Remove redundant code paths

We are now constrained on `pip >= 21.2.4` (bcfd93c). This commit
elliminates code paths that were there previously in order to cater to
the older versions of Pip:

- `PipSession` is now only found in `pip._internal._network.session`.
- `install_req_from_line` is always used.
- `search_packages_info` now always gives us a generator that yields
  `pip._internal.commands.show._PackageInfo` objects (not `dict`).

Author: MrMino

pip_check_reqs/common.py

@@ -13,11 +13,8 @@
 
 from . import __version__
 
-# Between different versions of pip the location of PipSession has changed.
-try:
-    from pip._internal.network.session import PipSession
-except ImportError:  # pragma: no cover
-    from pip._internal.download import PipSession
+from pip._internal.network.session import PipSession
+from pip._internal.req.constructors import install_req_from_line
 from pip._internal.req.req_file import parse_requirements
 
 
@@ -137,16 +134,9 @@ def find_required_modules(options, requirements_filename: str):
     explicit = set()
     for requirement in parse_requirements(requirements_filename,
                                           session=PipSession()):
-        try:
-            requirement_name = requirement.name
-        # The type of "requirement" changed between pip versions.
-        # We exclude the "except" from coverage so that on any pip version we
-        # can report 100% coverage.
-        except AttributeError:  # pragma: no cover
-            from pip._internal.req.constructors import install_req_from_line
-            requirement_name = install_req_from_line(
-                requirement.requirement,
-            ).name
+        requirement_name = install_req_from_line(
+            requirement.requirement,
+        ).name
 
         if options.ignore_reqs(requirement):
             log.debug('ignoring requirement: %s', requirement_name)
@@ -193,13 +183,10 @@ def ignorer(ignore_cfg):
     def f(candidate, ignore_cfg=ignore_cfg):
         for ignore in ignore_cfg:
             try:
-                from pip._internal.req.constructors import (
-                    install_req_from_line,
-                )
-                candidate_path = install_req_from_line(  # pragma: no cover
+                candidate_path = install_req_from_line(
                     candidate.requirement,
                 ).name
-            except (ImportError, AttributeError):
+            except AttributeError:
                 try:
                     candidate_path = candidate.name
                 except AttributeError:

pip_check_reqs/find_extra_reqs.py

@@ -27,26 +27,21 @@ def find_extra_reqs(options, requirements_filename):
     )
 
     for package in search_packages_info(all_pkgs):
-        if isinstance(package, dict):  # pragma: no cover
-            package_name = package['name']
-            package_location = package['location']
-            package_files = package.get('files', []) or []
-        else:  # pragma: no cover
-            package_name = package.name
-            package_location = package.location
-            package_files = []
-            for item in (package.files or []):
-                here = pathlib.Path('.').resolve()
-                item_location_rel = (pathlib.Path(package_location) / item)
-                item_location = item_location_rel.resolve()
-                try:
-                    relative_item_location = item_location.relative_to(here)
-                except ValueError:
-                    # Ideally we would use Pathlib.is_relative_to rather than
-                    # checking for a ValueError, but that is only available in
-                    # Python 3.9+.
-                    relative_item_location = item_location
-                package_files.append(str(relative_item_location))
+        package_name = package.name
+        package_location = package.location
+        package_files = []
+        for item in (package.files or []):
+            here = pathlib.Path('.').resolve()
+            item_location_rel = (pathlib.Path(package_location) / item)
+            item_location = item_location_rel.resolve()
+            try:
+                relative_item_location = item_location.relative_to(here)
+            except ValueError:
+                # Ideally we would use Pathlib.is_relative_to rather than
+                # checking for a ValueError, but that is only available in
+                # Python 3.9+.
+                relative_item_location = item_location
+            package_files.append(str(relative_item_location))
 
         log.debug('installed package: %s (at %s)', package_name,
                   package_location)

pip_check_reqs/find_missing_reqs.py

@@ -8,11 +8,8 @@
 
 from packaging.utils import canonicalize_name
 from pip._internal.commands.show import search_packages_info
-# Between different versions of pip the location of PipSession has changed.
-try:
-    from pip._internal.network.session import PipSession
-except ImportError:  # pragma: no cover
-    from pip._internal.download import PipSession
+from pip._internal.network.session import PipSession
+from pip._internal.req.constructors import install_req_from_line
 from pip._internal.req.req_file import parse_requirements
 
 from pip_check_reqs import common
@@ -34,26 +31,21 @@ def find_missing_reqs(options, requirements_filename):
     )
 
     for package in search_packages_info(all_pkgs):
-        if isinstance(package, dict):  # pragma: no cover
-            package_name = package['name']
-            package_location = package['location']
-            package_files = package.get('files', []) or []
-        else:  # pragma: no cover
-            package_name = package.name
-            package_location = package.location
-            package_files = []
-            for item in (package.files or []):
-                here = pathlib.Path('.').resolve()
-                item_location_rel = (pathlib.Path(package_location) / item)
-                item_location = item_location_rel.resolve()
-                try:
-                    relative_item_location = item_location.relative_to(here)
-                except ValueError:
-                    # Ideally we would use Pathlib.is_relative_to rather than
-                    # checking for a ValueError, but that is only available in
-                    # Python 3.9+.
-                    relative_item_location = item_location
-                package_files.append(str(relative_item_location))
+        package_name = package.name
+        package_location = package.location
+        package_files = []
+        for item in (package.files or []):
+            here = pathlib.Path('.').resolve()
+            item_location_rel = (pathlib.Path(package_location) / item)
+            item_location = item_location_rel.resolve()
+            try:
+                relative_item_location = item_location.relative_to(here)
+            except ValueError:
+                # Ideally we would use Pathlib.is_relative_to rather than
+                # checking for a ValueError, but that is only available in
+                # Python 3.9+.
+                relative_item_location = item_location
+            package_files.append(str(relative_item_location))
 
         log.debug('installed package: %s (at %s)', package_name,
                   package_location)
@@ -89,16 +81,9 @@ def find_missing_reqs(options, requirements_filename):
         requirements_filename,
         session=PipSession(),
     ):
-        try:
-            requirement_name = requirement.name
-        # The type of "requirement" changed between pip versions.
-        # We exclude the "except" from coverage so that on any pip version we
-        # can report 100% coverage.
-        except AttributeError:  # pragma: no cover
-            from pip._internal.req.constructors import install_req_from_line
-            requirement_name = install_req_from_line(
-                requirement.requirement,
-            ).name
+        requirement_name = install_req_from_line(
+            requirement.requirement,
+        ).name
 
         log.debug('found requirement: %s', requirement_name)
         explicit.add(canonicalize_name(requirement_name))

tests/__init__.py

@@ -0,0 +1,9 @@
+from typing import List, Optional, NamedTuple
+
+
+# A stand-in for pip._internal.commands.show._PackageInfo, as returned by
+# search_packages_info from the same module
+class _PackageInfo(NamedTuple):
+    name: str
+    location: str
+    files: Optional[List[str]]

tests/package_info_mock.py

@@ -12,6 +12,8 @@
 
 from pip_check_reqs import find_extra_reqs, common
 
+from .package_info_mock import _PackageInfo
+
 
 @pytest.fixture
 def fake_opts():
@@ -68,11 +70,10 @@ class FakePathDistribution:
         pretend.call_recorder(lambda **kwargs: installed_distributions),
     )
     packages_info = [
-        dict(name='spam',
-             location='site-spam',
-             files=['spam/__init__.py', 'spam/shrub.py']),
-        dict(name='shrub', location='site-spam', files=['shrub.py']),
-        dict(name='pass', location='site-spam', files=['pass.py']),
+        _PackageInfo(name='spam', location='site-spam',
+                     files=['spam/__init__.py', 'spam/shrub.py']),
+        _PackageInfo(name='shrub', location='site-spam', files=['shrub.py']),
+        _PackageInfo(name='pass', location='site-spam', files=['pass.py']),
     ]
 
     monkeypatch.setattr(find_extra_reqs, 'search_packages_info',

tests/test_find_extra_reqs.py

@@ -12,6 +12,8 @@
 
 from pip_check_reqs import find_missing_reqs, common
 
+from .package_info_mock import _PackageInfo
+
 
 @pytest.fixture
 def fake_opts():
@@ -67,11 +69,11 @@ class FakePathDistribution:
         pretend.call_recorder(lambda **kwargs: installed_distributions),
     )
     packages_info = [
-        dict(name='spam',
-             location='site-spam',
-             files=['spam/__init__.py', 'spam/shrub.py']),
-        dict(name='shrub', location='site-spam', files=['shrub.py']),
-        dict(name='pass', location='site-spam', files=['pass.py']),
+        _PackageInfo(name='spam',
+                     location='site-spam',
+                     files=['spam/__init__.py', 'spam/shrub.py']),
+        _PackageInfo(name='shrub', location='site-spam', files=['shrub.py']),
+        _PackageInfo(name='pass', location='site-spam', files=['pass.py']),
     ]
 
     monkeypatch.setattr(find_missing_reqs, 'search_packages_info',