Merge lp:~vila/bzr/832064-default-value-callable into lp:bzr

[Vincent Ladeuil]

Allow callables to be used to specify config option default values

Easy fix for a medium bug allowing more options to be migrated trivially.

When registering an option, it is now possible to specify a python callable
which must return a unicode string (from_unicode will be called if/when
needed).

[Jelmer Vernooij (jelmer)]

review: Approve

[Vincent Ladeuil (vila)]

sent to pqm by email

=== modified file 'bzrlib/config.py'
--- bzrlib/config.py	2011-12-09 12:04:25 +0000
+++ bzrlib/config.py	2011-12-09 16:30:32 +0000
@@ -2331,8 +2331,10 @@
 
         :param default: the default value to use when none exist in the config
             stores. This is either a string that ``from_unicode`` will convert
-            into the proper type or a python object that can be stringified (so
-            only the empty list is supported for example).
+            into the proper type, a callable returning a unicode string so that
+            ``from_unicode`` can be used on the return value, or a python
+            object that can be stringified (so only the empty list is supported
+            for example).
 
         :param default_from_env: A list of environment variables which can
            provide a default value. 'default' will be used only if none of the
@@ -2367,6 +2369,8 @@
         elif isinstance(default, (str, unicode, bool, int, float)):
             # Rely on python to convert strings, booleans and integers
             self.default = u'%s' % (default,)
+        elif callable(default):
+            self.default = default
         else:
             # other python objects are not expected
             raise AssertionError('%r is not supported as a default value'
@@ -2407,7 +2411,13 @@
                 continue
         if value is None:
             # Otherwise, fallback to the value defined at registration
-            value = self.default
+            if callable(self.default):
+                value = self.default()
+                if not isinstance(value, unicode):
+                    raise AssertionError(
+                    'Callable default values should be unicode')
+            else:
+                value = self.default
         return value
 
     def get_help_text(self, additional_see_also=None, plain=True):
 
=== modified file 'bzrlib/tests/test_config.py'
--- bzrlib/tests/test_config.py	2011-12-09 12:04:25 +0000
+++ bzrlib/tests/test_config.py	2011-12-09 16:30:32 +0000
@@ -2275,6 +2275,12 @@
         opt = config.Option('foo', default='bar')
         self.assertEquals('bar', opt.get_default())
 
+    def test_callable_default_value(self):
+        def bar_as_unicode():
+            return u'bar'
+        opt = config.Option('foo', default=bar_as_unicode)
+        self.assertEquals('bar', opt.get_default())
+
     def test_default_value_from_env(self):
         opt = config.Option('foo', default='bar', default_from_env=['FOO'])
         self.overrideEnv('FOO', 'quux')
@@ -2296,6 +2302,12 @@
         self.assertRaises(AssertionError, config.Option, 'foo',
                           default=object())
 
+    def test_not_supported_callable_default_value_not_unicode(self):
+        def bar_not_unicode():
+            return 'bar'
+        opt = config.Option('foo', default=bar_not_unicode)
+        self.assertRaises(AssertionError, opt.get_default)
+
 
 class TestOptionConverterMixin(object):
 
@@ -2363,6 +2375,7 @@
         opt = self.get_option()
         self.assertConverted(16, opt, u'16')
 
+
 class TestOptionWithListConverter(tests.TestCase, TestOptionConverterMixin):
 
     def get_option(self):
 
=== modified file 'doc/en/release-notes/bzr-2.5.txt'
--- doc/en/release-notes/bzr-2.5.txt	2011-12-09 12:04:25 +0000
+++ doc/en/release-notes/bzr-2.5.txt	2011-12-09 16:30:32 +0000
@@ -32,6 +32,9 @@
 .. Fixes for situations where bzr would previously crash or give incorrect
    or undesirable results.
 
+* Allow configuration option default value to be a python callable at
+  registration. (Vincent Ladeuil, #832064)
+
 * Properly ignore '\n' in an option reference since this cannot be part of a
   config option identifier. (Vincent Ladeuil, #902125)