Property tree

Properties now form a tree, instead of the flat list used before.

This simplifies propigation of Info from the Properties used inside a
container to the outer host; the Property that docks the container on the
host can just have as child properties all the inner Properties, and their
Info can then be gathered recursively. (Although in practice it still needs
to be filtered, since not all Info should propigate out of a container.)

Note that there is no change to how Properties are actually satisfied.
Just because a Property lists some child properties, this does not mean
they always have their propertySatisfy actions run. It's still up to the
parent property to run those actions.

That's necessary so that a container's properties can be satisfied inside
it, not outside. It also allows property combinators to
add the combined Properties to their childProperties list, even if,
like onChange, they don't always run the child properties at all.

Testing: I tested that the exact same Info is calculated before and after
this change, for every Host in my config file.

1 files changed, 7 insertions, 13 deletions

diff --git a/src/Propellor/Property.hs b/src/Propellor/Property.hs
index c0878fb6..43690735 100644
--- a/src/Propellor/Property.hs
+++ b/src/Propellor/Property.hs
@@ -16,19 +16,19 @@ import Utility.Monad
 
 -- Constructs a Property.
 property :: Desc -> Propellor Result -> Property
-property d s = Property d s mempty
+property d s = Property d s mempty mempty
 
 -- | Combines a list of properties, resulting in a single property
 -- that when run will run each property in the list in turn,
 -- and print out the description of each as it's run. Does not stop
 -- on failure; does propigate overall success/failure.
 propertyList :: Desc -> [Property] -> Property
-propertyList desc ps = Property desc (ensureProperties ps) (combineInfos ps)
+propertyList desc ps = Property desc (ensureProperties ps) mempty ps
 
 -- | Combines a list of properties, resulting in one property that
 -- ensures each in turn. Stops if a property fails.
 combineProperties :: Desc -> [Property] -> Property
-combineProperties desc ps = Property desc (go ps NoChange) (combineInfos ps)
+combineProperties desc ps = Property desc (go ps NoChange) mempty ps
   where
 	go [] rs = return rs
 	go (l:ls) rs = do
@@ -67,15 +67,16 @@ flagFile' p getflagfile = adjustProperty p $ \satisfy -> do
 --- | Whenever a change has to be made for a Property, causes a hook
 -- Property to also be run, but not otherwise.
 onChange :: Property -> Property -> Property
-p `onChange` hook = Property (propertyDesc p) satisfy (combineInfo p hook)
-  where
-	satisfy = do
+p `onChange` hook = p
+	{ propertySatisfy = do
 		r <- ensureProperty p
 		case r of
 			MadeChange -> do
 				r' <- ensureProperty hook
 				return $ r <> r'
 			_ -> return r
+	, propertyChildren = propertyChildren p ++ [hook]
+	}
 
 (==>) :: Desc -> Property -> Property
 (==>) = flip describe
@@ -128,13 +129,6 @@ revert (RevertableProperty p1 p2) = RevertableProperty p2 p1
 adjustProperty :: Property -> (Propellor Result -> Propellor Result) -> Property
 adjustProperty p f = p { propertySatisfy = f (propertySatisfy p) }
 
--- | Combines the Info of two properties.
-combineInfo :: (IsProp p, IsProp q) => p -> q -> Info
-combineInfo p q = getInfo p <> getInfo q
-
-combineInfos :: IsProp p => [p] -> Info
-combineInfos = mconcat . map getInfo
-
 makeChange :: IO () -> Propellor Result
 makeChange a = liftIO a >> return MadeChange