From 0ae27714d1940cb012827faf56245c23cb40d113 Mon Sep 17 00:00:00 2001
From: Dirk Thomas <dirk-thomas@users.noreply.github.com>
Date: Tue, 4 Jun 2019 10:41:58 -0700
Subject: [PATCH] Backport of #5389: fix for 'files' = None in broken metadata

---
 changelog/5389.bugfix.rst      |  1 +
 src/_pytest/config/__init__.py |  2 +-
 testing/test_config.py         | 23 +++++++++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 changelog/5389.bugfix.rst

diff --git a/changelog/5389.bugfix.rst b/changelog/5389.bugfix.rst
new file mode 100644
index 00000000000..debf0a9da9d
--- /dev/null
+++ b/changelog/5389.bugfix.rst
@@ -0,0 +1 @@
+Fix regressions of `#5063 <https://github.com/pytest-dev/pytest/pull/5063>`__ for ``importlib_metadata.PathDistribution`` which have their ``files`` attribute being ``None``.
diff --git a/src/_pytest/config/__init__.py b/src/_pytest/config/__init__.py
index 7a5deb13f53..6d44bf3d773 100644
--- a/src/_pytest/config/__init__.py
+++ b/src/_pytest/config/__init__.py
@@ -800,7 +800,7 @@ def _mark_plugins_for_rewrite(self, hook):
             str(file)
             for dist in importlib_metadata.distributions()
             if any(ep.group == "pytest11" for ep in dist.entry_points)
-            for file in dist.files
+            for file in dist.files or []
         )
 
         for name in _iter_rewritable_modules(package_files):
diff --git a/testing/test_config.py b/testing/test_config.py
index e588c262a9c..eefd908de59 100644
--- a/testing/test_config.py
+++ b/testing/test_config.py
@@ -586,6 +586,29 @@ def distributions():
         testdir.parseconfig()
 
 
+def test_importlib_metadata_broken_distribution(testdir, monkeypatch):
+    """Integration test for broken distributions with 'files' metadata being None (#5389)"""
+    monkeypatch.delenv("PYTEST_DISABLE_PLUGIN_AUTOLOAD", raising=False)
+
+    class DummyEntryPoint:
+        name = "mytestplugin"
+        group = "pytest11"
+
+        def load(self):
+            return object()
+
+    class Distribution:
+        version = "1.0"
+        files = None
+        entry_points = (DummyEntryPoint(),)
+
+    def distributions():
+        return (Distribution(),)
+
+    monkeypatch.setattr(importlib_metadata, "distributions", distributions)
+    testdir.parseconfig()
+
+
 @pytest.mark.parametrize("block_it", [True, False])
 def test_plugin_preparse_prevents_setuptools_loading(testdir, monkeypatch, block_it):
     monkeypatch.delenv("PYTEST_DISABLE_PLUGIN_AUTOLOAD", raising=False)