Safe Haskell | None |
---|---|
Language | Haskell98 |
- requires :: Combines x y => x -> y -> CombinedType x y
- before :: Combines x y => x -> y -> CombinedType x y
- onChange :: Combines x y => x -> y -> CombinedType x y
- onChangeFlagOnFail :: Combines x y => FilePath -> x -> y -> CombinedType x y
- flagFile :: Property i -> FilePath -> Property i
- flagFile' :: Property i -> IO FilePath -> Property i
- check :: LiftPropellor m => m Bool -> Property i -> Property i
- fallback :: Combines p1 p2 => p1 -> p2 -> CombinedType p1 p2
- trivial :: Property i -> Property i
- revert :: RevertableProperty i -> RevertableProperty i
- describe :: IsProp p => p -> Desc -> p
- (==>) :: IsProp (Property i) => Desc -> Property i -> Property i
- data Propellor p
- property :: Desc -> Propellor Result -> Property NoInfo
- ensureProperty :: Property NoInfo -> Propellor Result
- withOS :: Desc -> (Maybe System -> Propellor Result) -> Property NoInfo
- makeChange :: IO () -> Propellor Result
- noChange :: Propellor Result
- doNothing :: Property NoInfo
- endAction :: Desc -> (Result -> Propellor Result) -> Propellor ()
Property combinators
requires :: Combines x y => x -> y -> CombinedType x y Source
Indicates that the first property depends on the second, so before the first is ensured, the second must be ensured.
The combined property uses the description of the first property.
before :: Combines x y => x -> y -> CombinedType x y Source
Combines together two properties, resulting in one property that ensures the first, and if the first succeeds, ensures the second.
The combined property uses the description of the first property.
onChange :: Combines x y => x -> y -> CombinedType x y Source
Whenever a change has to be made for a Property, causes a hook Property to also be run, but not otherwise.
onChangeFlagOnFail :: Combines x y => FilePath -> x -> y -> CombinedType x y Source
Same as onChange
except that if property y fails, a flag file
is generated. On next run, if the flag file is present, property y
is executed even if property x doesn't change.
With onChange
, if y fails, the property x onChange
y returns
FailedChange
. But if this property is applied again, it returns
NoChange
. This behavior can cause trouble...
flagFile :: Property i -> FilePath -> Property i Source
Makes a perhaps non-idempotent Property be idempotent by using a flag file to indicate whether it has run before. Use with caution.
check :: LiftPropellor m => m Bool -> Property i -> Property i Source
Makes a Property only need to do anything when a test succeeds.
fallback :: Combines p1 p2 => p1 -> p2 -> CombinedType p1 p2 Source
Tries the first property, but if it fails to work, instead uses the second.
trivial :: Property i -> Property i Source
Marks a Property as trivial. It can only return FailedChange or NoChange.
Useful when it's just as expensive to check if a change needs to be made as it is to just idempotently assure the property is satisfied. For example, chmodding a file.
revert :: RevertableProperty i -> RevertableProperty i Source
Undoes the effect of a RevertableProperty.
Property descriptions
(==>) :: IsProp (Property i) => Desc -> Property i -> Property i infixl 1 Source
Alias for flip describe
Constructing properties
Propellor's monad provides read-only access to info about the host it's running on, and a writer to accumulate EndActions.
property :: Desc -> Propellor Result -> Property NoInfo Source
Constructs a Property, from a description and an action to run to ensure the Property is met.
ensureProperty :: Property NoInfo -> Propellor Result Source
For when code running in the Propellor monad needs to ensure a Property.
This can only be used on a Property that has NoInfo.
withOS :: Desc -> (Maybe System -> Propellor Result) -> Property NoInfo Source
Makes a property that is satisfied differently depending on the host's operating system.
Note that the operating system may not be declared for all hosts.
myproperty = withOS "foo installed" $ \o -> case o of (Just (System (Debian suite) arch)) -> ... (Just (System (Ubuntu release) arch)) -> ... Nothing -> ...
makeChange :: IO () -> Propellor Result Source