Refactor legacy_install_reason

Author: sbidoul

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
@@ -836,18 +836,12 @@ 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 +118,44 @@ 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,
+)