Rev 5756: Better explain lazy loading and make sure the mutable section respect the design. in file:///home/vila/src/bzr/experimental/config/

[Vincent Ladeuil]

At file:///home/vila/src/bzr/experimental/config/

------------------------------------------------------------
revno: 5756
revision-id: v.ladeuil+lp at free.fr-20110406091148-30rdyrxq0c3odhrz
parent: v.ladeuil+lp at free.fr-20110406082436-1d0css49ccsb6vc2
committer: Vincent Ladeuil <v.ladeuil+lp at free.fr>
branch nick: config-stack
timestamp: Wed 2011-04-06 11:11:48 +0200
message:
  Better explain lazy loading and make sure the mutable section respect the design.
-------------- next part --------------
=== modified file 'bzrlib/config.py'
--- a/bzrlib/config.py	2011-04-06 08:24:36 +0000
+++ b/bzrlib/config.py	2011-04-06 09:11:48 +0000
@@ -2183,19 +2183,27 @@
 class ConfigStack(object):
     """A stack of configurations where an option can be defined"""
 
-    def __init__(self, sections, mutable_section=None):
+    def __init__(self, sections, get_mutable_section=None):
         """Creates a stack of sections with an optional store for changes.
 
         :param sections: A list of ReadOnlySection or callables that returns an
             iterable of ReadOnlySection.
 
-        :param mutable_section: A MutableSection where changes are recorded.
+        :param get_mutable_section: A callable that returns a MutableSection
+            where changes are recorded.
         """
         self.sections = sections
-        self.mutable_section = mutable_section
+        self.get_mutable_section = get_mutable_section
 
     def get(self, name):
-        """Return the value from the first definition found in the sections"""
+        """Return the value from the first definition found in the sections.
+
+        This is where we guarantee that sections coming from Store lazily load
+        them: the loading is delayed until we need to either check that an
+        option exists or get its value, which in turn may require to discover
+        in which sections it can be defined. Both of these (section and option
+        existence) require loading the store (even partially).
+        """
         for section_or_callable in self.sections:
             # Each section can expand to multiple ones when a callable is used
             if callable(section_or_callable):
@@ -2210,7 +2218,13 @@
         return None
 
     def set(self, name, value):
-        self.mutable_section.set(name, value)
+        """Set a new value for the option.
+
+        This where we guarantee that the mutable section is lazily loaded: this
+        means we won't load the correspoding store before setting a value.
+        """
+        section = self.get_mutable_section()
+        section.set(name, value)
 
 
 class cmd_config(commands.Command):

=== modified file 'bzrlib/tests/test_config.py'
--- a/bzrlib/tests/test_config.py	2011-04-06 07:59:42 +0000
+++ b/bzrlib/tests/test_config.py	2011-04-06 09:11:48 +0000
@@ -2069,7 +2069,7 @@
         store = config.ConfigObjStore.from_string(
             'foo=bar', self.get_transport(), 'test.conf')
         conf = config.ConfigStack(
-            [store.get_sections], store.get_mutable_section(None))
+            [store.get_sections], store.get_mutable_section)
         self.assertEquals('bar', conf.get('foo'))
         conf.set('foo', 'baz')
         # Did we get it back ?
@@ -2079,7 +2079,7 @@
         store = config.ConfigObjStore.from_string(
             '', self.get_transport(), 'test.conf')
         conf = config.ConfigStack(
-            [store.get_sections], store.get_mutable_section(None))
+            [store.get_sections], store.get_mutable_section)
         conf.set('foo', 'baz')
         self.assertEquals, 'baz', conf.get('foo')