fix node hooks when NPM_CONFIG_USERCONFIG is set

pre_commit/languages/node.py

@@ -10,6 +10,7 @@
 from pre_commit import parse_shebang
 from pre_commit.envcontext import envcontext
 from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import UNSET
 from pre_commit.envcontext import Var
 from pre_commit.hook import Hook
 from pre_commit.languages import helpers
@@ -56,6 +57,8 @@ def get_env_patch(venv: str) -> PatchesT:
         ('NODE_VIRTUAL_ENV', venv),
         ('NPM_CONFIG_PREFIX', install_prefix),
         ('npm_config_prefix', install_prefix),
+        ('NPM_CONFIG_USERCONFIG', UNSET),
+        ('npm_config_userconfig', UNSET),
         ('NODE_PATH', os.path.join(venv, lib_dir, 'node_modules')),
         ('PATH', (bin_dir(venv), os.pathsep, Var('PATH'))),
     )

tests/repository_test.py

@@ -260,6 +260,14 @@ def test_run_versioned_node_hook(tempdir_factory, store):
     )
 
 
+@xfailif_windows  # pragma: win32 no cover
+def test_node_hook_with_npm_userconfig_set(tempdir_factory, store, tmpdir):
+    cfg = tmpdir.join('cfg')
+    cfg.write('cache=/dne\n')
+    with mock.patch.dict(os.environ, NPM_CONFIG_USERCONFIG=str(cfg)):
+        test_run_a_node_hook(tempdir_factory, store)
+
+
 def test_run_a_ruby_hook(tempdir_factory, store):
     _test_hook_repo(
         tempdir_factory, store, 'ruby_hooks_repo',