propellor-4.3.3: property-based host configuration management in haskell

Propellor.Property

Synopsis

# 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...

Makes a perhaps non-idempotent Property be idempotent by using a flag file to indicate whether it has run before. Use with caution.

check :: (Checkable p i, LiftPropellor m) => m Bool -> p i -> Property i Source #

Makes a Property or an UncheckedProperty only run 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.

revert :: RevertableProperty setup undo -> RevertableProperty undo setup Source #

Undoes the effect of a RevertableProperty.

# Property descriptions

describe :: IsProp p => p -> Desc -> p Source #

Changes the description of a property.

(==>) :: IsProp (Property i) => Desc -> Property i -> Property i infixl 1 Source #

Alias for flip describe

# Constructing properties

data Propellor p Source #

Instances

 Source # Methods(>>=) :: Propellor a -> (a -> Propellor b) -> Propellor b #(>>) :: Propellor a -> Propellor b -> Propellor b #return :: a -> Propellor a #fail :: String -> Propellor a # Source # Methodsfmap :: (a -> b) -> Propellor a -> Propellor b #(<$) :: a -> Propellor b -> Propellor a # Source # Methodspure :: a -> Propellor a #(<*>) :: Propellor (a -> b) -> Propellor a -> Propellor b #(*>) :: Propellor a -> Propellor b -> Propellor b #(<*) :: Propellor a -> Propellor b -> Propellor a # Source # MethodsliftIO :: IO a -> Propellor a # Source # MethodsthrowM :: Exception e => e -> Propellor a # Source # Methodscatch :: Exception e => Propellor a -> (e -> Propellor a) -> Propellor a # Source # Methodsmask :: ((forall a. Propellor a -> Propellor a) -> Propellor b) -> Propellor b #uninterruptibleMask :: ((forall a. Propellor a -> Propellor a) -> Propellor b) -> Propellor b # Source # Methods Source # Methodslocal :: (Host -> Host) -> Propellor a -> Propellor a #reader :: (Host -> a) -> Propellor a # Source # When two actions are appended together, the second action is only run if the first action does not fail. Methods Source # Methodswriter :: (a, [EndAction]) -> Propellor a #tell :: [EndAction] -> Propellor () #listen :: Propellor a -> Propellor (a, [EndAction]) #pass :: Propellor (a, [EndAction] -> [EndAction]) -> Propellor a # property :: SingI metatypes => Desc -> Propellor Result -> Property (MetaTypes metatypes) Source # Constructs a Property, from a description and an action to run to ensure the Property is met. Due to the polymorphic return type of this function, most uses will need to specify a type signature. This lets you specify what OS the property targets, etc. For example:  foo :: Property Debian foo = property "foo"$ do
...
return MadeChange

property' :: SingI metatypes => Desc -> (OuterMetaTypesWitness metatypes -> Propellor Result) -> Property (MetaTypes metatypes) Source #

Constructs a property, like property, but provides its OuterMetaTypesWitness.

data OuterMetaTypesWitness metatypes Source #

Used to provide the metatypes of a Property to calls to ensureProperty within it.

ensureProperty :: (Cannot_ensureProperty_WithInfo inner ~ True, (Targets inner NotSuperset Targets outer) ~ CanCombine) => OuterMetaTypesWitness outer -> Property (MetaTypes inner) -> Propellor Result Source #

For when code running in the Propellor monad needs to ensure a Property.

Use property' to get the OuterMetaTypesWithness. For example:

foo = Property Debian
foo = property' "my property" $\w -> do ensureProperty w (aptInstall "foo") The type checker will prevent using ensureProperty with a property that does not support the target OSes needed by the OuterMetaTypesWitness. In the example above, aptInstall must support Debian, since foo is supposed to support Debian. The type checker will also prevent using ensureProperty with a property with HasInfo in its MetaTypes. Doing so would cause the Info associated with the property to be lost. pickOS :: (SingKind (KProxy :: KProxy ka), SingKind (KProxy :: KProxy kb), DemoteRep (KProxy :: KProxy ka) ~ [MetaType], DemoteRep (KProxy :: KProxy kb) ~ [MetaType], SingI c) => Property (MetaTypes (a :: ka)) -> Property (MetaTypes (b :: kb)) -> Property (MetaTypes c) Source # Picks one of the two input properties to use, depending on the targeted OS. If both input properties support the targeted OS, then the first will be used. The resulting property will use the description of the first property no matter which property is used in the end. So, it's often a good idea to change the description to something clearer. For example: upgraded :: Property (DebianLike + FreeBSD) upgraded = (Apt.upgraded pickOS Pkg.upgraded) describe "OS upgraded" If neither input property supports the targeted OS, calls unsupportedOS. Using the example above on a Fedora system would fail that way. withOS :: SingI metatypes => Desc -> (OuterMetaTypesWitness '[] -> Maybe System -> Propellor Result) -> Property (MetaTypes metatypes) Source # Makes a property that is satisfied differently depending on specifics of the host's operating system.  myproperty :: Property Debian myproperty = withOS "foo installed"$ \w o -> case o of
(Just (System (Debian kernel (Stable release)) arch)) -> ensureProperty w ...
(Just (System (Debian kernel suite) arch)) -> ensureProperty w ...
_ -> unsupportedOS'

Note that the operating system specifics may not be declared for all hosts, which is where Nothing comes in.

A property that always fails with an unsupported OS error.

Throws an error, for use in withOS when a property is lacking support for an OS.

A no-op property.

This is the same as mempty from the Monoid instance.

endAction :: Desc -> (Result -> Propellor Result) -> Propellor () Source #

Registers an action that should be run at the very end, after propellor has checks all the properties of a host.

# Property result checking

This is a Property but its Result is not accurate; in particular it may return NoChange despite having made a change.

However, when it returns MadeChange, it really did make a change, and FailedChange is still an error.

Instances

 Source # MethodstightenTargets :: ((CheckCombine ~ NotSuperset a (Targets a untightened) (Targets a tightened)) CanCombine, (CheckCombine ~ NotSuperset a (NonTargets a tightened) (NonTargets a untightened)) CanCombine, SingI [a] tightened) => UncheckedProperty (MetaTypes [a] untightened) -> UncheckedProperty (MetaTypes [a] tightened) Source # Source # Methods

Use to indicate that a Property is unchecked.

changesFile :: Checkable p i => p i -> FilePath -> Property i Source #

Indicates that a Property may change a particular file. When the file is modified in any way (including changing its permissions or mtime), the property will return MadeChange instead of NoChange.

changesFileContent :: Checkable p i => p i -> FilePath -> Property i Source #

Like changesFile, but compares the content of the file. Changes to mtime etc that do not change file content are treated as NoChange.

Determines if the first file is newer than the second file.

This can be used with check to only run a command when a file has changed.

check ("/etc/aliases" isNewerThan "/etc/aliases.db")
(cmdProperty "newaliases" [] assume MadeChange) -- updates aliases.db

Or it can be used with checkResult to test if a command made a change.

checkResult (return ())
(\_ -> "/etc/aliases.db" isNewerThan "/etc/aliases")
(cmdProperty "newaliases" [])

(If one of the files does not exist, the file that does exist is considered to be the newer of the two.)

Arguments

 :: (Checkable p i, LiftPropellor m) => m a Run before ensuring the property. -> (a -> m Result) Run after ensuring the property. Return MadeChange if a change was detected, or NoChange if no change was detected. -> p i -> Property i

Checks the result of a property. Mostly used to convert a UncheckedProperty to a Property, but can also be used to further check a Property.

class Checkable p i Source #

Minimal complete definition

checkedProp, preCheckedProp

Instances

 Source # MethodscheckedProp :: Property i -> Property i Source # Methods

assume :: Checkable p i => p i -> Result -> Property i Source #

Sometimes it's not practical to test if a property made a change. In such a case, it's often fine to say:

someprop assume MadeChange

However, beware assuming NoChange, as that will make combinators like onChange not work.