This method should be a function in context.py

2 files changed, 36 insertions, 34 deletions

diff --git a/coverage/context.py b/coverage/context.py
index 25be98c5..22c0e531 100644
--- a/coverage/context.py
+++ b/coverage/context.py
@@ -3,6 +3,37 @@
 
 """Determine contexts for coverage.py"""
 
+
+def combine_context_switchers(context_switchers):
+    """Create a single context switcher from multiple switchers.
+
+    `context_switchers` is a list of functions that take a frame as an
+    argument and return a string to use as the new context label.
+
+    Returns a function that composites `context_switchers` functions, or None
+    if `context_switchers` is an empty list.
+
+    When invoked, the combined switcher calls `context_switchers` one-by-one
+    until a string is returned.  The combined switcher returns None if all
+    `context_switchers` return None.
+    """
+    if not context_switchers:
+        return None
+
+    if len(context_switchers) == 1:
+        return context_switchers[0]
+
+    def should_start_context(frame):
+        """The combiner for multiple context switchers."""
+        for switcher in context_switchers:
+            new_context = switcher(frame)
+            if new_context is not None:
+                return new_context
+        return None
+
+    return should_start_context
+
+
 def should_start_context_test_function(frame):
     """Is this frame calling a test_* function?"""
     if frame.f_code.co_name.startswith("test"):
diff --git a/coverage/control.py b/coverage/control.py
index ae5f0442..9bcab844 100644
--- a/coverage/control.py
+++ b/coverage/control.py
@@ -15,7 +15,7 @@ from coverage.annotate import AnnotateReporter
 from coverage.backward import string_class, iitems
 from coverage.collector import Collector, CTracer
 from coverage.config import read_coverage_config
-from coverage.context import should_start_context_test_function
+from coverage.context import should_start_context_test_function, combine_context_switchers
 from coverage.data import CoverageData, combine_parallel_data
 from coverage.debug import DebugControl, write_formatted_info
 from coverage.disposition import disposition_debug_msg
@@ -335,34 +335,6 @@ class Coverage(object):
         if not should_skip:
             self._data.read()
 
-    def _combine_context_switchers(self, context_switchers):
-        """Create a single context switcher from multiple switchers.
-
-        `context_switchers` is a list of methods that take a frame
-        as an argument and return a string to use as the new context label.
-
-        Returns a method that composits `context_switchers` methods, or None
-        if `context_switchers` is an empty list.
-
-        When invoked, the combined switcher calls `context_switchers` one-by-one
-        until a string is returned.  Combined switcher returns None if all
-        `context_switchers` return None.
-        """
-        if not context_switchers:
-            return None
-
-        if len(context_switchers) == 1:
-            return context_switchers[0]
-
-        def should_start_context(frame):
-            for switcher in context_switchers:
-                new_context = switcher(frame)
-                if new_context is not None:
-                    return new_context
-            return None
-
-        return should_start_context
-
     def _init_for_start(self):
         """Initialization for start()"""
         # Construct the collector.
@@ -386,12 +358,11 @@ class Coverage(object):
                 "Don't understand dynamic_context setting: {!r}".format(self.config.dynamic_context)
             )
 
-        context_switchers.extend([
-            plugin.dynamic_context
-            for plugin in self._plugins.context_switchers
-            ])
+        context_switchers.extend(
+            plugin.dynamic_context for plugin in self._plugins.context_switchers
+        )
 
-        should_start_context = self._combine_context_switchers(context_switchers)
+        should_start_context = combine_context_switchers(context_switchers)
 
         self._collector = Collector(
             should_trace=self._should_trace,