Fix IndexError when shebang is just '#!/usr/bin/env'

identify/identify.py

@@ -191,14 +191,14 @@ def parse_shebang(bytesio: IO[bytes]) -> tuple[str, ...]:
             return ()
 
     cmd = tuple(_shebang_split(first_line.strip()))
-    if cmd and cmd[0] == '/usr/bin/env':
-        if cmd[1] == '-S':
-            cmd = cmd[2:]
-        else:
-            cmd = cmd[1:]
+    if cmd[:2] == ('/usr/bin/env', '-S'):
+        cmd = cmd[2:]
+    elif cmd[:1] == ('/usr/bin/env',):
+        cmd = cmd[1:]
+
+    if cmd == ('nix-shell',):
+        return _parse_nix_shebang(bytesio, cmd)
 
-        if cmd == ('nix-shell',):
-            return _parse_nix_shebang(bytesio, cmd)
     return cmd
 
 

tests/identify_test.py

@@ -325,6 +325,8 @@ def test_file_is_text_does_not_exist(tmpdir):
         (b'#!\x00\x00\x00\x00', ()),
         # shebang lines with multiple arguments
         (b'#!/usr/bin/env -S python -u', ('python', '-u')),
+        (b'#!/usr/bin/env', ()),
+        (b'#!/usr/bin/env -S', ()),
     ),
 )
 def test_parse_shebang(s, expected):