call ale#test#SetFilename(b:root . '/_build/default/lib/dep/src/dep.erl')
+  AssertLSPProject ale#test#GetFilename(b:root)
+
+  call ale#test#SetFilename(b:root . '/deps/dep/src/dep.erl')
+  AssertLSPProject ale#test#GetFilename(b:root)
 
 Execute(Root of Rebar3 project should be detected):
-  call ale#test#SetFilename(b:files . '/app/src/app.erl')
-  AssertLSPProject ale#test#GetFilename(b:files . '/app')
+  let b:root = '../test-files/erlang/rebar3_app'
 
-  call ale#test#SetFilename(b:files . '/app/_build/default/lib/dep/src/dep.erl')
-  AssertLSPProject ale#test#GetFilename(b:files . '/app')
+  call ale#test#SetFilename(b:root . '/src/app.erl')
+  AssertLSPProject ale#test#GetFilename(b:root)
+
+  call ale#test#SetFilename(b:root . '/_build/default/lib/dep/src/dep.erl')
+  AssertLSPProject ale#test#GetFilename(b:root)
+
+  call ale#test#SetFilename(b:root . '/_checkouts/dep/src/dep.erl')
+  AssertLSPProject ale#test#GetFilename(b:root)
+
+Execute(Root of Erlang.mk project should be detected):
+  let b:root = '../test-files/erlang/erlang_mk_app'
+
+  call ale#test#SetFilename(b:root . '/src/app.erl')
+  AssertLSPProject ale#test#GetFilename(b:root)
+
+  call ale#test#SetFilename(b:root . '/deps/dep/src/dep.erl')
+  AssertLSPProject ale#test#GetFilename(b:root)
 
 Execute(Root of kerl managed Erlang/OTP installation should be detected):
-  call ale#test#SetFilename(b:files . '/kerl_otp_root/lib/stdlib-4.1.1/array.erl')
-  AssertLSPProject ale#test#GetFilename(b:files . '/kerl_otp_root')
+  let b:root = '../test-files/erlang/kerl_otp_root'
+
+  call ale#test#SetFilename(b:root . '/lib/stdlib-4.1.1/array.erl')
+  AssertLSPProject ale#test#GetFilename(b:root)