Fix cyclic dependency between 'utils' and '_compat'

The compat subpackage having an `__init__.py` created a cycle with the
introduction of pathlib compatibility tooling. The reason being that we
have...

    utils -> _compat.path_compat
    _compat.pip_compat -> utils

(fine on its own) plus

    _compat -> _compat.pip_compat

which makes `utils -> _compat.path_compat` into a cycle.

This probably indicates some level of code smell -- the situation arises
because pip_compat and utils aren't very clearly defined as distinct --
but for now it's trivial to fix by just getting rid of the subpackage
`__init__.py` imports and making each of these pieces a standalone
module.

Author: sirosen

piptools/_compat/__init__.py

@@ -1,15 +0,0 @@
-from __future__ import annotations
-
-from .pip_compat import (
-    Distribution,
-    create_wheel_cache,
-    get_dev_pkgs,
-    parse_requirements,
-)
-
-__all__ = [
-    "Distribution",
-    "parse_requirements",
-    "create_wheel_cache",
-    "get_dev_pkgs",
-]

piptools/repositories/pypi.py

@@ -30,7 +30,7 @@
 from pip._vendor.packaging.version import _BaseVersion
 from pip._vendor.requests import RequestException, Session
 
-from .._compat import create_wheel_cache
+from .._compat.pip_compat import create_wheel_cache
 from ..exceptions import NoCandidateFound
 from ..logging import log
 from ..utils import (

piptools/resolver.py

@@ -26,7 +26,7 @@
 from piptools.cache import DependencyCache
 from piptools.repositories.base import BaseRepository
 
-from ._compat import create_wheel_cache
+from ._compat.pip_compat import create_wheel_cache
 from .exceptions import PipToolsError
 from .logging import log
 from .utils import (

piptools/scripts/compile.py

@@ -14,7 +14,7 @@
 from pip._internal.req import InstallRequirement
 from pip._internal.utils.misc import redact_auth_from_url
 
-from .._compat import parse_requirements
+from .._compat.pip_compat import parse_requirements
 from ..build import ProjectMetadata, build_project_metadata
 from ..cache import DependencyCache
 from ..exceptions import NoCandidateFound, PipToolsError

piptools/scripts/sync.py

@@ -15,7 +15,7 @@
 from pip._internal.metadata import get_environment
 
 from .. import sync
-from .._compat import Distribution, parse_requirements
+from .._compat.pip_compat import Distribution, parse_requirements
 from ..exceptions import PipToolsError
 from ..logging import log
 from ..repositories import PyPIRepository

piptools/sync.py

@@ -17,7 +17,7 @@
 )
 from pip._vendor.packaging.utils import canonicalize_name
 
-from ._compat import Distribution, get_dev_pkgs
+from ._compat.pip_compat import Distribution, get_dev_pkgs
 from .exceptions import IncompatibleRequirements
 from .logging import log
 from .utils import (

tests/conftest.py

@@ -29,7 +29,7 @@
 from pip._vendor.packaging.version import Version
 from pip._vendor.pkg_resources import Requirement
 
-from piptools._compat import Distribution
+from piptools._compat.pip_compat import Distribution
 from piptools.cache import DependencyCache
 from piptools.exceptions import NoCandidateFound
 from piptools.locations import DEFAULT_CONFIG_FILE_NAMES