phabstatus: fix interaction with the smartlog extension

Summary:
Previously phabstatus.extsetup() would throw an exception if the smartlog
extension was not in use and already loaded.

This fixes the code to use extensions.afterloaded() to ensure that we try to
wrap smartlog functions only after smartlog is loaded.  It also handles the
lookup error if smartlog is not in use at all.

Test Plan: Included a new unit test.

Reviewers: #mercurial, phillco

Reviewed By: phillco

Subscribers: medson, mjpieters, net-systems-diffs@fb.com

Differential Revision: https://phabricator.intern.facebook.com/D5375301

Tasks: 16939242

Signature: t1:5375301:1499323251:4bc00c9cba79d60cbbb6738e8f1d648e75055cdb

hgext3rd/phabstatus.py

@@ -193,5 +193,13 @@ def _getdag(orig, *args):
     return orig(*args)
 
 def extsetup(ui):
-    smartlog = extensions.find("smartlog")
+    def _smartlogloaded(loaded):
+        smartlog = None
+        try:
+            smartlog = extensions.find('smartlog')
+        except KeyError:
+            pass
+        if smartlog:
             extensions.wrapfunction(smartlog, 'getdag', _getdag)
+
+    extensions.afterloaded('smartlog', _smartlogloaded)

tests/test-phabstatus.t

@@ -59,6 +59,15 @@ And finally, the success case
   $ HG_ARC_CONDUIT_MOCK=$TESTTMP/mockduit hg log -T '{phabstatus}\n' -r .
   Needs Review
 
+Make sure the code works without the smartlog extensions
+
+  $ cat > $TESTTMP/mockduit << EOF
+  > [{"cmd": ["differential.querydiffhashes", {"revisionIDs": ["1"]}],
+  >   "result": {"1" : {"count": 1, "status": "Needs Review", "hash": "lolwut"}}}]
+  > EOF
+  $ HG_ARC_CONDUIT_MOCK=$TESTTMP/mockduit hg --config 'extensions.smartlog=!' log -T '{phabstatus}\n' -r .
+  Needs Review
+
 Make sure the template keywords are documented correctly
 
   $ hg help templates | egrep 'phabstatus|syncstatus'