Added Bug.extra_strings to support add-on functionality, e.g. `be tag`.

Versioned properties whose data is a mutable type are tricky, since
the simple comparisons we'd been using in
libbe.properties.change_hook_property don't work for mutables.  For
now, we avoid that problem by assuming a change happened whenever a
mutable property is set.  change_hook_property is a bit untidy at the
moment while I work out how to deal with mutables.

As an example of using Bug.extra_strings to patch on some useful
functionality, I've written becommands/tag.py.  I'd suggest future
add-ons (e.g. becommands/depend.py?) use the "<LABEL>:<value>" string
format to keep it easy to sort out which strings belong to which
add-ons.  tag.py is still missing command line tag-removal and
tag-searching for `be list'.  Perhaps something like

  be list --extra-strings TAG:<your-tag>,TAG:<another-tag>,DEPEND:<bug-id> 

would be good, although it would requre escaping commas from the tags,
or refusing to allow commas in the tags...

libbe.properties.ValueCheckError also got a minor update so the
printed error message makes sense when raised with allowed being an
iterable (i.e. check_property) or a function
(e.g. fn_checked_property).

All of this digging around turned up a really buggy
libbe.bugdir.MultipleBugMatches.  Obviously I had never actually
called it before :p.  Should be fixed now.

libbe.comment._set_comment_body has also been normalized to match the
suggested change_hook interface: change_hook(self, old, new).
Although, I'm not sure why it hadn't been causing obvious problems
before, so maybe I'm misunderstanding something about that.

1 files changed, 20 insertions, 0 deletions

diff --git a/libbe/bug.py b/libbe/bug.py
index 43974dd..89c0266 100644
--- a/libbe/bug.py
+++ b/libbe/bug.py
@@ -18,6 +18,7 @@ import os
 import os.path
 import errno
 import time
+import types
 import xml.sax.saxutils
 import doctest
 
@@ -184,6 +185,25 @@ class Bug(settings_object.SavedSettingsObject):
                     fset=_set_time,
                     doc="An integer version of .time_string")
 
+    def _extra_strings_check_fn(value):
+        "Require an iterable full of strings"
+        if not hasattr(value, "__iter__"):
+            return False
+        for x in value:
+            if type(x) not in types.StringTypes:
+                return False
+        return True
+    def _extra_strings_change_hook(self, old, new):
+        self.extra_strings.sort() # to make merging easier
+        self._prop_save_settings(old, new)
+    @_versioned_property(name="extra_strings",
+                         doc="Space for an array of extra strings.  Useful for storing state for functionality implemented purely in becommands/<some_function>.py.",
+                         default=[],
+                         check_fn=_extra_strings_check_fn,
+                         change_hook=_extra_strings_change_hook,
+                         mutable=True)
+    def extra_strings(): return {}
+
     @_versioned_property(name="summary",
                          doc="A one-line bug description")
     def summary(): return {}