[PATCH 2 of 2 RFC] dispatch: try and identify third-party extensions as sources of tracebacks

[Augie Fackler]

# HG changeset patch
# User Augie Fackler <durin42 at gmail.com>
# Date 1311622871 18000
# Node ID 245f5bbe00788d00ed4e6d6bd27a22c5163365f1
# Parent  e59468fa239985828ce199d3ae8cb1768987525c
dispatch: try and identify third-party extensions as sources of tracebacks

Extension authors should explicitly declare their supported hg
versions and include a buglink attribute in their extension.

Packagers should make every effort to ship hg versions from exact
tags, or with as few modifications as possible so that the versioning
can work appropriately.

diff --git a/mercurial/dispatch.py b/mercurial/dispatch.py
--- a/mercurial/dispatch.py
+++ b/mercurial/dispatch.py
@@ -201,14 +201,34 @@
     except socket.error, inst:
         ui.warn(_("abort: %s\n") % inst.args[-1])
     except:
-        ui.warn(_("** unknown exception encountered,"
-                  " please report by visiting\n"))
-        ui.warn(_("**  http://mercurial.selenic.com/wiki/BugTracker\n"))
-        ui.warn(_("** Python %s\n") % sys.version.replace('\n', ''))
-        ui.warn(_("** Mercurial Distributed SCM (version %s)\n")
-               % util.version())
-        ui.warn(_("** Extensions loaded: %s\n")
-               % ", ".join([x[0] for x in extensions.extensions()]))
+        myver = util.version()
+        # For compatibility checking, we discard the portion of the hg
+        # version after the + on the assumption that if a "normal
+        # user" is running a build with a + in it the packager
+        # probably built from fairly close to a tag and anyone with a
+        # 'make local' copy of hg (where the version number can be out
+        # of date) will be clueful enough to notice the implausible
+        # version number and try updating.
+        compare = myver.split('+')[0]
+        for name, mod in extensions.extensions():
+            hgversions = getattr(mod, 'hgversions', [])
+            if compare not in hgversions and 'internal' not in hgversions:
+                report = getattr(mod, 'buglink', _('the extension author.'))
+                warning = (_('** Unknown exception encountered with '
+                             'possibly-broken third-party extension %s.\n'
+                             '** Please disable %s and try your action again.\n'
+                             '** If that fixes the bug please report it to %s\n')
+                           % (name, name, report))
+                break
+        else:
+            warning = (_("** unknown exception encountered, "
+                         "please report by visiting\n") +
+                       _("** http://mercurial.selenic.com/wiki/BugTracker\n"))
+        warning += ((_("** Python %s\n") % sys.version.replace('\n', '')) +
+                    (_("** Mercurial Distributed SCM (version %s)\n") % myver) +
+                    (_("** Extensions loaded: %s\n") %
+                     ", ".join([x[0] for x in extensions.extensions()])))
+        ui.warn(warning)
         raise
 
     return -1
diff --git a/tests/test-extension.t b/tests/test-extension.t
--- a/tests/test-extension.t
+++ b/tests/test-extension.t
@@ -475,3 +475,44 @@
   hg: unknown command 'foo'
   warning: error finding commands in $TESTTMP/hgext/forest.py
   [255]
+
+  $ cat > throw.py <<EOF
+  > from mercurial import cmdutil, commands
+  > cmdtable = {}
+  > command = cmdutil.command(cmdtable)
+  > class Bogon(Exception): pass
+  > 
+  > @command('throw', [], 'hg throw')
+  > def throw(ui, **opts):
+  >     """throws an exception"""
+  >     raise Bogon()
+  > commands.norepo += " throw"
+  > EOF
+No declared supported version, extension complains:
+  $ hg --config extensions.throw=throw.py throw 2>&1 | egrep '^\*\*'
+  ** Unknown exception encountered with possibly-broken third-party extension throw.
+  ** Please disable throw and try your action again.
+  ** If that fixes the bug please report it to the extension author.
+  ** Python * (glob)
+  ** Mercurial Distributed SCM * (glob)
+  ** Extensions loaded: throw
+If the extension specifies a buglink, show that:
+  $ echo 'buglink = "http://example.com/bts"' >> throw.py
+  $ rm -f throw.pyc throw.pyo
+  $ hg --config extensions.throw=throw.py throw 2>&1 | egrep '^\*\*'
+  ** Unknown exception encountered with possibly-broken third-party extension throw.
+  ** Please disable throw and try your action again.
+  ** If that fixes the bug please report it to http://example.com/bts
+  ** Python * (glob)
+  ** Mercurial Distributed SCM (*) (glob)
+  ** Extensions loaded: throw
+Declare the version as supporting this hg version, show regular bts link:
+  $ hgver=$(python -c 'from mercurial import util; print util.version().split("+")[0]')
+  $ echo 'hgversions = ["""'"$hgver"'"""]' >> throw.py
+  $ rm -f throw.pyc throw.pyo
+  $ hg --config extensions.throw=throw.py throw 2>&1 | egrep '^\*\*'
+  ** unknown exception encountered, please report by visiting
+  ** http://mercurial.selenic.com/wiki/BugTracker
+  ** Python * (glob)
+  ** Mercurial Distributed SCM (*) (glob)
+  ** Extensions loaded: throw