Don't fallback to setup.py install when build failed

Author: sbidoul

news/8368.removal.rst

@@ -0,0 +1,2 @@
+Remove ``setup.py install`` fallback when building a wheel failed for projects without
+``pyproject.toml``.

src/pip/_internal/commands/install.py

@@ -30,7 +30,6 @@
     check_legacy_setup_py_options,
 )
 from pip._internal.utils.compat import WINDOWS
-from pip._internal.utils.deprecation import LegacyInstallReasonFailedBdistWheel
 from pip._internal.utils.filesystem import test_writable_dir
 from pip._internal.utils.logging import getLogger
 from pip._internal.utils.misc import (
@@ -423,26 +422,14 @@ def run(self, options: Values, args: List[str]) -> int:
                 global_options=global_options,
             )
 
-            # If we're using PEP 517, we cannot do a legacy setup.py install
-            # so we fail here.
-            pep517_build_failure_names: List[str] = [
-                r.name for r in build_failures if r.use_pep517  # type: ignore
-            ]
-            if pep517_build_failure_names:
+            if build_failures:
                 raise InstallationError(
                     "Could not build wheels for {}, which is required to "
                     "install pyproject.toml-based projects".format(
-                        ", ".join(pep517_build_failure_names)
+                        ", ".join(r.name for r in build_failures)  # type: ignore
                     )
                 )
 
-            # For now, we just warn about failures building legacy
-            # requirements, as we'll fall through to a setup.py install for
-            # those.
-            for r in build_failures:
-                if not r.use_pep517:
-                    r.legacy_install_reason = LegacyInstallReasonFailedBdistWheel
-
             to_install = resolver.get_installation_order(requirement_set)
 
             # Check for conflicts in the package set we're installing.

src/pip/_internal/utils/deprecation.py

@@ -147,15 +147,3 @@ def emit_deprecation(self, name: str) -> None:
             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="23.1",
-    issue=8368,
-    emit_after_success=True,
-)