Add Paths as first-class types in configs.

scripts/slave/recipe_config_types.py

Index: scripts/slave/recipe_config_types.py
diff --git a/scripts/slave/recipe_config_types.py b/scripts/slave/recipe_config_types.py
new file mode 100644
index 0000000000000000000000000000000000000000..08e9ff95fa1085e923a2291cfa4e99e7b9dbc2c5
--- /dev/null
+++ b/scripts/slave/recipe_config_types.py
@@ -0,0 +1,52 @@
+import re
+
+def ResetHandlers():
+  RecipeConfigType._HANDLER_MAP.clear()  # pylint: disable=W0212
+
+
+def json_fixup(obj):
+  if isinstance(obj, RecipeConfigType):
+    return str(obj)
+  raise TypeError("%r is not JSON serializable" % obj)
+
+
+class RecipeConfigType(object):

[agable, 2013/09/26 21:46:02]

docstrings docstrings docstrings.

[iannucci, 2013/09/27 02:08:20]

Done.

+  _HANDLER_MAP = {}
+
+  def handle(self):
+    return self._HANDLER_MAP.get(self.__class__.__name__,
+                                 self.__class__.default_handler)(self)
+
+  @classmethod
+  def set_handler(cls, new_handler):
+    assert cls.__name__ not in cls._HANDLER_MAP, (
+      'Handler already installed for %s' % cls)
+    cls._HANDLER_MAP[cls.__name__] = new_handler
+
+  def default_handler(self, *args, **kwargs):

[agable, 2013/09/26 21:46:02]

default_tostring maybe? Not clear what it means to "handle" an object.

[iannucci, 2013/09/27 02:08:20]

how about default_tostring_fn . Makes sense to talk about 'tostring_fn's,
talking in the docstrings about 'tostring's or 'tostring functions' is
awkwardish.

+    raise NotImplementedError
+
+  def __str__(self):
+    return self.handle()
+
+
+class Path(RecipeConfigType):
+  BASE_RE = re.compile("[a-z][a-z_]*")

[agable, 2013/09/26 21:46:02]

This RE seems incredibly restrictive. Also, (due to lack of docstrings) it's not
clear just from reading this that self.base is an alias that will get expanded
to a real base path at the last second. 

[iannucci, 2013/09/27 02:08:20]

docstrings should clear this up more, added comment to make sure.

+
+  def __init__(self, base=None, *pieces, **kwargs):
+    super(Path, self).__init__()

[agable, 2013/09/26 21:46:02]

Should pass kwargs to init. Otherwise there's no reason to have them.

[iannucci, 2013/09/27 02:08:20]

I would love to have wrapper=False at the end here, but... python 2.7 :/

+    assert '..' not in pieces
+    assert self.BASE_RE.match(base)
+
+    self.base = base
+    self.pieces = pieces
+    self.wrapper = kwargs.get('wrapper', False)

[agable, 2013/09/26 21:46:02]

Since there's only one wrapper function, and it is "append .bat if we're on
windows", this needs a better name. Either that, or it needs to be a function
that gets called as part of __str__.

[iannucci, 2013/09/27 02:08:20]

Ok, changed this to a more generic fixed-function 'platform_ext'.

+
+  def __call__(self, *pieces, **kwargs):
+    wrapper = kwargs.get('wrapper', self.wrapper)
+    new_pieces = filter(bool, self.pieces + pieces)
+    return Path(self.base, *new_pieces, wrapper=wrapper)
+
+  def default_handler(self):
+    suffix = ', wrapper=True' if self.wrapper else ''
+    return 'Path([%s], %r%s)' % (self.base.upper(), self.pieces, suffix)

[agable, 2013/09/26 21:58:08]

Path([ROOT], piece, piece, piece) looks better than PATH([ROOT], (piece, piece,
piece)).

[iannucci, 2013/09/27 02:09:20]

Since I changed the signature of this class, I decided to leave this alone...
can still do it if you like.