GADT properties seem to work (untested)

* Property has been converted to a GADT, and will be Property NoInfo
  or Property HasInfo.
  This was done to make sure that ensureProperty is only used on
  properties that do not have Info.
  Transition guide:
  - Change all "Property" to "Property NoInfo" or "Property WithInfo"
    (The compiler can tell you if you got it wrong!)
  - To construct a RevertableProperty, it is useful to use the new
    (<!>) operator
  - Constructing a list of properties can be problimatic, since
    Property NoInto and Property WithInfo are different types and cannot
    appear in the same list. To deal with this, "props" has been added,
    and can built up a list of properties of different types,
    using the same (&) and (!) operators that are used to build
    up a host's properties.

1 files changed, 25 insertions, 8 deletions

diff --git a/src/Propellor/PropAccum.hs b/src/Propellor/PropAccum.hs
index ddbc1e66..139f1471 100644
--- a/src/Propellor/PropAccum.hs
+++ b/src/Propellor/PropAccum.hs
@@ -16,6 +16,15 @@ import Propellor.Property
 host :: HostName -> Host
 host hn = Host hn [] mempty
 
+-- | Starts accumulating a list of properties.
+--
+-- > propertyList "foo" $ props
+-- > 	& someproperty
+-- > 	! oldproperty
+-- > 	& otherproperty
+props :: PropList
+props = PropList []
+
 -- | Something that can accumulate properties.
 class PropAccum h where
 	-- | Adds a property.
@@ -23,13 +32,10 @@ class PropAccum h where
 	-- Can add Properties and RevertableProperties
 	(&) :: IsProp p => h -> p -> h
 
-	-- | Like (&), but adds the property as the
-	-- first property of the host. Normally, property
-	-- order should not matter, but this is useful
-	-- when it does.
+	-- | Like (&), but adds the property at the front of the list.
 	(&^) :: IsProp p => h -> p -> h
 
-	getProperties :: h -> [Property]
+	getProperties :: h -> [Property HasInfo]
 
 instance PropAccum Host where
 	(Host hn ps is) &  p = Host hn (ps ++ [toProp p])
@@ -38,6 +44,13 @@ instance PropAccum Host where
 		(getInfoRecursive p <> is)
 	getProperties = hostProperties
 
+data PropList = PropList [Property HasInfo]
+
+instance PropAccum PropList where
+	PropList l &  p = PropList (l ++ [toProp p])
+	PropList l &^ p = PropList ([toProp p] ++ l)
+	getProperties (PropList l) = l
+
 -- | Adds a property in reverted form.
 (!) :: PropAccum h => h -> RevertableProperty -> h
 h ! p = h & revert p
@@ -57,8 +70,12 @@ infixl 1 !
 --
 -- PrivData Info is propigated, so that properties used inside a
 -- PropAccum will have the necessary PrivData available.
-propigateContainer :: PropAccum container => container -> Property -> Property
-propigateContainer c prop = mkProperty
+propigateContainer
+	:: (PropAccum container)
+	=> container
+	-> Property HasInfo
+	-> Property HasInfo
+propigateContainer c prop = infoProperty
 	(propertyDesc prop)
 	(propertySatisfy prop)
 	(propertyInfo prop)
@@ -72,4 +89,4 @@ propigateContainer c prop = mkProperty
 			, _privData = _privData i
 			}
 		    cs = map go (propertyChildren p)
-		in mkProperty (propertyDesc p) (propertySatisfy p) i' cs
+		in infoProperty (propertyDesc p) (propertySatisfy p) i' cs