Fail command lines that use multiprocessing and other options together. #495

3 files changed, 35 insertions, 0 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 3320bfe..5ee9612 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -5,6 +5,20 @@
 Change history for Coverage.py
 ==============================
 
+Unreleased
+----------
+
+- Since ``concurrency=multiprocessing`` uses subprocesses, options specified on
+  the coverage.py command line will not be communicated down to them.  Only
+  options in the configuration file will apply to the subprocesses.
+  Previously, the options didn't apply to the subprocesses, but there was no
+  indication.  Now it is an error to use ``--concurrency=multiprocessing`` and
+  other run-affecting options on the command line.  This prevents
+  failures like those reported in `issue 495`_.
+
+.. _issue 495: https://bitbucket.org/ned/coveragepy/issues/495/branch-and-concurrency-are-conflicting
+
+
 Version 4.2b1 --- 2016-07-04
 ----------------------------
 
diff --git a/coverage/cmdline.py b/coverage/cmdline.py
index e530640..20d3589 100644
--- a/coverage/cmdline.py
+++ b/coverage/cmdline.py
@@ -602,6 +602,17 @@ class CoverageScript(object):
             self.help_fn("Can't append to data files in parallel mode.")
             return ERR
 
+        if options.concurrency == "multiprocessing":
+            # Can't set other run-affecting command line options with
+            # multiprocessing.
+            for opt_name in ['branch', 'include', 'omit', 'pylib', 'source', 'timid']:
+                if getattr(options, opt_name) != getattr(Opts, opt_name).default:
+                    self.help_fn(
+                        "Options affecting multiprocessing must be specified "
+                        "in a configuration file."
+                    )
+                    return ERR
+
         if not self.coverage.get_option("run:parallel"):
             if not options.append:
                 self.coverage.erase()
diff --git a/tests/test_cmdline.py b/tests/test_cmdline.py
index d72fd83..f253160 100644
--- a/tests/test_cmdline.py
+++ b/tests/test_cmdline.py
@@ -464,6 +464,16 @@ class CmdLineTest(BaseCmdLineTest):
         out = self.stdout()
         self.assertIn("option --concurrency: invalid choice: 'multiprocessing,gevent'", out)
 
+    def test_multiprocessing_needs_config_file(self):
+        # You can't use command-line args to add options to multiprocessing
+        # runs, since they won't make it to the subprocesses. You need to use a
+        # config file.
+        self.command_line("run --concurrency=multiprocessing --branch foo.py", ret=ERR)
+        self.assertIn(
+            "Options affecting multiprocessing must be specified in a configuration file.",
+            self.stdout()
+        )
+
     def test_run_debug(self):
         self.cmd_executes("run --debug=opt1 foo.py", """\
             .coverage(debug=["opt1"])