Allow plugins to alter the paths config

Signed-off-by: Bernat Gabor <bgabor8@bloomberg.net>

coverage/config.py

@@ -421,6 +421,9 @@ def set_option(self, option_name, value):
         `value` is the new value for the option.
 
         """
+        if option_name == "paths":
+            self.paths = value
+            return
 
         # Check all the hard-coded options.
         for option_spec in self.CONFIG_FILE_OPTIONS:
@@ -448,6 +451,9 @@ def get_option(self, option_name):
         Returns the value of the option.
 
         """
+        if option_name == "paths":
+            return self.paths
+
         # Check all the hard-coded options.
         for option_spec in self.CONFIG_FILE_OPTIONS:
             attr, where = option_spec[:2]

tests/test_config.py

@@ -3,6 +3,7 @@
 # For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
 
 """Test the config file handling for coverage.py"""
+from collections import OrderedDict
 
 import mock
 
@@ -340,6 +341,17 @@ def test_tweaks_after_constructor(self):
         self.assertFalse(cov.get_option("run:branch"))
         self.assertEqual(cov.get_option("run:data_file"), "fooey.dat")
 
+    def test_tweaks_paths_after_constructor(self):
+        cov = coverage.Coverage()
+        paths = cov.get_option("paths")
+        self.assertEqual(paths, OrderedDict())
+
+        new_paths = OrderedDict()
+        new_paths['magic'] = ['src', 'ok']
+        cov.set_option("paths", new_paths)
+
+        self.assertEqual(cov.get_option("paths"), new_paths)
+
     def test_tweak_error_checking(self):
         # Trying to set an unknown config value raises an error.
         cov = coverage.Coverage()