feat(dependency): add PEP 508 parser using packaging

python/deptry/dependency.py

@@ -4,7 +4,9 @@
 import re
 from contextlib import suppress
 from importlib import metadata
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Mapping
+
+from packaging.requirements import InvalidRequirement, Requirement
 
 if TYPE_CHECKING:
     from collections.abc import Sequence
@@ -132,3 +134,18 @@ def _get_top_level_module_names_from_record_file(distribution: Distribution) ->
         matches = re.finditer(r"^(?!__)([a-zA-Z0-9-_]+)(?:/|\.py,)", metadata_records, re.MULTILINE)
 
         return {x.group(1) for x in matches}
+
+
+def parse_pep_508_dependency(
+    specification: str, definition_file: Path, package_module_name_map: Mapping[str, Sequence[str]]
+) -> Dependency | None:
+    try:
+        requirement = Requirement(specification)
+    except InvalidRequirement:
+        return None
+
+    return Dependency(
+        name=requirement.name,
+        definition_file=definition_file,
+        module_names=package_module_name_map.get(requirement.name),
+    )

tests/unit/test_dependency.py

@@ -2,9 +2,12 @@
 
 from importlib.metadata import PackageNotFoundError
 from pathlib import Path
+from typing import Any
 from unittest.mock import patch
 
-from deptry.dependency import Dependency
+import pytest
+
+from deptry.dependency import Dependency, parse_pep_508_dependency
 
 
 def test_simple_dependency() -> None:
@@ -99,3 +102,46 @@ def test_not_predefined_and_not_installed() -> None:
 
     assert dependency.name == "Foo-bar"
     assert dependency.top_levels == {"foo_bar"}
+
+
+@pytest.mark.parametrize(
+    ("specification", "definition_file", "package_module_name_map", "expected"),
+    [
+        (
+            "foo",
+            Path("pyproject.toml"),
+            {},
+            {
+                "name": "foo",
+                "definition_file": Path("pyproject.toml"),
+                "found": False,
+                "top_levels": {"foo"},
+            },
+        ),
+        (
+            'foobar[extra]==1.2.3; python_version < "3.9"',
+            Path("requirements.txt"),
+            {"foobar": ["foo"], "barfoo": ["bar"]},
+            {
+                "name": "foobar",
+                "definition_file": Path("requirements.txt"),
+                "found": False,
+                "top_levels": {"foo"},
+            },
+        ),
+    ],
+)
+def test_parse_pep_508_dependency(
+    specification: str,
+    definition_file: Path,
+    package_module_name_map: dict[str, list[str]],
+    expected: dict[str, Any],
+) -> None:
+    dependency = parse_pep_508_dependency(specification, definition_file, package_module_name_map)
+
+    for dependency_key, expected_value in expected.items():
+        assert getattr(dependency, dependency_key) == expected_value
+
+
+def test_parse_pep_508_dependency_invalid_definition() -> None:
+    assert parse_pep_508_dependency("an_incorrect_definition=1.2.3", Path("pyproject.toml"), {}) is None