[PATCH] extensions: add loadfailed to return extensions failed to load (API)

[Jun Wu]

# HG changeset patch
# User Jun Wu <quark at fb.com>
# Date 1455123574 0
#      Wed Feb 10 16:59:34 2016 +0000
# Node ID d58f659625ed84ce90f6eef1403199ba4f18f037
# Parent  a036e1ae1fbe88ab99cb861ebfc2e4da7a3912ca
extensions: add loadfailed to return extensions failed to load (API)

chgserver is designed to preload all the extensions specified in config. The
server needs to know which extensions fail to load to take futher action, for
example, reload these extensions or refuse to continue. There is no easy way
to know this kind of information without duplicating part of extensions.py.

This patch adds extensions.loadfailed() to access names of extensions failed
to load.

diff --git a/mercurial/extensions.py b/mercurial/extensions.py
--- a/mercurial/extensions.py
+++ b/mercurial/extensions.py
@@ -26,6 +26,7 @@
 _order = []
 _builtin = set(['hbisect', 'bookmarks', 'parentrevspec', 'progress', 'interhg',
                 'inotify'])
+_loadfailed = set()
 
 def extensions(ui=None):
     if ui:
@@ -130,6 +131,7 @@
         except KeyboardInterrupt:
             raise
         except Exception as inst:
+            _loadfailed.add(name)
             if path:
                 ui.warn(_("*** failed to import extension %s from %s: %s\n")
                         % (name, path, inst))
@@ -456,6 +458,9 @@
 
     return exts
 
+def loadfailed():
+    return list(_loadfailed)
+
 def moduleversion(module):
     '''return version information from given module as a string'''
     if (util.safehasattr(module, 'getversion')
diff --git a/tests/test-bad-extension.t b/tests/test-bad-extension.t
--- a/tests/test-bad-extension.t
+++ b/tests/test-bad-extension.t
@@ -38,3 +38,16 @@
   *** failed to import extension badext2: No module named badext2
   Traceback (most recent call last):
   ImportError: No module named badext2
+
+names of extensions failed to load can be accessed via extensions.loadfailed()
+
+  $ cat <<EOF > printproblemic.py
+  > from mercurial import cmdutil, commands, extensions
+  > cmdtable = {}
+  > command = cmdutil.command(cmdtable)
+  > @command('badexts', norepo=True)
+  > def badexts(*args):
+  >     print('BADEXTS: %s' % ' '.join(sorted(extensions.loadfailed())))
+  > EOF
+  $ hg --config extensions.a=printproblemic.py badexts 2>&1 | grep ^BADEXTS
+  BADEXTS: badext badext2