Always use pep 517 when the 'wheel' package is absent

Author: sbidoul

news/8559.removal.rst

@@ -0,0 +1,2 @@
+When the ``wheel`` package is not installed, pip now uses the default build backend
+instead of ``setup.py install`` for project without ``pyproject.toml``.

src/pip/_internal/cli/cmdoptions.py

@@ -783,11 +783,15 @@ def _handle_no_use_pep517(
         """
         raise_option_error(parser, option=option, msg=msg)
 
-    # If user doesn't wish to use pep517, we check if setuptools is installed
+    # If user doesn't wish to use pep517, we check if setuptools and wheel are installed
     # and raise error if it is not.
-    if not importlib.util.find_spec("setuptools"):
-        msg = "It is not possible to use --no-use-pep517 without setuptools installed."
-        raise_option_error(parser, option=option, msg=msg)
+    for package in ("setuptools", "wheel"):
+        if not importlib.util.find_spec(package):
+            msg = (
+                f"It is not possible to use --no-use-pep517 "
+                f"without {package} installed."
+            )
+            raise_option_error(parser, option=option, msg=msg)
 
     # Otherwise, --no-use-pep517 was passed via the command-line.
     parser.values.use_pep517 = False

src/pip/_internal/pyproject.py

@@ -93,12 +93,17 @@ def load_pyproject_toml(
     # we do so if the project has a pyproject.toml file
     # or if we cannot import setuptools.
 
-    # We fallback to PEP 517 when without setuptools,
+    # We fallback to PEP 517 when without setuptools or without the wheel package,
     # so setuptools can be installed as a default build backend.
     # For more info see:
     # https://discuss.python.org/t/pip-without-setuptools-could-the-experience-be-improved/11810/9
+    # https://github.com/pypa/pip/issues/8559
     elif use_pep517 is None:
-        use_pep517 = has_pyproject or not importlib.util.find_spec("setuptools")
+        use_pep517 = (
+            has_pyproject
+            or not importlib.util.find_spec("setuptools")
+            or not importlib.util.find_spec("wheel")
+        )
 
     # At this point, we know whether we're going to use PEP 517.
     assert use_pep517 is not None

src/pip/_internal/utils/deprecation.py

@@ -159,17 +159,3 @@ def emit_deprecation(self, name: str) -> None:
     issue=8368,
     emit_after_success=True,
 )
-
-
-LegacyInstallReasonMissingWheelPackage = LegacyInstallReason(
-    reason=(
-        "{name} is being installed using the legacy "
-        "'setup.py install' method, because it does not have a "
-        "'pyproject.toml' and the 'wheel' package "
-        "is not installed."
-    ),
-    replacement="to enable the '--use-pep517' option",
-    gone_in="23.1",
-    issue=8559,
-    emit_before_install=True,
-)

src/pip/_internal/utils/misc.py

@@ -614,18 +614,6 @@ def hash_file(path: str, blocksize: int = 1 << 20) -> Tuple[Any, int]:
     return h, length
 
 
-def is_wheel_installed() -> bool:
-    """
-    Return whether the wheel package is installed.
-    """
-    try:
-        import wheel  # noqa: F401
-    except ImportError:
-        return False
-
-    return True
-
-
 def pairwise(iterable: Iterable[Any]) -> Iterator[Tuple[Any, Any]]:
     """
     Return paired elements.

src/pip/_internal/wheel_builder.py

@@ -19,9 +19,8 @@
 from pip._internal.operations.build.wheel_editable import build_wheel_editable
 from pip._internal.operations.build.wheel_legacy import build_wheel_legacy
 from pip._internal.req.req_install import InstallRequirement
-from pip._internal.utils.deprecation import LegacyInstallReasonMissingWheelPackage
 from pip._internal.utils.logging import indent_log
-from pip._internal.utils.misc import ensure_dir, hash_file, is_wheel_installed
+from pip._internal.utils.misc import ensure_dir, hash_file
 from pip._internal.utils.setuptools_build import make_setuptools_clean_args
 from pip._internal.utils.subprocess import call_subprocess
 from pip._internal.utils.temp_dir import TempDirectory
@@ -73,14 +72,6 @@ def _should_build(
         # we only build PEP 660 editable requirements
         return req.supports_pyproject_editable()
 
-    if req.use_pep517:
-        return True
-
-    if not is_wheel_installed():
-        # we don't build legacy requirements if wheel is not installed
-        req.legacy_install_reason = LegacyInstallReasonMissingWheelPackage
-        return False
-
     return True
 
 

tests/unit/test_wheel_builder.py

@@ -2,7 +2,6 @@
 import os
 from pathlib import Path
 from typing import Optional, cast
-from unittest import mock
 
 import pytest
 
@@ -117,26 +116,6 @@ def test_should_build_for_wheel_command(req: ReqMock, expected: bool) -> None:
     assert should_build is expected
 
 
-@mock.patch("pip._internal.wheel_builder.is_wheel_installed")
-def test_should_build_legacy_wheel_not_installed(is_wheel_installed: mock.Mock) -> None:
-    is_wheel_installed.return_value = False
-    legacy_req = ReqMock(use_pep517=False)
-    should_build = wheel_builder.should_build_for_install_command(
-        cast(InstallRequirement, legacy_req),
-    )
-    assert not should_build
-
-
-@mock.patch("pip._internal.wheel_builder.is_wheel_installed")
-def test_should_build_legacy_wheel_installed(is_wheel_installed: mock.Mock) -> None:
-    is_wheel_installed.return_value = True
-    legacy_req = ReqMock(use_pep517=False)
-    should_build = wheel_builder.should_build_for_install_command(
-        cast(InstallRequirement, legacy_req),
-    )
-    assert should_build
-
-
 @pytest.mark.parametrize(
     "req, expected",
     [