Make the WheelCache FormatControl argument optional

This commit does not change behaviour, but makes the fact
that --no-binary does not disable the cache anymore (when
always-install-via-wheel is set) more explicit.

Author: sbidoul

src/pip/_internal/cache.py

@@ -231,8 +231,10 @@ class WheelCache(Cache):
     when a certain link is not found in the simple wheel cache first.
     """
 
-    def __init__(self, cache_dir, format_control):
-        # type: (str, FormatControl) -> None
+    def __init__(self, cache_dir, format_control=None):
+        # type: (str, Optional[FormatControl]) -> None
+        if format_control is None:
+            format_control = FormatControl()
         super().__init__(cache_dir, format_control, {'binary'})
         self._wheel_cache = SimpleWheelCache(cache_dir, format_control)
         self._ephem_cache = EphemWheelCache(format_control)

src/pip/_internal/commands/install.py

@@ -275,7 +275,12 @@ def run(self, options, args):
             target_python=target_python,
             ignore_requires_python=options.ignore_requires_python,
         )
-        wheel_cache = WheelCache(options.cache_dir, options.format_control)
+        if "always-install-via-wheel" in options.features_enabled:
+            wheel_cache = WheelCache(options.cache_dir)
+        else:
+            # TODO when removing this branch, also remove format control support
+            #      in WheelCache.
+            wheel_cache = WheelCache(options.cache_dir, options.format_control)
 
         req_tracker = self.enter_context(get_requirement_tracker())
 

src/pip/_internal/commands/wheel.py

@@ -103,7 +103,12 @@ def run(self, options, args):
         session = self.get_default_session(options)
 
         finder = self._build_package_finder(options, session)
-        wheel_cache = WheelCache(options.cache_dir, options.format_control)
+        if "always-install-via-wheel" in options.features_enabled:
+            wheel_cache = WheelCache(options.cache_dir)
+        else:
+            # TODO when removing this branch, also remove format control support
+            #      in WheelCache.
+            wheel_cache = WheelCache(options.cache_dir, options.format_control)
 
         options.wheel_dir = normalize_path(options.wheel_dir)
         ensure_dir(options.wheel_dir)