Improve the parsing of requirement files

pip_manage/pip_purge.py

@@ -117,7 +117,7 @@ def _is_installed(package: str) -> bool:
     return True
 
 
-def _parse_requirements(
+def _get_distribution_requirements(
     requirements: list[str] | None,
     *,
     ignore_extra: bool,
@@ -146,7 +146,11 @@ def _get_required_by(package: str, *, ignore_extra: bool) -> frozenset[str]:
         dist.name
         for dist in importlib.metadata.distributions()
         if dist.name != package
-        and (package in _parse_requirements(dist.requires, ignore_extra=ignore_extra))
+        and package
+        in _get_distribution_requirements(
+            dist.requires,
+            ignore_extra=ignore_extra,
+        )
     )
 
 
@@ -161,19 +165,30 @@ def _get_dependencies_of_package(
     ignore_extra: bool,
 ) -> _DependencyInfo:
     assert _is_installed(package)
-    dependencies: frozenset[str] = _parse_requirements(
+    dependencies: frozenset[str] = _get_distribution_requirements(
         importlib.metadata.distribution(package).requires,
         ignore_extra=ignore_extra,
     )
     dependents: frozenset[str] = _get_required_by(package, ignore_extra=ignore_extra)
     return _DependencyInfo(dependencies, dependents)
 
 
+def _extract_package_from_requirements_file_line(requirement: str) -> str:
+    assert not requirement.lstrip().startswith("#")
+    for char in "#;":  # do not change order
+        requirement = requirement.partition(char)[0].strip()
+    for char in "!<>=":  # also do not change order
+        if char in requirement:
+            return requirement.partition(char)[0].strip()
+    return requirement.strip()
+
+
 def _read_from_requirements(requirement_files: list[Path]) -> list[str]:
     return [
-        requirement.strip()
+        _extract_package_from_requirements_file_line(line)
         for requirement_file in requirement_files
-        for requirement in requirement_file.read_text(encoding="utf-8").splitlines()
+        for line in requirement_file.read_text(encoding="utf-8").splitlines()
+        if not line.lstrip().startswith("#")
     ]
 
 
@@ -209,7 +224,9 @@ def main(  # pylint: disable=R0914, R0915  # noqa: PLR0915
             ", ".join(formatted_unrecognized_arg),
         )
     try:
-        requirements: list[str] = _read_from_requirements(args.requirements)
+        requirements: list[str] = _read_from_requirements(
+            args.requirements,
+        )
     except OSError as err:
         logger.error("Could not open requirements file: %s", err)
         return 1

tests/pip_purge_test.py

@@ -176,12 +176,12 @@ def test_is_installed_with_mocked_package_found() -> None:
         assert pip_purge._is_installed("test")
 
 
-def test_parse_requirements_without_ignoring_extra() -> None:
+def test_parse_distribution_requirements_without_ignoring_extra() -> None:
     with mock.patch(
         "importlib.metadata.distribution",
         side_effect=_raise_package_not_found_error_when_package_c,
     ):
-        assert pip_purge._parse_requirements(
+        assert pip_purge._get_distribution_requirements(
             [
                 "package_a",
                 "package_b <2.0,>=1.4",
@@ -192,12 +192,12 @@ def test_parse_requirements_without_ignoring_extra() -> None:
         ) == frozenset(("package_a", "package_b", "package_d"))
 
 
-def test_parse_requirements_ignoring_extra() -> None:
+def test_parse_distribution_requirements_ignoring_extra() -> None:
     with mock.patch(
         "importlib.metadata.distribution",
         side_effect=_raise_package_not_found_error_when_package_c,
     ):
-        assert pip_purge._parse_requirements(
+        assert pip_purge._get_distribution_requirements(
             [
                 "package_a",
                 "package_b <2.0,>=1.4",
@@ -398,15 +398,33 @@ def test_freeze_packages(tmp_path: Path) -> None:
     )
 
 
+@pytest.mark.parametrize(
+    ("requirement", "package_name"),
+    [
+        ("package_a", "package_a"),
+        ("package_b <2.0,>=1.4", "package_b"),
+        ("package_c <2.0,>=1.4;python_version<'3.11'", "package_c"),
+        ("package_d!=3.0", "package_d"),
+        ("  package_e#comment", "package_e"),
+    ],
+)
+def test_parse_requirements_file_line(requirement: str, package_name: str) -> None:
+    assert (
+        pip_purge._extract_package_from_requirements_file_line(requirement)
+        == package_name
+    )
+
+
 def test_read_requirements(tmp_path: Path) -> None:
     tmp_file1: Path = tmp_path / "requirements1.txt"
-    tmp_file1.write_text("package_a\npackage_b\n")
+    tmp_file1.write_text("package_a<2.0,>=1.4\npackage_b;python_version<'3.11'\n")
     tmp_file2: Path = tmp_path / "requirements2.txt"
-    tmp_file2.write_text("package_c\n")
+    tmp_file2.write_text("package_c\n#test\npackage_d!=3.0\n")
     assert pip_purge._read_from_requirements([tmp_file1, tmp_file2]) == [
         "package_a",
         "package_b",
         "package_c",
+        "package_d",
     ]