Fix global configuration fallback in Jenkins runs (#1466)

Fixes #1428

When running in Jenkins and using `setup.cfg`, tox would not fall back
to the [tox:tox] configuration properly. This was due to how the
fallback section name was calculated in this specific combination of
characteristics.

on-behalf-of: @ithaka <dane.hillard@ithaka.org>

CONTRIBUTORS

@@ -19,6 +19,7 @@ Chris Jerdonek
 Chris Rose
 Clark Boylan
 Cyril Roelandt
+Dane Hillard
 David Staheli
 Ederag
 Eli Collins

docs/changelog/1428.bugfix.rst

@@ -0,0 +1 @@
+Fix fallback to global configuration when running in Jenkins. - by :user:`daneah`

src/tox/_pytestplugin.py

@@ -102,12 +102,12 @@ def check_os_environ_stable():
 
 @pytest.fixture(name="newconfig")
 def create_new_config_file(tmpdir):
-    def create_new_config_file_(args, source=None, plugins=()):
+    def create_new_config_file_(args, source=None, plugins=(), filename="tox.ini"):
         if source is None:
             source = args
             args = []
         s = textwrap.dedent(source)
-        p = tmpdir.join("tox.ini")
+        p = tmpdir.join(filename)
         p.write(s)
         tox.session.setup_reporter(args)
         with tmpdir.as_cwd():

src/tox/config/__init__.py

@@ -991,11 +991,12 @@ def line_of_default_to_zero(section, name=None):
         self.config = config
 
         prefix = "tox" if ini_path.basename == "setup.cfg" else None
+        fallbacksection = "tox:tox" if ini_path.basename == "setup.cfg" else "tox"
 
         context_name = getcontextname()
         if context_name == "jenkins":
             reader = SectionReader(
-                "tox:jenkins", self._cfg, prefix=prefix, fallbacksections=["tox"]
+                "tox:jenkins", self._cfg, prefix=prefix, fallbacksections=[fallbacksection]
             )
             dist_share_default = "{toxworkdir}/distshare"
         elif not context_name:

tests/unit/config/test_config.py

@@ -2104,6 +2104,17 @@ def test_quiet(self, args, expected, newconfig):
         config = newconfig(args, "")
         assert config.option.quiet_level == expected
 
+    def test_substitution_jenkins_global(self, monkeypatch, newconfig):
+        monkeypatch.setenv("HUDSON_URL", "xyz")
+        config = newconfig(
+            """
+            [tox:tox]
+            envlist = py37
+        """,
+            filename="setup.cfg",
+        )
+        assert "py37" in config.envconfigs
+
     def test_substitution_jenkins_default(self, monkeypatch, newconfig):
         monkeypatch.setenv("HUDSON_URL", "xyz")
         config = newconfig(