add handling for more path-based version specifiers

These are all valid version specifiers for path-style packages in
package.json/yarn.lock:

./some/relative/path
../some/relative/path
file:some/relative/path
file:../some/relative/path
link:some/relative/path
link:../some/relative/path\
/some/absolute/path

Ensure that the Package class provides a path in each of these cases.

Signed-off-by: Taylor Madore <tmadore@redhat.com>

pyarn/lockfile.py

@@ -18,7 +18,8 @@
 import json
 import logging
 import re
-from typing import Pattern
+from pathlib import Path
+from typing import Optional, Pattern
 
 from ply import lex, yacc
 
@@ -91,8 +92,8 @@ def from_dict(cls, raw_name, data):
             alias = name
             name, _version = _must_match(name_at_version, _remove_prefix(_version, "npm:")).groups()
 
-        if _version and _version.startswith("file:"):
-            path = _remove_prefix(_version, "file:")
+        if _version:
+            path = cls.get_path_from_version_specifier(_version)
 
         return cls(
             name=name,
@@ -104,6 +105,22 @@ def from_dict(cls, raw_name, data):
             alias=alias,
         )
 
+    @staticmethod
+    def get_path_from_version_specifier(version: str) -> Optional[str]:
+        """Return the path from a package.json file dependency version specifier."""
+        version_path = Path(version)
+
+        if version.startswith("file:"):
+            return _remove_prefix(version, "file:")
+        elif version.startswith("link:"):
+            return _remove_prefix(version, "link:")
+        elif version_path.is_absolute() or version.startswith(("./", "../")):
+            return str(version_path)
+        else:
+            # Some non-path version specifier, (e.g. "1.0.0" or a web link)
+            # See https://docs.npmjs.com/cli/v10/configuring-npm/package-json#dependencies
+            return None
+
 
 def _remove_prefix(s: str, prefix: str) -> str:
     return s[len(prefix) :]

tests/test_lockfile.py

@@ -161,17 +161,46 @@ def test_packages_checksum():
     assert packages[0].path is None
 
 
-def test_path():
-    data = '"breakfast@file:some/relative/path":\n  version "0.0.0"'
+@pytest.mark.parametrize(
+    "data, expected_path",
+    [
+        pytest.param(
+            '"breakfast@file:some/relative/path":\n  version "0.0.0"',
+            "some/relative/path",
+            id="relpath_with_file_prefix",
+        ),
+        pytest.param(
+            '"breakfast@link:some/relative/path":\n  version "0.0.0"',
+            "some/relative/path",
+            id="relpath_with_link_prefix",
+        ),
+        pytest.param(
+            '"breakfast@./some/relative/path":\n  version "0.0.0"',
+            "some/relative/path",
+            id="relpath_with_dot_prefix",
+        ),
+        pytest.param(
+            '"breakfast@../some/relative/path":\n  version "0.0.0"',
+            "../some/relative/path",
+            id="relpath_to_parent_dir",
+        ),
+        pytest.param(
+            '"breakfast@/some/absolute/path":\n  version "0.0.0"',
+            "/some/absolute/path",
+            id="absolute_path",
+        ),
+    ],
+)
+def test_package_with_path(data: str, expected_path: str) -> None:
     lock = lockfile.Lockfile.from_str(data)
     packages = lock.packages()
     assert len(packages) == 1
     assert packages[0].name == "breakfast"
     assert packages[0].version == "0.0.0"
     assert packages[0].checksum is None
     assert packages[0].url is None
-    assert packages[0].path == "some/relative/path"
-    assert packages[0].relpath == "some/relative/path"  # test backwards compatibility
+    assert packages[0].path == expected_path
+    assert packages[0].relpath == expected_path  # test backwards compatibility
 
 
 def test_package_with_comma():