Tie recursion calls to Dist object, not module

In change I1f2b4d34e587389f7e11b99d000e14477cf5091b, we attempted to
resolve an issue whereby using PBR as a PEP-517 backend could result in
recursion. We did this by setting 'dist.pbr' to 'None' but later
discovered this introduced a regression that prevented us from writing
the 'pbr.json' file into generated sdists. The fix for the regression,
change I407ae88ab8de4b61f94034b3d79a2ca7f7d79d16, stopped setting
'dist.pbr' to 'None' and instead set a global flag to indicate whether
we had already been called or not. Unfortunately it seems this fix is
also insufficent. As discussed in tox#2712 [1], tox v4 has implemented
its own implementation of PEP-517 - 'pyproject-api' [2] - and unlike
'build' this implementation optionally allows re-use of the backend
process for multiple PEP-517 commands. tox's 'Pep517VirtualEnvFrontend'
does just this. This means if we run multiple commands that require
generation of a 'Distribution' object - say,
'prepare_metadata_for_build_wheel' followed by 'build_sdist' - anything
but the first step will not result in proper population of said
'Distribution' objects.

The solution to this issue is simple: per $subject, instead of setting
our recursion-detection canary at the module level, set it at the
Distribution level.

[1] https://github.com/tox-dev/tox/issues/2712
[2] github.com/tox-dev/pyproject-api/

Change-Id: I67909d732a74550fbcd7c06a9e2f4ac88c063444
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

1 files changed, 2 insertions, 8 deletions

diff --git a/pbr/core.py b/pbr/core.py
index a801737..fb592f8 100644
--- a/pbr/core.py
+++ b/pbr/core.py
@@ -61,11 +61,6 @@ 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.
 
@@ -91,10 +86,9 @@ def pbr(dist, attr, value):
     # 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:
+    if hasattr(dist, '_pbr_initialized'):
         return
-    in_use = True
+    dist._pbr_initialized = True
 
     if not value:
         return