8 files changed, 68 insertions, 2 deletions
diff --git a/autoload/ale/handlers/biome.vim b/autoload/ale/handlers/biome.vim
index a12bfe83..47384e56 100644
--- a/autoload/ale/handlers/biome.vim
+++ b/autoload/ale/handlers/biome.vim
@@ -5,6 +5,7 @@ call ale#Set('biome_executable', 'biome')
 call ale#Set('biome_use_global', get(g:, 'ale_use_global_executables', 0))
 call ale#Set('biome_options', '')
 call ale#Set('biome_fixer_apply_unsafe', 0)
+call ale#Set('biome_lsp_project_root', '')
 
 function! ale#handlers#biome#GetExecutable(buffer) abort
     return ale#path#FindExecutable(a:buffer, 'biome', [
@@ -30,7 +31,35 @@ function! ale#handlers#biome#GetLanguage(buffer) abort
 endfunction
 
 function! ale#handlers#biome#GetProjectRoot(buffer) abort
-    let l:biome_file = ale#path#FindNearestFile(a:buffer, 'biome.json')
+    let l:project_root = ale#Var(a:buffer, 'biome_lsp_project_root')
 
-    return !empty(l:biome_file) ? fnamemodify(l:biome_file, ':h') : ''
+    if !empty(l:project_root)
+        return l:project_root
+    endif
+
+    let l:possible_project_roots = [
+    \   'biome.json',
+    \   'biome.jsonc',
+    \   'package.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/doc/ale-typescript.txt b/doc/ale-typescript.txt
index 967287a2..f22b6586 100644
--- a/doc/ale-typescript.txt
+++ b/doc/ale-typescript.txt
@@ -35,6 +35,22 @@ g:ale_biome_fixer_apply_unsafe                 *g:ale_biome_fixer_apply_unsafe*
   If set to `1`, biome will apply unsafe fixes along with safe fixes.
 
 
+g:ale_biome_lsp_project_root                     *g:ale_biome_lsp_project_root*
+                                                 *b:ale_biome_lsp_project_root*
+  Type: |String|
+  Default: `''`
+
+  If this variable is left unset, ALE will try to find the project root by
+  executing the following steps in the given order:
+
+  1. Find an ancestor directory containing a biome.json.
+  2. Find an ancestor directory containing a biome.jsonc.
+  3. Find an ancestor directory containing a package.json.
+  4. Find an ancestor directory containing a .git folder.
+  5. Use the directory of the current buffer (if the buffer was opened from
+     a file).
+
+
 ===============================================================================
 cspell                                                  *ale-typescript-cspell*
 
diff --git a/test/linter/test_biome.vader b/test/linter/test_biome.vader
index c2cd9407..2e5e7aac 100644
--- a/test/linter/test_biome.vader
+++ b/test/linter/test_biome.vader
@@ -1,7 +1,9 @@
 Before:
   Save g:ale_biome_options
+  Save g:ale_biome_lsp_project_root
 
   let g:ale_biome_options = ''
+  let g:ale_biome_lsp_project_root = ''
 
   call ale#assert#SetUpLinterTest('typescript', 'biome')
   call ale#test#SetFilename('test.ts')
@@ -33,3 +35,20 @@ Execute(Uses the filetype as the language):
   call ale#test#SetFilename('test.jsx')
   set filetype=javascriptreact
   AssertLSPLanguage 'javascriptreact'
+
+Execute(Should find project root containing biome.json):
+  call ale#test#SetFilename('../test-files/biome/json/src/test.ts')
+
+  AssertLSPProject ale#path#Simplify(g:dir . '/../test-files/biome/json')
+
+Execute(Should find project root containing biome.jsonc):
+  call ale#test#SetFilename('../test-files/biome/jsonc/src/test.ts')
+
+  AssertLSPProject ale#path#Simplify(g:dir . '/../test-files/biome/jsonc')
+
+Execute(Should use user-specified project root):
+  let g:ale_biome_lsp_project_root = '/'
+
+  call ale#test#SetFilename('../test-files/biome/jsonc/src/test.ts')
+
+  AssertLSPProject '/'
diff --git a/test/linter/test_typescript_deno_lsp.vader b/test/linter/test_typescript_deno_lsp.vader
index 8bae1ae2..c77b2a10 100644
--- a/test/linter/test_typescript_deno_lsp.vader
+++ b/test/linter/test_typescript_deno_lsp.vader
@@ -1,10 +1,12 @@
 Before:
   Save g:ale_deno_import_map
+  Save g:ale_deno_importMap
   Save g:ale_deno_unstable
   Save g:ale_deno_executable
   Save g:ale_deno_lsp_project_root
 
   let g:ale_deno_import_map = 'import_map.json'
+  let g:ale_deno_importMap = ''
   let g:ale_deno_unstable = 0
   let g:ale_deno_executable = 'deno'
   let g:ale_deno_lsp_project_root = ''
diff --git a/test/test-files/biome/json/biome.json b/test/test-files/biome/json/biome.json
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/test-files/biome/json/biome.json
diff --git a/test/test-files/biome/json/src/test.ts b/test/test-files/biome/json/src/test.ts
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/test-files/biome/json/src/test.ts
diff --git a/test/test-files/biome/jsonc/biome.jsonc b/test/test-files/biome/jsonc/biome.jsonc
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/test-files/biome/jsonc/biome.jsonc
diff --git a/test/test-files/biome/jsonc/src/test.ts b/test/test-files/biome/jsonc/src/test.ts
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/test-files/biome/jsonc/src/test.ts