Read options from tox.iniissue-519

If coveragerc does not exist, setup.cfg does not exist or does not
contain any coverage-related metadata, and no custom config file is
provided, fall back to tox.ini.

The syntax of tox.ini files is the same as that expected of setup.cfg
files, namely:

    [coverage:{section}]

Fixes: #519

3 files changed, 78 insertions, 26 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 1ff0dbb..e19085d 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -53,11 +53,16 @@ Unreleased
 
 - Support PyPy3 5.2 alpha 1.
 
+- Options are now also read from a tox.ini file, if any. Like setup.py,
+  sections are prefixed with "coverage:", so the ``[run]`` options will be read
+  from ``[coverage:run]`` section of tox.ini. Finishes `issue 519`_.
+
 .. _issue 412: https://bitbucket.org/ned/coveragepy/issues/412/coverage-combine-should-error-if-no
 .. _issue 505: https://bitbucket.org/ned/coveragepy/issues/505/use-canonical-filename-for-debounce
 .. _issue 510: https://bitbucket.org/ned/coveragepy/issues/510/erase-still-needed-in-42
 .. _issue 511: https://bitbucket.org/ned/coveragepy/issues/511/version-42-coverage-combine-empties
 .. _issue 516: https://bitbucket.org/ned/coveragepy/issues/516/running-coverage-combine-twice-deletes-all
+.. _issue 519: https://bitbucket.org/ned/coveragepy/issues/519/coverage-run-sections-in-toxini-or-as
 .. _issue 525: https://bitbucket.org/ned/coveragepy/issues/525/coverage-combine-when-not-in-parallel-mode
 .. _issue 529: https://bitbucket.org/ned/coveragepy/issues/529/encoding-marker-may-only-appear-on-the
 .. _issue 530: https://bitbucket.org/ned/coveragepy/issues/530/deprecationwarning-you-passed-a-bytestring
diff --git a/coverage/control.py b/coverage/control.py
index d920337..e658ef1 100644
--- a/coverage/control.py
+++ b/coverage/control.py
@@ -134,10 +134,8 @@ class Coverage(object):
         # 1: defaults:
         self.config = CoverageConfig()
 
-        # 2: from the rcfile, .coveragerc or setup.cfg file:
+        # 2: from the rcfile, .coveragerc, .tox or setup.cfg file:
         if config_file:
-            # pylint: disable=redefined-variable-type
-            did_read_rc = False
             # Some API users were specifying ".coveragerc" to mean the same as
             # True, so make it so.
             if config_file == ".coveragerc":
@@ -147,14 +145,22 @@ class Coverage(object):
                 config_file = ".coveragerc"
             self.config_file = config_file
 
-            did_read_rc = self.config.from_file(config_file)
+            for fname, prefix in [(config_file, ""),
+                                  ("setup.cfg", "coverage:"),
+                                  ("tox.ini", "coverage:")]:
+                config_read = self.config.from_file(fname,
+                                                    section_prefix=prefix)
+                print('config read?')
+                print(config_read)
+                is_config_file = fname == config_file
 
-            if not did_read_rc:
-                if specified_file:
+                if not config_read and is_config_file and specified_file:
                     raise CoverageException(
-                        "Couldn't read '%s' as a config file" % config_file
+                        "Couldn't read '%s' as a config file" % fname
                         )
-                self.config.from_file("setup.cfg", section_prefix="coverage:")
+
+                if config_read:
+                    break
 
         # 3: from environment variables:
         env_data_file = os.environ.get('COVERAGE_FILE')
diff --git a/tests/test_config.py b/tests/test_config.py
index 1c980b8..b45b89b 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -211,13 +211,15 @@ class ConfigTest(CoverageTest):
             _ = coverage.Coverage()
 
     def test_unknown_option_in_other_ini_file(self):
-        self.make_file("setup.cfg", """\
-            [coverage:run]
-            huh = what?
-            """)
-        msg = r"Unrecognized option '\[coverage:run\] huh=' in config file setup.cfg"
-        with self.assertRaisesRegex(CoverageException, msg):
-            _ = coverage.Coverage()
+        for fname in ["setup.cfg", "tox.ini"]:
+            self.make_file(fname, """\
+                [coverage:run]
+                huh = what?
+                """)
+            msg = (r"Unrecognized option '\[coverage:run\] huh=' in config "
+                   r"file %s" % fname)
+            with self.assertRaisesRegex(CoverageException, msg):
+                _ = coverage.Coverage()
 
 
 class ConfigFileTest(CoverageTest):
@@ -304,6 +306,18 @@ class ConfigFileTest(CoverageTest):
                     examples/
         """
 
+    # Just some sample tox.ini text from the docs.
+    TOX_INI = """\
+        [tox]
+        envlist = py{26,27,33,34,35}-{c,py}tracer
+        skip_missing_interpreters = True
+
+        [testenv]
+        commands =
+            # Create tests/zipmods.zip, install the egg1 egg
+            python igor.py zip_mods install_egg
+        """
+
     def assert_config_settings_are_correct(self, cov):
         """Check that `cov` has all the settings from LOTSA_SETTINGS."""
         self.assertTrue(cov.config.timid)
@@ -349,29 +363,44 @@ class ConfigFileTest(CoverageTest):
         cov = coverage.Coverage()
         self.assert_config_settings_are_correct(cov)
 
-    def test_config_file_settings_in_setupcfg(self):
+    def _test_config_file_settings_in_x(self, fname, contents):
         # Configuration will be read from setup.cfg from sections prefixed with
         # "coverage:"
         nested = self.LOTSA_SETTINGS.format(section="coverage:")
-        self.make_file("setup.cfg", nested + "\n" + self.SETUP_CFG)
+        fname = self.make_file(fname, nested + "\n" + contents)
         cov = coverage.Coverage()
         self.assert_config_settings_are_correct(cov)
 
-    def test_config_file_settings_in_setupcfg_if_coveragerc_specified(self):
-        # Configuration will be read from setup.cfg from sections prefixed with
-        # "coverage:", even if the API said to read from a (non-existent)
-        # .coveragerc file.
+    def test_config_file_settings_in_setupcfg(self):
+        self._test_config_file_settings_in_x("setup.cfg", self.SETUP_CFG)
+
+    def test_config_file_settings_in_toxini(self):
+        self._test_config_file_settings_in_x("tox.ini", self.TOX_INI)
+
+    def _test_config_file_settings_in_x_if_coveragerc_specified(self, fname,
+                                                                contents):
+        # Configuration will be read from a non-".coveragerc" file from
+        # sections prefixed with "coverage:", even if the API said to read from
+        # a (non-existent) .coveragerc file.
         nested = self.LOTSA_SETTINGS.format(section="coverage:")
-        self.make_file("setup.cfg", nested + "\n" + self.SETUP_CFG)
+        self.make_file(fname, nested + "\n" + contents)
         cov = coverage.Coverage(config_file=".coveragerc")
         self.assert_config_settings_are_correct(cov)
 
-    def test_setupcfg_only_if_not_coveragerc(self):
+    def test_config_file_settings_in_setupcfg_if_coveragerc_specified(self):
+        self._test_config_file_settings_in_x_if_coveragerc_specified(
+            "setup.cfg", self.SETUP_CFG)
+
+    def test_config_file_settings_in_tox_if_coveragerc_specified(self):
+        self._test_config_file_settings_in_x_if_coveragerc_specified(
+            "tox.ini", self.TOX_INI)
+
+    def _test_x_only_if_not_coveragerc(self, fname):
         self.make_file(".coveragerc", """\
             [run]
             include = foo
             """)
-        self.make_file("setup.cfg", """\
+        self.make_file(fname, """\
             [coverage:run]
             omit = bar
             branch = true
@@ -381,8 +410,14 @@ class ConfigFileTest(CoverageTest):
         self.assertEqual(cov.config.omit, None)
         self.assertEqual(cov.config.branch, False)
 
-    def test_setupcfg_only_if_prefixed(self):
-        self.make_file("setup.cfg", """\
+    def test_setupcfg_only_if_not_coveragerc(self):
+        self._test_x_only_if_not_coveragerc("setup.cfg")
+
+    def test_toxini_only_if_not_coveragerc(self):
+        self._test_x_only_if_not_coveragerc("tox.ini")
+
+    def _test_x_only_if_prefixed(self, fname):
+        self.make_file(fname, """\
             [run]
             omit = bar
             branch = true
@@ -391,6 +426,12 @@ class ConfigFileTest(CoverageTest):
         self.assertEqual(cov.config.omit, None)
         self.assertEqual(cov.config.branch, False)
 
+    def test_setupcfg_only_if_prefixed(self):
+        self._test_x_only_if_prefixed("setup.cfg")
+
+    def test_toxini_only_if_prefixed(self):
+        self._test_x_only_if_prefixed("tox.ini")
+
     def test_non_ascii(self):
         self.make_file(".coveragerc", """\
             [report]