5 files changed, 129 insertions, 0 deletions
diff --git a/ale_linters/typescript/deno.vim b/ale_linters/typescript/deno.vim
new file mode 100644
index 00000000..051cb208
--- /dev/null
+++ b/ale_linters/typescript/deno.vim
@@ -0,0 +1,25 @@
+" Author: Mohammed Chelouti - https://github.com/motato1
+" Description: Deno lsp linter for TypeScript files.
+
+call ale#linter#Define('typescript', {
+\   'name': 'deno',
+\   'lsp': 'stdio',
+\   'executable': function('ale#handlers#deno#GetExecutable'),
+\   'command': '%e lsp',
+\   'project_root': function('ale#handlers#deno#GetProjectRoot'),
+\   'initialization_options': function('ale_linters#typescript#deno#GetInitializationOptions'),
+\})
+
+function! ale_linters#typescript#deno#GetInitializationOptions(buffer) abort
+    let l:options = {
+    \   'enable': v:true,
+    \   'lint': v:true,
+    \   'unstable': v:false,
+    \   }
+
+    if ale#Var(a:buffer, 'deno_unstable')
+        let l:options.unstable = v:true
+    endif
+
+    return l:options
+endfunction
diff --git a/autoload/ale/handlers/deno.vim b/autoload/ale/handlers/deno.vim
index 636c25da..4bf4546a 100644
--- a/autoload/ale/handlers/deno.vim
+++ b/autoload/ale/handlers/deno.vim
@@ -3,7 +3,50 @@
 
 call ale#Set('deno_executable', 'deno')
 call ale#Set('deno_unstable', 0)
+call ale#Set('deno_lsp_project_root', '')
 
 function! ale#handlers#deno#GetExecutable(buffer) abort
     return ale#Var(a:buffer, 'deno_executable')
 endfunction
+
+" Find project root for Deno's language server.
+"
+" Deno projects do not require a project or configuration file at the project root.
+" This means the root directory has to be guessed,
+" unless it is explicitly specified by the user.
+"
+" The project root is determined by ...
+" 1. using a user-specified value from deno_lsp_project_root
+" 2. looking for common top-level files/dirs
+" 3. using the buffer's directory
+function! ale#handlers#deno#GetProjectRoot(buffer) abort
+    let l:project_root = ale#Var(a:buffer, 'deno_lsp_project_root')
+
+    if !empty(l:project_root)
+        return l:project_root
+    endif
+
+    let l:possible_project_roots = [
+    \   'tsconfig.json',
+    \   '.git',
+    \   bufname(a:buffer),
+    \]
+
+    for l:possible_root in l:possible_project_roots
+        let l:project_root = ale#path#FindNearestFile(a:buffer, l:possible_root)
+
+        if empty(l:project_root)
+            let l:project_root = ale#path#FindNearestDirectory(a:buffer, l:possible_root)
+        endif
+
+        if !empty(l:project_root)
+            " dir:p expands to /full/path/to/dir/ whereas
+            " file:p expands to /full/path/to/file (no trailing slash)
+            " Appending '/' ensures that :h:h removes the path's last segment
+            " regardless of whether it is a directory or not.
+            return fnamemodify(l:project_root . '/', ':p:h:h')
+        endif
+    endfor
+
+    return ''
+endfunction
diff --git a/test/command_callback/test_typescript_deno_lsp.vader b/test/command_callback/test_typescript_deno_lsp.vader
new file mode 100644
index 00000000..b6e4db0e
--- /dev/null
+++ b/test/command_callback/test_typescript_deno_lsp.vader
@@ -0,0 +1,61 @@
+Before:
+  let g:ale_deno_unstable = 0
+  let g:ale_deno_executable = 'deno'
+  let g:ale_deno_project_root = ''
+
+  runtime autoload/ale/handlers/deno.vim
+  call ale#assert#SetUpLinterTest('typescript', 'deno')
+
+After:
+  call ale#assert#TearDownLinterTest()
+
+Execute(Should set deno lsp for TypeScript projects using stable Deno API):
+  AssertLSPLanguage 'typescript'
+  AssertLSPConfig {}
+  AssertLSPProject ale#path#Simplify(g:dir . '/../..')
+  AssertLSPOptions {
+  \   'enable': v:true,
+  \   'lint': v:true,
+  \   'unstable': v:false
+  \}
+
+Execute(Should set deno lsp using unstable Deno API if enabled by user):
+  let g:ale_deno_unstable = 1
+  AssertLSPLanguage 'typescript'
+  AssertLSPConfig {}
+  AssertLSPProject ale#path#Simplify(g:dir . '/../..')
+  AssertLSPOptions {
+  \   'enable': v:true,
+  \   'lint': v:true,
+  \   'unstable': v:true
+  \}
+
+Execute(Should find project root containing tsconfig.json):
+  call ale#test#SetFilename('../typescript/test.ts')
+  AssertLSPLanguage 'typescript'
+  AssertLSPConfig {}
+  AssertLSPProject ale#path#Simplify(g:dir . '/../typescript')
+  AssertLSPOptions {
+  \   'enable': v:true,
+  \   'lint': v:true,
+  \   'unstable': v:false
+  \}
+
+Execute(Should use user-specified project root):
+  let g:ale_deno_lsp_project_root = '/'
+
+  call ale#test#SetFilename('../typescript/test.ts')
+  AssertLSPLanguage 'typescript'
+  AssertLSPConfig {}
+  AssertLSPProject '/'
+  AssertLSPOptions {
+  \   'enable': v:true,
+  \   'lint': v:true,
+  \   'unstable': v:false
+  \}
+
+
+Execute(Check Deno LSP command):
+  AssertLinter 'deno', [
+  \ ale#Escape('deno') . ' lsp',
+  \]
diff --git a/test/typescript/test.ts b/test/typescript/test.ts
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/typescript/test.ts
diff --git a/test/typescript/tsconfig.json b/test/typescript/tsconfig.json
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/typescript/tsconfig.json