shake-0.14.3: Build system library, like Make, but more accurate dependencies.

Safe HaskellNone




This module is used for defining new types of rules for Shake build systems. Most users will find the built-in set of rules sufficient.



type ShakeValue a = (Show a, Typeable a, Eq a, Hashable a, Binary a, NFData a) Source

Define an alias for the six type classes required for things involved in Shake Rules. This alias is only available in GHC 7.4 and above, and requires the ConstraintKinds extension.

To define your own values meeting the necessary constraints it is convenient to use the extensions GeneralizedNewtypeDeriving and DeriveDataTypeable to write:

newtype MyType = MyType (String, Bool) deriving (Show,Typeable,Eq,Hashable,Binary,NFData)

class (ShakeValue key, ShakeValue value) => Rule key value where Source

Define a pair of types that can be used by Shake rules. To import all the type classes required see Development.Shake.Classes.

Minimal complete definition



storedValue :: ShakeOptions -> key -> IO (Maybe value) Source

[Required] Retrieve the value associated with a key, if available.

As an example for filenames/timestamps, if the file exists you should return Just the timestamp, but otherwise return Nothing. For rules whose values are not stored externally, storedValue should return Nothing.

equalValue :: ShakeOptions -> key -> value -> value -> EqualCost Source

[Optional] Equality check, with a notion of how expensive the check was.

data EqualCost Source

An equality check and a cost.



The equality check was cheap.


The equality check was expensive, as the results are not trivially equal.


The values are not equal.

rule :: Rule key value => (key -> Maybe (Action value)) -> Rules () Source

Add a rule to build a key, returning an appropriate Action. All rules at a given priority must be disjoint. Rules have priority 1 by default, but can be modified with priority.

apply :: Rule key value => [key] -> Action [value] Source

Execute a rule, returning the associated values. If possible, the rules will be run in parallel. This function requires that appropriate rules have been added with rule. All key values passed to apply become dependencies of the Action.

apply1 :: Rule key value => key -> Action value Source

Apply a single rule, equivalent to calling apply with a singleton list. Where possible, use apply to allow parallelism.

trackUse :: ShakeValue key => key -> Action () Source

Track that a key has been used by the action preceeding it.

trackChange :: ShakeValue key => key -> Action () Source

Track that a key has been changed by the action preceeding it.

trackAllow :: ShakeValue key => (key -> Bool) -> Action () Source

Allow any matching key to violate the tracking rules.


defaultRule :: Rule key value => (key -> Maybe (Action value)) -> Rules () Source

Deprecated: Use rule with priority 0

A deprecated way of defining a low priority rule. Defined as:

defaultRule = priority 0 . rule