Add naive and untested version of Lua language support.

tests/languages/lua_test.py

@@ -0,0 +1,55 @@
+import os
+from unittest import mock
+
+import pytest
+
+import pre_commit.constants as C
+from pre_commit.languages import lua
+from testing.util import xfailif_windows
+
+
+@pytest.mark.parametrize(
+    'lua_name', ('lua', 'lua5.4', 'lua-5.4', 'lua5.4.exe'),
+)
+def test_find_lua(tmp_path, lua_name):
+    """The language support can find common lua executable names."""
+    lua_file = tmp_path / lua_name
+    lua_file.touch(0o555)
+    with mock.patch.dict(os.environ, {'PATH': str(tmp_path)}):
+        lua_executable = lua._find_lua(C.DEFAULT)
+    assert lua_name in lua_executable
+
+
+def test_find_lua_language_version(tmp_path):
+    """Language discovery can find a specific version."""
+    lua_file = tmp_path / 'lua5.99'
+    lua_file.touch(0o555)
+    with mock.patch.dict(os.environ, {'PATH': str(tmp_path)}):
+        lua_executable = lua._find_lua('5.99')
+    assert 'lua5.99' in lua_executable
+
+
+@pytest.mark.parametrize(
+    ('invalid', 'mode'),
+    (
+        ('foobar', 0o555),
+        ('luac', 0o555),
+        # Windows doesn't respect the executable checking.
+        pytest.param('lua5.4', 0o444, marks=xfailif_windows),
+    ),
+)
+def test_find_lua_fail(tmp_path, invalid, mode):
+    """No lua executable on the system will fail."""
+    non_lua_file = tmp_path / invalid
+    non_lua_file.touch(mode)
+    with mock.patch.dict(os.environ, {'PATH': str(tmp_path)}):
+        with pytest.raises(ValueError):
+            lua._find_lua(C.DEFAULT)
+
+
+@mock.patch.object(lua, 'cmd_output')
+def test_bad_package_path(mock_cmd_output):
+    """A package path missing path info returns an unknown version."""
+    mock_cmd_output.return_value = (0, '', '')
+    with pytest.raises(ValueError):
+        lua._get_lua_path_version('lua')