Propellor.EnsureProperty

Documentation

ensureProperty :: EnsurePropertyAllowed inner outer => OuterMetaTypesWitness outer -> Property (MetaTypes inner) -> Propellor Result

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.

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

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

data OuterMetaTypesWitness metatypes

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

type family EnsurePropertyAllowed inner outer :: Constraint where ...

Equations

EnsurePropertyAllowed inner outer = 'True ~ (EnsurePropertyNoInfo inner && EnsurePropertyTargetOSMatches inner outer)