# HG changeset patch
# User Yuya Nishihara <yuya@tcha.org>
# Date 1427700215 -32400
# Node ID de23a552fc23e241b4c510200bc913012c123708
# Parent  3ff4b07412ad709d57e304c139d05469fede8fce
extensions: show traceback on load failure if --traceback flag is set

Before this patch, there was no handy way to investigate the reason why
extension couldn't be loaded.

If ui.debug is set, tracebacks of both "hgext.foo" and "foo" are displayed
because the first ImportError could occur at very deep dependency module.

diff -r 3ff4b07412ad -r de23a552fc23 mercurial/extensions.py
--- a/mercurial/extensions.py	Sun May 31 14:40:28 2015 +0900
+++ b/mercurial/extensions.py	Mon Mar 30 16:23:35 2015 +0900
@@ -85,6 +85,8 @@
         except ImportError, err:
             ui.debug('could not import hgext.%s (%s): trying %s\n'
                      % (name, err, name))
+            if ui.debugflag:
+                ui.traceback()
             mod = importh(name)
     _extensions[shortname] = mod
     _order.append(shortname)
@@ -110,6 +112,7 @@
             else:
                 ui.warn(_("*** failed to import extension %s: %s\n")
                         % (name, inst))
+            ui.traceback()
 
     for name in _order[newindex:]:
         uisetup = getattr(_extensions[name], 'uisetup', None)
diff -r 3ff4b07412ad -r de23a552fc23 tests/test-bad-extension.t
--- a/tests/test-bad-extension.t	Sun May 31 14:40:28 2015 +0900
+++ b/tests/test-bad-extension.t	Mon Mar 30 16:23:35 2015 +0900
@@ -15,3 +15,32 @@
   hg help [-ec] [TOPIC]
   
   show help for a given topic or a help overview
+
+show traceback
+
+  $ hg -q help help --traceback 2>&1 | grep -v '^  '
+  *** failed to import extension badext from $TESTTMP/badext.py: bit bucket overflow
+  Traceback (most recent call last):
+  Exception: bit bucket overflow
+  *** failed to import extension badext2: No module named badext2
+  Traceback (most recent call last):
+  ImportError: No module named badext2
+  hg help [-ec] [TOPIC]
+  
+  show help for a given topic or a help overview
+
+show traceback for ImportError of hgext.name if debug is set
+(note that --debug option isn't applied yet when loading extensions)
+
+  $ hg help help --traceback --config ui.debug=True 2>&1 \
+  > | grep -v '^  ' | head -n10
+  *** failed to import extension badext from $TESTTMP/badext.py: bit bucket overflow
+  Traceback (most recent call last):
+  Exception: bit bucket overflow
+  could not import hgext.badext2 (No module named badext2): trying badext2
+  Traceback (most recent call last):
+  ImportError: No module named badext2
+  *** failed to import extension badext2: No module named badext2
+  Traceback (most recent call last):
+  ImportError: No module named badext2
+  hg help [-ec] [TOPIC]