Avoid recursive calls into SetupTools entrypoint

Add a check in pbr.core.pbr() to make sure it hasn't already run,
and return immediately if it has. This replaces the earlier attempt
at loop-busting by setting the entrypoint to None in the dist, in
order to support PEP 517 builds without setup_requires.

Also test that pbr.json is now included in the dist tree, in order
to avoid future regressions.

Change-Id: I407ae88ab8de4b61f94034b3d79a2ca7f7d79d16

pbr/core.py

@@ -61,6 +61,11 @@ else:
     integer_types = (int, long)  # noqa
 
 
+# We use this canary to detect whether the module has already been called,
+# in order to avoid recursion
+in_use = False
+
+
 def pbr(dist, attr, value):
     """Implements the actual pbr setup() keyword.
 
@@ -81,6 +86,16 @@ def pbr(dist, attr, value):
     not work well with distributions that do use a `Distribution` subclass.
     """
 
+    # Distribution.finalize_options() is what calls this method. That means
+    # there is potential for recursion here. Recursion seems to be an issue
+    # particularly when using PEP517 build-system configs without
+    # setup_requires in setup.py. We can avoid the recursion by setting
+    # this canary so we don't repeat ourselves.
+    global in_use
+    if in_use:
+        return
+    in_use = True
+
     if not value:
         return
     if isinstance(value, string_type):
@@ -130,14 +145,6 @@ def pbr(dist, attr, value):
                 msg = 'Unknown distribution option: %s' % repr(key)
                 warnings.warn(msg)
 
-    # Distribution.finalize_options() is what calls this method. That means
-    # there is potential for recursion here. Recursion seems to be an issue
-    # particularly when using PEP517 build-system configs without
-    # setup_requires in setup.py. We can avoid the recursion by setting
-    # dist.pbr to a None value as the corresponding entrypoint (this function)
-    # will only be called on a non None value.
-    setattr(dist, "pbr", None)
-
     # Re-finalize the underlying Distribution
     try:
         super(dist.__class__, dist).finalize_options()

pbr/tests/test_packaging.py

@@ -381,6 +381,12 @@ class TestPackagingWheels(base.BaseTestCase):
         wheel_file.extractall(self.extracted_wheel_dir)
         wheel_file.close()
 
+    def test_metadata_directory_has_pbr_json(self):
+        # Build the path to the scripts directory
+        pbr_json = os.path.join(
+            self.extracted_wheel_dir, 'pbr_testpackage-0.0.dist-info/pbr.json')
+        self.assertTrue(os.path.exists(pbr_json))
+
     def test_data_directory_has_wsgi_scripts(self):
         # Build the path to the scripts directory
         scripts_dir = os.path.join(