Deprecate setup.py install fallback when wheel package is absent

news/8559.removal.rst

@@ -0,0 +1,2 @@
+Deprecate installation with 'setup.py install' when the 'wheel' package is absent for
+source distributions without 'pyproject.toml'.

src/pip/_internal/commands/install.py

@@ -29,6 +29,7 @@
 from pip._internal.req import install_given_reqs
 from pip._internal.req.req_install import InstallRequirement
 from pip._internal.utils.compat import WINDOWS
+from pip._internal.utils.deprecation import LegacyInstallReasonFailedBdistWheel
 from pip._internal.utils.distutils_args import parse_distutils_args
 from pip._internal.utils.filesystem import test_writable_dir
 from pip._internal.utils.logging import getLogger
@@ -440,7 +441,7 @@ def run(self, options: Values, args: List[str]) -> int:
             # those.
             for r in build_failures:
                 if not r.use_pep517:
-                    r.legacy_install_reason = 8368
+                    r.legacy_install_reason = LegacyInstallReasonFailedBdistWheel
 
             to_install = resolver.get_installation_order(requirement_set)
 

src/pip/_internal/req/req_install.py

@@ -42,7 +42,7 @@
 from pip._internal.operations.install.wheel import install_wheel
 from pip._internal.pyproject import load_pyproject_toml, make_pyproject_path
 from pip._internal.req.req_uninstall import UninstallPathSet
-from pip._internal.utils.deprecation import deprecated
+from pip._internal.utils.deprecation import LegacyInstallReason, deprecated
 from pip._internal.utils.direct_url_helpers import (
     direct_url_for_editable,
     direct_url_from_link,
@@ -96,7 +96,7 @@ def __init__(
         self.constraint = constraint
         self.editable = editable
         self.permit_editable_wheels = permit_editable_wheels
-        self.legacy_install_reason: Optional[int] = None
+        self.legacy_install_reason: Optional[LegacyInstallReason] = None
 
         # source_dir is the local directory where the linked requirement is
         # located, or unpacked. In case unpacking is needed, creating and
@@ -811,6 +811,11 @@ def install(
         install_options = list(install_options) + self.install_options
 
         try:
+            if (
+                self.legacy_install_reason is not None
+                and self.legacy_install_reason.emit_before_install
+            ):
+                self.legacy_install_reason.emit_deprecation(self.name)
             success = install_legacy(
                 install_options=install_options,
                 global_options=global_options,
@@ -836,18 +841,12 @@ def install(
 
         self.install_succeeded = success
 
-        if success and self.legacy_install_reason == 8368:
-            deprecated(
-                reason=(
-                    "{} was installed using the legacy 'setup.py install' "
-                    "method, because a wheel could not be built for it.".format(
-                        self.name
-                    )
-                ),
-                replacement="to fix the wheel build issue reported above",
-                gone_in=None,
-                issue=8368,
-            )
+        if (
+            success
+            and self.legacy_install_reason is not None
+            and self.legacy_install_reason.emit_after_success
+        ):
+            self.legacy_install_reason.emit_deprecation(self.name)
 
 
 def check_invalid_constraint_type(req: InstallRequirement) -> str:

src/pip/_internal/utils/deprecation.py

@@ -118,3 +118,58 @@ def deprecated(
         raise PipDeprecationWarning(message)
 
     warnings.warn(message, category=PipDeprecationWarning, stacklevel=2)
+
+
+class LegacyInstallReason:
+    def __init__(
+        self,
+        reason: str,
+        replacement: Optional[str],
+        gone_in: Optional[str],
+        feature_flag: Optional[str] = None,
+        issue: Optional[int] = None,
+        emit_after_success: bool = False,
+        emit_before_install: bool = False,
+    ):
+        self._reason = reason
+        self._replacement = replacement
+        self._gone_in = gone_in
+        self._feature_flag = feature_flag
+        self._issue = issue
+        self.emit_after_success = emit_after_success
+        self.emit_before_install = emit_before_install
+
+    def emit_deprecation(self, name: str) -> None:
+        deprecated(
+            reason=self._reason.format(name=name),
+            replacement=self._replacement,
+            gone_in=self._gone_in,
+            feature_flag=self._feature_flag,
+            issue=self._issue,
+        )
+
+
+LegacyInstallReasonFailedBdistWheel = LegacyInstallReason(
+    reason=(
+        "{name} was installed using the legacy 'setup.py install' "
+        "method, because a wheel could not be built for it."
+    ),
+    replacement="to fix the wheel build issue reported above",
+    gone_in=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=None,
+    issue=8559,
+    emit_before_install=True,
+)

src/pip/_internal/wheel_builder.py

@@ -19,6 +19,7 @@
 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.setuptools_build import make_setuptools_clean_args
@@ -86,11 +87,7 @@ def _should_build(
 
     if not is_wheel_installed():
         # we don't build legacy requirements if wheel is not installed
-        logger.info(
-            "Using legacy 'setup.py install' for %s, "
-            "since package 'wheel' is not installed.",
-            req.name,
-        )
+        req.legacy_install_reason = LegacyInstallReasonMissingWheelPackage
         return False
 
     return True

tests/functional/test_install.py

@@ -12,6 +12,7 @@
 
 from pip._internal.cli.status_codes import ERROR, SUCCESS
 from pip._internal.models.index import PyPI, TestPyPI
+from pip._internal.utils.deprecation import DEPRECATION_MSG_PREFIX
 from pip._internal.utils.misc import rmtree
 from tests.conftest import CertFactory
 from tests.lib import (
@@ -2286,3 +2287,32 @@ def test_install_dry_run(script: PipTestEnvironment, data: TestData) -> None:
     )
     assert "Would install simple-3.0" in result.stdout
     assert "Successfully installed" not in result.stdout
+
+
+def test_install_8559_missing_wheel_package(
+    script: PipTestEnvironment, shared_data: TestData
+) -> None:
+    result = script.pip(
+        "install",
+        "--find-links",
+        shared_data.find_links,
+        "simple",
+        allow_stderr_warning=True,
+    )
+    assert DEPRECATION_MSG_PREFIX in result.stderr
+    assert "'wheel' package is not installed" in result.stderr
+    assert "using the legacy 'setup.py install' method" in result.stderr
+
+
+@pytest.mark.usefixtures("with_wheel")
+def test_install_8559_wheel_package_present(
+    script: PipTestEnvironment, shared_data: TestData
+) -> None:
+    result = script.pip(
+        "install",
+        "--find-links",
+        shared_data.find_links,
+        "simple",
+        allow_stderr_warning=False,
+    )
+    assert DEPRECATION_MSG_PREFIX not in result.stderr

tests/functional/test_install_index.py

@@ -23,6 +23,7 @@ def test_find_links_relative_path(script: PipTestEnvironment, data: TestData) ->
     result.did_create(initools_folder)
 
 
+@pytest.mark.usefixtures("with_wheel")
 def test_find_links_no_doctype(script: PipTestEnvironment, data: TestData) -> None:
     shutil.copy(data.packages / "simple-1.0.tar.gz", script.scratch_path)
     html = script.scratch_path.joinpath("index.html")