[PATCH 1 of 3 v2] profiling: allow nested usage of maybeprofile

[Arun Kulshreshtha]

# HG changeset patch
# User Arun Kulshreshtha <kulshrax at fb.com>
# Date 1474324901 25200
#      Mon Sep 19 15:41:41 2016 -0700
# Node ID 679c90104cc1fc92099ede6bd359f6ab5b10640d
# Parent  285a8c3e53f2183438f0cdbc238e4ab851d0d110
profiling: allow nested usage of maybeprofile

Add a check to the maybeprofile context manager to ensure that profiling
is only enabled once in nested invocations of this context manager.

Updated in v2 of this patch to reset itself once the root invocation
has exited. While not currently used, this ensures that maybeprofile
can be used in multiple (non-nested) places in a single run.

diff --git a/mercurial/profiling.py b/mercurial/profiling.py
--- a/mercurial/profiling.py
+++ b/mercurial/profiling.py
@@ -157,8 +157,15 @@
     just use a single code path for calling into code you may want to profile
     and this function determines whether to start profiling.
     """
-    if ui.configbool('profiling', 'enabled'):
+
+    # Guard against nested invocations of this context manager.
+    # Profiling should only be started in the outermost invocation.
+    alreadyenabled = getattr(maybeprofile, 'enabled', False)
+
+    if ui.configbool('profiling', 'enabled') and not alreadyenabled:
+        maybeprofile.enabled = True
         with profile(ui):
             yield
+        maybeprofile.enabled = False
     else:
         yield