Close #4541 - Fix Haskell project root detection

We weren't joining and returning paths correctly for detecting project
roots for Haskell projects, and now we are.

Co-authored-by: Rodrigo Mesquita <rodrigo.m.mesquita@gmail.com>

7 files changed, 13 insertions, 2 deletions

diff --git a/ale_linters/haskell/hls.vim b/ale_linters/haskell/hls.vim
index 7f9efc38..7f7f42e1 100644
--- a/ale_linters/haskell/hls.vim
+++ b/ale_linters/haskell/hls.vim
@@ -16,8 +16,9 @@ function! ale_linters#haskell#hls#FindRootFile(buffer) abort
 
     for l:path in ale#path#Upwards(expand('#' . a:buffer . ':p:h'))
         for l:root_file in l:serach_root_files
-            if filereadable(l:path . l:root_file)
-                return l:path
+            if filereadable(l:path . '/' . l:root_file)
+                " Add on / so fnamemodify(..., ':h') below keeps the path.
+                return l:path . '/'
             endif
         endfor
     endfor
diff --git a/test/linter/test_haskell_hls.vader b/test/linter/test_haskell_hls.vader
index 4452d53c..59a50078 100644
--- a/test/linter/test_haskell_hls.vader
+++ b/test/linter/test_haskell_hls.vader
@@ -30,3 +30,13 @@ Execute(Should accept configuration settings):
   AssertLSPConfig {}
   let b:ale_haskell_hls_config = {'haskell': {'maxCompletions': 250}}
   AssertLSPConfig {'haskell': {'maxCompletions': 250}}
+
+Execute(We should detect the root with cabal.project files, preferred over *.cabal files):
+  call ale#test#SetFilename('../test-files/haskell/haskell-packages-project/package-a/src/folder/dummy.hs')
+
+  AssertLSPProject ale#test#GetFilename('../test-files/haskell/haskell-packages-project')
+
+Execute(We should a project root with *.cabal files):
+  call ale#test#SetFilename('../test-files/haskell/haskell-simple-package/package-a/src/folder/dummy.hs')
+
+  AssertLSPProject ale#test#GetFilename('../test-files/haskell/haskell-simple-package/package-a')
diff --git a/test/test-files/haskell/haskell-packages-project/cabal.project b/test/test-files/haskell/haskell-packages-project/cabal.project
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/test-files/haskell/haskell-packages-project/cabal.project
diff --git a/test/test-files/haskell/haskell-packages-project/package-a/package-a.cabal b/test/test-files/haskell/haskell-packages-project/package-a/package-a.cabal
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/test-files/haskell/haskell-packages-project/package-a/package-a.cabal
diff --git a/test/test-files/haskell/haskell-packages-project/package-a/src/folder/dummy.hs b/test/test-files/haskell/haskell-packages-project/package-a/src/folder/dummy.hs
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/test-files/haskell/haskell-packages-project/package-a/src/folder/dummy.hs
diff --git a/test/test-files/haskell/haskell-simple-package/package-a/package-a.cabal b/test/test-files/haskell/haskell-simple-package/package-a/package-a.cabal
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/test-files/haskell/haskell-simple-package/package-a/package-a.cabal
diff --git a/test/test-files/haskell/haskell-simple-package/package-a/src/folder/dummy.hs b/test/test-files/haskell/haskell-simple-package/package-a/src/folder/dummy.hs
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/test-files/haskell/haskell-simple-package/package-a/src/folder/dummy.hs