From 9500b2459f4d8eb5485c04596f5a59d46f0fa27b Mon Sep 17 00:00:00 2001 From: Richard van der Hoff Date: Mon, 30 Mar 2020 18:31:45 +0100 Subject: [PATCH] Fix a bug which could cause incorrect 'cyclic dependency' error. If there was an exception setting up one of the attributes of the Homeserver god object, then future attempts to fetch that attribute would raise a confusing "Cyclic dependency" error. Let's make sure that we clear the `building` flag so that we just get the original exception. Ref: #7169 --- changelog.d/7178.bugfix | 1 + synapse/server.py | 22 ++++++++++------------ 2 files changed, 11 insertions(+), 12 deletions(-) create mode 100644 changelog.d/7178.bugfix diff --git a/changelog.d/7178.bugfix b/changelog.d/7178.bugfix new file mode 100644 index 000000000000..35ea645d7596 --- /dev/null +++ b/changelog.d/7178.bugfix @@ -0,0 +1 @@ +Fix a bug which could cause incorrect 'cyclic dependency' error. diff --git a/synapse/server.py b/synapse/server.py index cd86475d6bb0..9228e1c8927c 100644 --- a/synapse/server.py +++ b/synapse/server.py @@ -583,24 +583,22 @@ def _get(hs): try: builder = getattr(hs, "build_%s" % (depname)) except AttributeError: - builder = None + raise NotImplementedError( + "%s has no %s nor a builder for it" % (type(hs).__name__, depname) + ) - if builder: - # Prevent cyclic dependencies from deadlocking - if depname in hs._building: - raise ValueError("Cyclic dependency while building %s" % (depname,)) - hs._building[depname] = 1 + # Prevent cyclic dependencies from deadlocking + if depname in hs._building: + raise ValueError("Cyclic dependency while building %s" % (depname,)) + hs._building[depname] = 1 + try: dep = builder() setattr(hs, depname, dep) - + finally: del hs._building[depname] - return dep - - raise NotImplementedError( - "%s has no %s nor a builder for it" % (type(hs).__name__, depname) - ) + return dep setattr(HomeServer, "get_%s" % (depname), _get)