Add make_requirement_preparer() to RequirementCommand base class (#6810)

src/pip/_internal/cli/base_command.py

@@ -33,6 +33,7 @@ from pip._internal.exceptions import (
 from pip._internal.index import PackageFinder
 from pip._internal.models.selection_prefs import SelectionPreferences
 from pip._internal.models.target_python import TargetPython
+from pip._internal.operations.prepare import RequirementPreparer
 from pip._internal.req.constructors import (
     install_req_from_editable,
     install_req_from_line,
@@ -50,6 +51,8 @@ if MYPY_CHECK_RUNNING:
     from optparse import Values
     from pip._internal.cache import WheelCache
     from pip._internal.req.req_set import RequirementSet
+    from pip._internal.req.req_tracker import RequirementTracker
+    from pip._internal.utils.temp_dir import TempDirectory
 
 __all__ = ['Command']
 
@@ -257,6 +260,28 @@ class Command(object):
 
 class RequirementCommand(Command):
 
+    @staticmethod
+    def make_requirement_preparer(
+            temp_directory,           # type: TempDirectory
+            options,                  # type: Values
+            req_tracker,              # type: RequirementTracker
+            download_dir=None,        # type: str
+            wheel_download_dir=None,  # type: str
+    ):
+        # type: (...) -> RequirementPreparer
+        """
+        Create a RequirementPreparer instance for the given parameters.
+        """
+        return RequirementPreparer(
+            build_dir=temp_directory.path,
+            src_dir=options.src_dir,
+            download_dir=download_dir,
+            wheel_download_dir=wheel_download_dir,
+            progress_bar=options.progress_bar,
+            build_isolation=options.build_isolation,
+            req_tracker=req_tracker,
+        )
+
     @staticmethod
     def populate_requirement_set(requirement_set,  # type: RequirementSet
                                  args,             # type: List[str]

src/pip/_internal/commands/download.py

@@ -7,7 +7,6 @@ from pip._internal.cli import cmdoptions
 from pip._internal.cli.base_command import RequirementCommand
 from pip._internal.cli.cmdoptions import make_target_python
 from pip._internal.legacy_resolve import Resolver
-from pip._internal.operations.prepare import RequirementPreparer
 from pip._internal.req import RequirementSet
 from pip._internal.req.req_tracker import RequirementTracker
 from pip._internal.utils.filesystem import check_path_owner
@@ -126,14 +125,11 @@ class DownloadCommand(RequirementCommand):
                     None
                 )
 
-                preparer = RequirementPreparer(
-                    build_dir=directory.path,
-                    src_dir=options.src_dir,
-                    download_dir=options.download_dir,
-                    wheel_download_dir=None,
-                    progress_bar=options.progress_bar,
-                    build_isolation=options.build_isolation,
+                preparer = self.make_requirement_preparer(
+                    temp_directory=directory,
+                    options=options,
                     req_tracker=req_tracker,
+                    download_dir=options.download_dir,
                 )
 
                 resolver = Resolver(

src/pip/_internal/commands/install.py

@@ -22,7 +22,6 @@ from pip._internal.exceptions import (
 from pip._internal.legacy_resolve import Resolver
 from pip._internal.locations import distutils_scheme
 from pip._internal.operations.check import check_install_conflicts
-from pip._internal.operations.prepare import RequirementPreparer
 from pip._internal.req import RequirementSet, install_given_reqs
 from pip._internal.req.req_tracker import RequirementTracker
 from pip._internal.utils.filesystem import check_path_owner
@@ -322,16 +321,11 @@ class InstallCommand(RequirementCommand):
                         requirement_set, args, options, finder, session,
                         self.name, wheel_cache
                     )
-                    preparer = RequirementPreparer(
-                        build_dir=directory.path,
-                        src_dir=options.src_dir,
-                        download_dir=None,
-                        wheel_download_dir=None,
-                        progress_bar=options.progress_bar,
-                        build_isolation=options.build_isolation,
+                    preparer = self.make_requirement_preparer(
+                        temp_directory=directory,
+                        options=options,
                         req_tracker=req_tracker,
                     )
-
                     resolver = Resolver(
                         preparer=preparer,
                         finder=finder,

src/pip/_internal/commands/wheel.py

@@ -9,7 +9,6 @@ from pip._internal.cli import cmdoptions
 from pip._internal.cli.base_command import RequirementCommand
 from pip._internal.exceptions import CommandError, PreviousBuildDirError
 from pip._internal.legacy_resolve import Resolver
-from pip._internal.operations.prepare import RequirementPreparer
 from pip._internal.req import RequirementSet
 from pip._internal.req.req_tracker import RequirementTracker
 from pip._internal.utils.temp_dir import TempDirectory
@@ -129,14 +128,11 @@ class WheelCommand(RequirementCommand):
                         self.name, wheel_cache
                     )
 
-                    preparer = RequirementPreparer(
-                        build_dir=directory.path,
-                        src_dir=options.src_dir,
-                        download_dir=None,
-                        wheel_download_dir=options.wheel_dir,
-                        progress_bar=options.progress_bar,
-                        build_isolation=options.build_isolation,
+                    preparer = self.make_requirement_preparer(
+                        temp_directory=directory,
+                        options=options,
                         req_tracker=req_tracker,
+                        wheel_download_dir=options.wheel_dir,
                     )
 
                     resolver = Resolver(