Allow PEP517 without setup_requires

When using PBR PEP517 support without setup_requires were were
infinitely recursing because Distribution.finalize_options calls pbr()
and pbr() calls Distribution.finalize_options. With a setup_requires
this doesn't seem to happen because something is resetting dist.pbr's
value from True (callable) to None (not callable) after the initial
pbr() call and before further recursion can occur.

Explicitly enforce this behavior in pbr() via an explicit update of
dist.pbr to None to avoid calling pbr() more than once resulting in the
unwanted loop.

Change-Id: I1f2b4d34e587389f7e11b99d000e14477cf5091b

2 files changed, 14 insertions, 1 deletions

diff --git a/pbr/core.py b/pbr/core.py
index 645a2ef..f221299 100644
--- a/pbr/core.py
+++ b/pbr/core.py
@@ -130,6 +130,14 @@ 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()
diff --git a/pbr/tests/test_packaging.py b/pbr/tests/test_packaging.py
index a024f56..7735053 100644
--- a/pbr/tests/test_packaging.py
+++ b/pbr/tests/test_packaging.py
@@ -930,7 +930,12 @@ class TestPEP517Support(base.BaseTestCase):
                         sphinx
                         iso8601
                     """),
-                    # Use default PBR test setup.py.
+                    # Override default setup.py to remove setup_requires.
+                    'setup.py': textwrap.dedent("""\
+                        #!/usr/bin/env python
+                        import setuptools
+                        setuptools.setup(pbr=True)
+                    """),
                     'setup.cfg': textwrap.dedent("""\
                         [metadata]
                         name = test_pep517