extensions: catch uisetup and extsetup failures and don't let them break hg

extensions: catch uisetup and extsetup failures and don't let them break hg

Otherwise users of the patience diff extension will be unable to run
anything at all in hg 4.3 until they figure out what's broken.

--- a/mercurial/extensions.py	Tue Jun 06 10:03:16 2017 -0400
+++ b/mercurial/extensions.py	Tue Jun 06 10:09:48 2017 -0400
@@ -167,17 +167,31 @@
 def _runuisetup(name, ui):
     uisetup = getattr(_extensions[name], 'uisetup', None)
     if uisetup:
-        uisetup(ui)
+        try:
+            uisetup(ui)
+        except Exception as inst:
+            ui.traceback()
+            msg = _forbytes(inst)
+            ui.warn(_("*** failed to set up extension %s: %s\n") % (name, msg))
+            return False
+    return True
 
 def _runextsetup(name, ui):
     extsetup = getattr(_extensions[name], 'extsetup', None)
     if extsetup:
         try:
-            extsetup(ui)
-        except TypeError:
-            if inspect.getargspec(extsetup).args:
-                raise
-            extsetup() # old extsetup with no ui argument
+            try:
+                extsetup(ui)
+            except TypeError:
+                if inspect.getargspec(extsetup).args:
+                    raise
+                extsetup() # old extsetup with no ui argument
+        except Exception as inst:
+            ui.traceback()
+            msg = _forbytes(inst)
+            ui.warn(_("*** failed to set up extension %s: %s\n") % (name, msg))
+            return False
+    return True
 
 def loadall(ui, whitelist=None):
     result = ui.configitems("extensions")
@@ -203,11 +217,19 @@
                 ui.warn(_("*** (%s)\n") % inst.hint)
             ui.traceback()
 
+    broken = set()
     for name in _order[newindex:]:
-        _runuisetup(name, ui)
+        if not _runuisetup(name, ui):
+            broken.add(name)
 
     for name in _order[newindex:]:
-        _runextsetup(name, ui)
+        if name in broken:
+            continue
+        if not _runextsetup(name, ui):
+            broken.add(name)
+
+    for name in broken:
+        _extensions[name] = None
 
     # Call aftercallbacks that were never met.
     for shortname in _aftercallbacks:

--- a/tests/test-extension.t	Tue Jun 06 10:03:16 2017 -0400
+++ b/tests/test-extension.t	Tue Jun 06 10:09:48 2017 -0400
@@ -1625,9 +1625,35 @@
   > baduisetup = $PWD/baduisetup.py
   > EOF
 
-Broken: an extension that triggers the import of bdiff during uisetup
-can't be easily debugged:
+Even though the extension fails during uisetup, hg is still basically usable:
   $ hg version
-  abort: No module named bdiff!
-  (did you forget to compile extensions?)
-  [255]
+  *** failed to set up extension baduisetup: No module named bdiff
+  Mercurial Distributed SCM (version *) (glob)
+  (see https://mercurial-scm.org for more information)
+  
+  Copyright (C) 2005-2017 Matt Mackall and others
+  This is free software; see the source for copying conditions. There is NO
+  warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+
+  $ hg version --traceback
+  Traceback (most recent call last):
+    File "*/mercurial/extensions.py", line *, in _runuisetup (glob)
+      uisetup(ui)
+    File "$TESTTMP/baduisetup.py", line 10, in uisetup
+      extensions.wrapfunction(bdiff, 'blocks', blockswrapper)
+    File "*/mercurial/extensions.py", line *, in wrapfunction (glob)
+      origfn = getattr(container, funcname)
+    File "*/hgdemandimport/demandimportpy2.py", line *, in __getattr__ (glob)
+      self._load()
+    File "*/hgdemandimport/demandimportpy2.py", line *, in _load (glob)
+      mod = _hgextimport(_import, head, globals, locals, None, level)
+    File "*/hgdemandimport/demandimportpy2.py", line *, in _hgextimport (glob)
+      return importfunc(name, globals, *args, **kwargs)
+  ImportError: No module named bdiff
+  *** failed to set up extension baduisetup: No module named bdiff
+  Mercurial Distributed SCM (version *) (glob)
+  (see https://mercurial-scm.org for more information)
+  
+  Copyright (C) 2005-2017 Matt Mackall and others
+  This is free software; see the source for copying conditions. There is NO
+  warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

--- a/tests/test-flagprocessor.t	Tue Jun 06 10:03:16 2017 -0400
+++ b/tests/test-flagprocessor.t	Tue Jun 06 10:09:48 2017 -0400
@@ -161,7 +161,8 @@
   > EOF
   $ echo 'this should fail' > file
   $ hg commit -Aqm 'add file'
-  abort: cannot register multiple processors on flag '0x8'.
+  *** failed to set up extension duplicate: cannot register multiple processors on flag '0x8'.
+  abort: missing processor for flag '0x1'!
   [255]
 
   $ cd ..