From bfda2a0050943f0ead1fec3b18a52d32c07f34fa Mon Sep 17 00:00:00 2001
From: Daniel Hahler <git@thequod.de>
Date: Thu, 28 Mar 2019 00:27:23 +0100
Subject: [PATCH] setup.cfg: use existing [tool:pytest] (ignoring [pytest])

---
 changelog/5008.feature.rst      |  3 +++
 src/_pytest/config/findpaths.py | 12 ++++++------
 testing/test_config.py          | 16 ++++++++++++++++
 3 files changed, 25 insertions(+), 6 deletions(-)
 create mode 100644 changelog/5008.feature.rst

diff --git a/changelog/5008.feature.rst b/changelog/5008.feature.rst
new file mode 100644
index 000000000..17d2770fe
--- /dev/null
+++ b/changelog/5008.feature.rst
@@ -0,0 +1,3 @@
+If a ``setup.cfg`` file contains ``[tool:pytest]`` and also the no longer supported ``[pytest]`` section, pytest will use ``[tool:pytest]`` ignoring ``[pytest]``. Previously it would unconditionally error out.
+
+This makes it simpler for plugins to support old pytest versions.
diff --git a/src/_pytest/config/findpaths.py b/src/_pytest/config/findpaths.py
index a0f16134d..fa2024470 100644
--- a/src/_pytest/config/findpaths.py
+++ b/src/_pytest/config/findpaths.py
@@ -33,7 +33,12 @@ def getcfg(args, config=None):
                 p = base.join(inibasename)
                 if exists(p):
                     iniconfig = py.iniconfig.IniConfig(p)
-                    if "pytest" in iniconfig.sections:
+                    if (
+                        inibasename == "setup.cfg"
+                        and "tool:pytest" in iniconfig.sections
+                    ):
+                        return base, p, iniconfig["tool:pytest"]
+                    elif "pytest" in iniconfig.sections:
                         if inibasename == "setup.cfg" and config is not None:
 
                             fail(
@@ -41,11 +46,6 @@ def getcfg(args, config=None):
                                 pytrace=False,
                             )
                         return base, p, iniconfig["pytest"]
-                    if (
-                        inibasename == "setup.cfg"
-                        and "tool:pytest" in iniconfig.sections
-                    ):
-                        return base, p, iniconfig["tool:pytest"]
                     elif inibasename == "pytest.ini":
                         # allowed to be empty
                         return base, p, {}
diff --git a/testing/test_config.py b/testing/test_config.py
index 07654e5ad..28cc3ab91 100644
--- a/testing/test_config.py
+++ b/testing/test_config.py
@@ -46,6 +46,22 @@ class TestParseIni(object):
         """correctly handle zero length arguments (a la pytest '')"""
         getcfg([""])
 
+    def test_setupcfg_uses_toolpytest_with_pytest(self, testdir):
+        p1 = testdir.makepyfile("def test(): pass")
+        testdir.makefile(
+            ".cfg",
+            setup="""
+                [tool:pytest]
+                testpaths=%s
+                [pytest]
+                testpaths=ignored
+        """
+            % p1.basename,
+        )
+        result = testdir.runpytest()
+        result.stdout.fnmatch_lines(["*, inifile: setup.cfg, *", "* 1 passed in *"])
+        assert result.ret == 0
+
     def test_append_parse_args(self, testdir, tmpdir, monkeypatch):
         monkeypatch.setenv("PYTEST_ADDOPTS", '--color no -rs --tb="short"')
         tmpdir.join("pytest.ini").write(