fix: Use JSON to parse npm pack output.

ovcharenko · ovcharenko · commit bbabec288a3e · 2025-09-26T18:05:27.000+03:00
diff --git a/pre_commit/languages/node.py b/pre_commit/languages/node.py
@@ -2,6 +2,7 @@
 
 import contextlib
 import functools
+import json
 import os
 import sys
 from collections.abc import Generator
@@ -98,8 +99,28 @@ def install_environment(
         )
         lang_base.setup_cmd(prefix, local_install_cmd)
 
-        _, pkg, _ = cmd_output('npm', 'pack', cwd=prefix.prefix_dir)
-        pkg = prefix.path(pkg.strip())
+        _, pkg, _ = cmd_output(
+            'npm', 'pack', '--json', '--ignore-scripts', cwd=prefix.prefix_dir,
+        )
+        try:
+            pkg_json = json.loads(pkg)
+        except json.JSONDecodeError as e:
+            raise ValueError('Failed to parse npm pack output as JSON.') from e
+
+        if not pkg_json:
+            raise ValueError('JSON array from npm pack is empty.')
+
+        if not isinstance(pkg_json, list):
+            raise ValueError('Expected npm pack output to be a JSON array.')
+
+        filename = pkg_json[0].get('filename')
+        if filename is None:
+            raise KeyError(
+                "Key 'filename' not found in the first element "
+                'of the JSON array.',
+            )
+
+        pkg = prefix.path(filename)
 
         install = ('npm', 'install', '-g', pkg, *additional_dependencies)
         lang_base.setup_cmd(prefix, install)
diff --git a/tests/languages/node_test.py b/tests/languages/node_test.py
@@ -113,8 +113,8 @@ def test_installs_without_links_outside_env(tmpdir):
         assert cmd_output('foo')[1] == 'success!\n'
 
 
-def _make_hello_world(tmp_path):
-    package_json = '''\
+def _make_hello_world(tmp_path, package_json=None):
+    package_json = package_json or '''\
 {"name": "t", "version": "0.0.1", "bin": {"node-hello": "./bin/main.js"}}
 '''
     tmp_path.joinpath('package.json').write_text(package_json)
@@ -132,6 +132,20 @@ def test_node_hook_system(tmp_path):
     assert ret == (0, b'Hello World\n')
 
 
+def test_node_with_prepare_script(tmp_path):
+    package_json = '''
+{
+  "name": "t",
+  "version": "0.0.1",
+  "bin": {"node-hello": "./bin/main.js"},
+  "scripts": {"prepare": "echo prepare"}
+}
+'''
+    _make_hello_world(tmp_path, package_json)
+    ret = run_language(tmp_path, node, 'node-hello')
+    assert ret == (0, b'Hello World\n')
+
+
 def test_node_with_user_config_set(tmp_path):
     cfg = tmp_path.joinpath('cfg')
     cfg.write_text('cache=/dne\n')
