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authorJoey Hess2016-03-28 05:53:38 -0400
committerJoey Hess2016-03-28 05:55:48 -0400
commita1655d24bbb1db9caccdf93eae8110d746389ae2 (patch)
tree66b6890d852c19daec2306920fecf9108e055273 /src/Propellor/Types/Core.hs
parentebf30061d8f8a251330070e69c2710fe4a8fd9da (diff)
type safe targets for properties
* Property types have been improved to indicate what systems they target. This prevents using eg, Property FreeBSD on a Debian system. Transition guide for this sweeping API change: - Change "host name & foo & bar" to "host name $ props & foo & bar" - Similarly, `propertyList` and `combineProperties` need `props` to be used to combine together properties; they no longer accept lists of properties. (If you have such a list, use `toProps`.) - And similarly, Chroot, Docker, and Systemd container need `props` to be used to combine together the properies used inside them. - The `os` property is removed. Instead use `osDebian`, `osBuntish`, or `osFreeBSD`. These tell the type checker the target OS of a host. - Change "Property NoInfo" to "Property UnixLike" - Change "Property HasInfo" to "Property (HasInfo + UnixLike)" - Change "RevertableProperty NoInfo" to "RevertableProperty UnixLike UnixLike" - Change "RevertableProperty HasInfo" to "RevertableProperty (HasInfo + UnixLike) UnixLike" - GHC needs {-# LANGUAGE TypeOperators #-} to use these fancy types. This is enabled by default for all modules in propellor.cabal. But if you are using propellor as a library, you may need to enable it manually. - If you know a property only works on a particular OS, like Debian or FreeBSD, use that instead of "UnixLike". For example: "Property Debian" - It's also possible make a property support a set of OS's, for example: "Property (Debian + FreeBSD)" - Removed `infoProperty` and `simpleProperty` constructors, instead use `property` to construct a Property. - Due to the polymorphic type returned by `property`, additional type signatures tend to be needed when using it. For example, this will fail to type check, because the type checker cannot guess what type you intend the intermediate property "go" to have: foo :: Property UnixLike foo = go `requires` bar where go = property "foo" (return NoChange) To fix, specify the type of go: go :: Property UnixLike - `ensureProperty` now needs to be passed a witness to the type of the property it's used in. change this: foo = property desc $ ... ensureProperty bar to this: foo = property' desc $ \w -> ... ensureProperty w bar - General purpose properties like cmdProperty have type "Property UnixLike". When using that to run a command only available on Debian, you can tighten the type to only the OS that your more specific property works on. For example: upgraded :: Property Debian upgraded = tightenTargets (cmdProperty "apt-get" ["upgrade"]) - Several utility functions have been renamed: getInfo to fromInfo propertyInfo to getInfo propertyDesc to getDesc propertyChildren to getChildren * The new `pickOS` property combinator can be used to combine different properties, supporting different OS's, into one Property that chooses which to use based on the Host's OS. * Re-enabled -O0 in propellor.cabal to reign in ghc's memory use handling these complex new types. * Added dependency on concurrent-output; removed embedded copy.
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+{-# LANGUAGE PackageImports #-}
+{-# LANGUAGE GeneralizedNewtypeDeriving #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE FlexibleInstances #-}
+
+module Propellor.Types.Core where
+
+import Propellor.Types.Info
+import Propellor.Types.OS
+import Propellor.Types.Result
+
+import Data.Monoid
+import "mtl" Control.Monad.RWS.Strict
+import Control.Monad.Catch
+import Control.Applicative
+import Prelude
+
+-- | Everything Propellor knows about a system: Its hostname,
+-- properties and their collected info.
+data Host = Host
+ { hostName :: HostName
+ , hostProperties :: [ChildProperty]
+ , hostInfo :: Info
+ }
+ deriving (Show, Typeable)
+
+-- | Propellor's monad provides read-only access to info about the host
+-- it's running on, and a writer to accumulate EndActions.
+newtype Propellor p = Propellor { runWithHost :: RWST Host [EndAction] () IO p }
+ deriving
+ ( Monad
+ , Functor
+ , Applicative
+ , MonadReader Host
+ , MonadWriter [EndAction]
+ , MonadIO
+ , MonadCatch
+ , MonadThrow
+ , MonadMask
+ )
+
+class LiftPropellor m where
+ liftPropellor :: m a -> Propellor a
+
+instance LiftPropellor Propellor where
+ liftPropellor = id
+
+instance LiftPropellor IO where
+ liftPropellor = liftIO
+
+instance Monoid (Propellor Result) where
+ mempty = return NoChange
+ -- | The second action is only run if the first action does not fail.
+ mappend x y = do
+ rx <- x
+ case rx of
+ FailedChange -> return FailedChange
+ _ -> do
+ ry <- y
+ return (rx <> ry)
+
+-- | An action that Propellor runs at the end, after trying to satisfy all
+-- properties. It's passed the combined Result of the entire Propellor run.
+data EndAction = EndAction Desc (Result -> Propellor Result)
+
+type Desc = String
+
+-- | Props is a combination of a list of properties, with their combined
+-- metatypes.
+data Props metatypes = Props [ChildProperty]
+
+-- | Since there are many different types of Properties, they cannot be put
+-- into a list. The simplified ChildProperty can be put into a list.
+data ChildProperty = ChildProperty Desc (Propellor Result) Info [ChildProperty]
+
+instance Show ChildProperty where
+ show = getDesc
+
+class IsProp p where
+ setDesc :: p -> Desc -> p
+ getDesc :: p -> Desc
+ getChildren :: p -> [ChildProperty]
+ addChildren :: p -> [ChildProperty] -> p
+ -- | Gets the info of the property, combined with all info
+ -- of all children properties.
+ getInfoRecursive :: p -> Info
+ -- | Info, not including info from children.
+ getInfo :: p -> Info
+ -- | Gets a ChildProperty representing the Property.
+ -- You should not normally need to use this.
+ toChildProperty :: p -> ChildProperty
+ -- | Gets the action that can be run to satisfy a Property.
+ -- You should never run this action directly. Use
+ -- 'Propellor.EnsureProperty.ensureProperty` instead.
+ getSatisfy :: p -> Propellor Result
+
+instance IsProp ChildProperty where
+ setDesc (ChildProperty _ a i c) d = ChildProperty d a i c
+ getDesc (ChildProperty d _ _ _) = d
+ getChildren (ChildProperty _ _ _ c) = c
+ addChildren (ChildProperty d a i c) c' = ChildProperty d a i (c ++ c')
+ getInfoRecursive (ChildProperty _ _ i c) =
+ i <> mconcat (map getInfoRecursive c)
+ getInfo (ChildProperty _ _ i _) = i
+ toChildProperty = id
+ getSatisfy (ChildProperty _ a _ _) = a