CI pep8, flake8, mypy, py27

Author: bmartinn

news/8187.feature

@@ -1,3 +1,5 @@
-Run the wheel install in a multiprocessing Pool, this has x1.5 speedup factor when installing cached packages.
-Packages that could not be installed (exception raised), will be installed serially once the Pool is done.
-If multiprocessing.Pool is not supported by the platform, fall-back to serial installation.
+Run the wheel install in a multiprocessing Pool, this has x1.5 speedup factor
+when installing cached packages. Packages that could not be installed
+(exception raised), will be installed serially once the Pool is done.
+If multiprocessing.Pool is not supported by the platform,
+fall-back to serial installation.

src/pip/_internal/req/__init__.py

@@ -4,6 +4,7 @@
 from __future__ import absolute_import
 
 import logging
+from functools import partial
 
 from pip._internal.utils.logging import indent_log
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
@@ -13,12 +14,12 @@
 from .req_set import RequirementSet
 
 try:
-    from multiprocessing.pool import Pool
+    from multiprocessing.pool import Pool  # noqa
 except ImportError:  # Platform-specific: No multiprocessing available
-    Pool = None
+    Pool = None   # type: ignore
 
 if MYPY_CHECK_RUNNING:
-    from typing import Any, List, Sequence
+    from typing import Any, List, Sequence, Optional
 
 __all__ = [
     "RequirementSet", "InstallRequirement",
@@ -59,64 +60,71 @@ def install_given_reqs(
         )
 
     # pre allocate installed package names
-    installed = [None] * len(to_install)
+    installed = \
+        [None] * len(to_install)  # type: List[Optional[InstallationResult]]
+
     install_args = [install_options, global_options, args, kwargs]
 
-    if Pool is not None:
+    if to_install and Pool is not None:
         # first let's try to install in parallel, if we fail we do it by order.
         pool = Pool()
         try:
-            pool_result = pool.starmap_async(__single_install, [(install_args, r) for r in to_install])
+            pool_result = pool.map_async(
+                partial(__single_install, install_args), to_install)
             # python 2.7 timeout=None will not catch KeyboardInterrupt
             installed = pool_result.get(timeout=999999)
         except (KeyboardInterrupt, SystemExit):
             pool.terminate()
             raise
-        except Exception:
-            # we will reinstall sequentially
-            pass
         pool.close()
         pool.join()
 
     with indent_log():
         for i, requirement in enumerate(to_install):
             if installed[i] is None:
-                installed[i] = __single_install(install_args, requirement, allow_raise=True)
+                installed[i] = __single_install(
+                    install_args, requirement, allow_raise=True)
 
     return [i for i in installed if i is not None]
 
 
-def __single_install(args, a_requirement, allow_raise=False):
-    if a_requirement.should_reinstall:
-        logger.info('Attempting uninstall: %s', a_requirement.name)
+def __single_install(
+        install_args,      # type: List[Any]
+        requirement,       # type: InstallRequirement
+        allow_raise=False  # type: bool
+):
+    # type: (...) -> Optional[InstallationResult]
+    """
+    Install a single requirement, returns InstallationResult
+
+    (to be called per requirement, either in parallel or serially)
+    """
+    if requirement.should_reinstall:
+        logger.info('Attempting uninstall: %s', requirement.name)
         with indent_log():
-            uninstalled_pathset = a_requirement.uninstall(
+            uninstalled_pathset = requirement.uninstall(
                 auto_confirm=True
             )
     try:
-        a_requirement.install(
-            args[0],   # install_options,
-            args[1],   # global_options,
-            *args[2],  # *args,
-            **args[3]  # **kwargs
+        requirement.install(
+            install_args[0],   # install_options,
+            install_args[1],   # global_options,
+            *install_args[2],  # *args,
+            **install_args[3]  # **kwargs
         )
     except Exception:
-        should_rollback = (
-                a_requirement.should_reinstall and
-                not a_requirement.install_succeeded
-        )
+        should_rollback = (requirement.should_reinstall and
+                           not requirement.install_succeeded)
         # if install did not succeed, rollback previous uninstall
         if should_rollback:
             uninstalled_pathset.rollback()
         if allow_raise:
             raise
     else:
-        should_commit = (
-                a_requirement.should_reinstall and
-                a_requirement.install_succeeded
-        )
+        should_commit = (requirement.should_reinstall and
+                         requirement.install_succeeded)
         if should_commit:
             uninstalled_pathset.commit()
-        return InstallationResult(a_requirement.name)
+        return InstallationResult(requirement.name)
 
     return None