Move installation order code out of RequirementSet

src/pip/_internal/commands/install.py

@@ -14,7 +14,7 @@ from pip._internal.exceptions import (
 )
 from pip._internal.locations import distutils_scheme, virtualenv_no_global
 from pip._internal.operations.prepare import RequirementPreparer
-from pip._internal.req import RequirementSet
+from pip._internal.req import RequirementSet, install_given_reqs
 from pip._internal.resolve import Resolver
 from pip._internal.status_codes import ERROR
 from pip._internal.utils.filesystem import check_path_owner
@@ -292,7 +292,9 @@ class InstallCommand(RequirementCommand):
                             session=session, autobuilding=True
                         )
 
-                    installed = requirement_set.install(
+                    to_install = requirement_set.to_install()
+                    installed = install_given_reqs(
+                        to_install,
                         install_options,
                         global_options,
                         root=options.root_path,

src/pip/_internal/req/__init__.py

@@ -1,10 +1,68 @@
 from __future__ import absolute_import
 
+import logging
+
 from .req_install import InstallRequirement
 from .req_set import RequirementSet
 from .req_file import parse_requirements
+from pip._internal.utils.logging import indent_log
+
 
 __all__ = [
     "RequirementSet", "InstallRequirement",
-    "parse_requirements",
+    "parse_requirements", "install_req_set",
 ]
+
+logger = logging.getLogger(__name__)
+
+def install_given_reqs(to_install, install_options, global_options=(),
+                       *args, **kwargs):
+    """
+    Install everything in the given list.
+
+    (to be called after having downloaded and unpacked the packages)
+    """
+
+    if to_install:
+        logger.info(
+            'Installing collected packages: %s',
+            ', '.join([req.name for req in to_install]),
+        )
+
+    with indent_log():
+        for requirement in to_install:
+            if requirement.conflicts_with:
+                logger.info(
+                    'Found existing installation: %s',
+                    requirement.conflicts_with,
+                )
+                with indent_log():
+                    uninstalled_pathset = requirement.uninstall(
+                        auto_confirm=True
+                    )
+            try:
+                requirement.install(
+                    install_options,
+                    global_options,
+                    *args,
+                    **kwargs
+                )
+            except:
+                should_rollback = (
+                    requirement.conflicts_with and
+                    not requirement.install_succeeded
+                )
+                # if install did not succeed, rollback previous uninstall
+                if should_rollback:
+                    uninstalled_pathset.rollback()
+                raise
+            else:
+                should_commit = (
+                    requirement.conflicts_with and
+                    requirement.install_succeeded
+                )
+                if should_commit:
+                    uninstalled_pathset.commit()
+            requirement.remove_temporary_source()
+
+    return to_install

src/pip/_internal/req/req_set.py

@@ -33,6 +33,7 @@ class RequirementSet(object):
         self.target_dir = target_dir  # set from --target option
         self.pycompile = pycompile
         # Maps from install_req -> dependencies_of_install_req
+        # XXX: Move into resolver
         self._dependencies = defaultdict(list)
 
     def __str__(self):
@@ -169,7 +170,8 @@ class RequirementSet(object):
             for req in self.reqs_to_cleanup:
                 req.remove_temporary_source()
 
-    def _to_install(self):
+    def to_install(self):
+        # XXX: Move into resolver
         """Create the installation order.
 
         The installation order is topological - requirements are installed
@@ -195,54 +197,3 @@ class RequirementSet(object):
         for install_req in self.requirements.values():
             schedule(install_req)
         return order
-
-    def install(self, install_options, global_options=(), *args, **kwargs):
-        """
-        Install everything in this set (after having downloaded and unpacked
-        the packages)
-        """
-        to_install = self._to_install()
-
-        if to_install:
-            logger.info(
-                'Installing collected packages: %s',
-                ', '.join([req.name for req in to_install]),
-            )
-
-        with indent_log():
-            for requirement in to_install:
-                if requirement.conflicts_with:
-                    logger.info(
-                        'Found existing installation: %s',
-                        requirement.conflicts_with,
-                    )
-                    with indent_log():
-                        uninstalled_pathset = requirement.uninstall(
-                            auto_confirm=True
-                        )
-                try:
-                    requirement.install(
-                        install_options,
-                        global_options,
-                        *args,
-                        **kwargs
-                    )
-                except:
-                    should_rollback = (
-                        requirement.conflicts_with and
-                        not requirement.install_succeeded
-                    )
-                    # if install did not succeed, rollback previous uninstall
-                    if should_rollback:
-                        uninstalled_pathset.rollback()
-                    raise
-                else:
-                    should_commit = (
-                        requirement.conflicts_with and
-                        requirement.install_succeeded
-                    )
-                    if should_commit:
-                        uninstalled_pathset.commit()
-                requirement.remove_temporary_source()
-
-        return to_install