Safe Haskell	None

Heist.Compiled

Contents

High level compiled splice API
Functions for manipulating lists of compiled splices
Old compiled splice API
Constructing Chunks
Lower level promise functions
Running nodes and splices

Description

Compiled splices are similar to the original Heist (interpreted) splices, but without the high performance costs of traversing a DOM at runtime. Compiled splices do all of their DOM processing at load time. They are compiled to produce a runtime computation that generates a ByteString Builder. This preserves the ability to write splices that access runtime information from the HTTP request, database, etc.

If you import both this module and Heist.Interpreted in the same file, then you will need to import them qualified.

Synopsis

High level compiled splice API

type Splice n = HeistT n IO (DList (Chunk n))

A compiled Splice is a HeistT computation that returns a DList (Chunk m).

The more interesting part of the type signature is what comes before the return value. The first type parameter in HeistT n IO is the runtime monad. This reveals that the Chunks know about the runtime monad. The second type parameter in HeistT n IO is IO. This tells is that the compiled splices themselves are run in the IO monad, which will usually mean at load time. Compiled splices run at load time, and they return computations that run at runtime.

renderTemplate :: Monad n => HeistState n -> ByteString -> Maybe (n Builder, MIMEType)

Looks up a compiled template and returns a runtime monad computation that constructs a builder.

codeGen :: Monad n => DList (Chunk n) -> RuntimeSplice n Builder

Given a list of output chunks, consolidate turns consecutive runs of Pure Html values into maximally-efficient pre-rendered strict ByteString chunks.

runChildren :: Monad n => Splice n

Runs the parameter node's children and returns the resulting compiled chunks. By itself this function is a simple passthrough splice that makes the spliced node disappear. In combination with locally bound splices, this function makes it easier to pass the desired view into your splices.

Functions for manipulating lists of compiled splices

mapSnd :: (b -> c) -> [(d, b)] -> [(d, c)]

Helper function for transforming the second element of each of a list of tuples.

applySnd :: a -> [(d, a -> b)] -> [(d, b)]

The type signature says it all.

prefixSplices :: Text -> Text -> [(Text, a)] -> [(Text, a)]

Adds a prefix to the tag names for a list of splices. If the existing tag name is empty, then the new tag name is just the prefix. Otherwise the new tag name is the prefix followed by the separator followed by the existing name.

namespaceSplices :: Text -> [(Text, a)] -> [(Text, a)]

prefixSplices specialized to use a colon as separator in the style of XML namespaces.

textSplices :: [(Text, a -> Text)] -> [(Text, a -> Builder)]

Converts pure text splices to pure Builder splices.

nodeSplices :: [(Text, a -> [Node])] -> [(Text, a -> Builder)]

Converts pure Node splices to pure Builder splices.

pureSplices :: Monad n => [(d, a -> Builder)] -> [(d, Promise a -> Splice n)]

Converts pure Builder splices into monadic splice functions of a Promise.

textSplice :: (a -> Text) -> a -> Builder

Converts a pure text splice function to a pure Builder splice function.

nodeSplice :: (a -> [Node]) -> a -> Builder

Converts a pure Node splice function to a pure Builder splice function.

pureSplice :: Monad n => (a -> Builder) -> Promise a -> Splice n

Converts a pure Builder splice function into a monadic splice function that takes a Promise.

mapInputPromise :: Monad n => (a -> b) -> (Promise b -> Splice n) -> Promise a -> Splice n

repromise :: Monad n => (a -> n b) -> [(d, Promise b -> Splice n)] -> [(d, Promise a -> Splice n)]

Repromise a list of splices.

repromiseMay :: Monad n => (a -> n (Maybe b)) -> [(d, Promise b -> Splice n)] -> [(d, Promise a -> Splice n)]

repromiseMay' for a list of splices.

repromise' :: Monad n => (a -> n b) -> (Promise b -> Splice n) -> Promise a -> Splice n

Change the promise type of a splice function.

repromiseMay' :: Monad n => (a -> n (Maybe b)) -> (Promise b -> Splice n) -> Promise a -> Splice n

Change the promise type of a splice function with a function that might fail. If a Nothing is encountered, then the splice will generate no output.

defer :: Monad n => (Promise a -> Splice n) -> RuntimeSplice n a -> Splice n

Allows you to use deferred Promises in a compiled splice. It takes care of the boilerplate of creating and storing data in a promise to be used at load time when compiled splices are processed. This function is similar to mapPromises but runs on a single value instead of a list.

deferMany :: Monad n => (Promise a -> Splice n) -> RuntimeSplice n [a] -> Splice n

Takes a promise function and a runtime action returning a list of items that fit in the promise and returns a Splice that executes the promise function for each item and concatenates the results.

withSplices :: Monad n => Splice n -> [(Text, Promise a -> Splice n)] -> n a -> Splice n

manyWithSplices

Arguments

:: Monad n
=> Splice n	Splice to run for each of the items in the runtime list. You'll frequently use `runChildren` here.
-> [(Text, Promise a -> Splice n)]	List of splices to bind
-> n [a]	Runtime action returning a list of items to render.
-> Splice n

Gets a list of items at runtime, then for each item it runs the splice with the list of splices bound. There is no pure variant of this function because the desired behavior can only be achieved as a function of a Promise.

withPureSplices :: Monad n => Splice n -> [(Text, a -> Builder)] -> n a -> Splice n

Old compiled splice API

mapPromises

Arguments

:: Monad n
=> (Promise a -> HeistT n IO (RuntimeSplice n Builder))	Use `promiseChildrenWith` or a variant to create this function.
-> RuntimeSplice n [a]	Runtime computation returning a list of items
-> Splice n

Takes a promise function and a runtime action returning a list of items that fit in the promise and returns a Splice that executes the promise function for each item and concatenates the results.

This function works nicely with the promiseChildrenWith family of functions, much like the combination of mapSplices and runChildrenWith for interpreted splices.

promiseChildren :: Monad n => HeistT n IO (RuntimeSplice n Builder)

Returns a runtime computation that simply renders the node's children.

promiseChildrenWith :: Monad n => [(Text, a -> Builder)] -> Promise a -> HeistT n IO (RuntimeSplice n Builder)

Binds a list of Builder splices before using the children of the spliced node as a view.

promiseChildrenWithTrans :: Monad n => (b -> Builder) -> [(Text, a -> b)] -> Promise a -> HeistT n IO (RuntimeSplice n Builder)

Wrapper that composes a transformation function with the second item in each of the tuples before calling promiseChildren.

promiseChildrenWithText :: Monad n => [(Text, a -> Text)] -> Promise a -> HeistT n IO (RuntimeSplice n Builder)

Binds a list of Text splices before using the children of the spliced node as a view.

promiseChildrenWithNodes :: Monad n => [(Text, a -> [Node])] -> Promise a -> HeistT n IO (RuntimeSplice n Builder)

Binds a list of Node splices before using the children of the spliced node as a view. Note that this will slow down page generation because the nodes generated by the splices must be traversed and rendered into a ByteString at runtime.

Constructing Chunks

The internals of the Chunk data type are deliberately not exported because we want to hide the underlying implementation as much as possible. The yield... functions give you lower lever construction of Chunks and DLists of Chunks.

yieldPure :: Builder -> DList (Chunk n)

Yields a pure Builder known at load time. You should use this and yieldPureText as much as possible to maximize the parts of your page that can be compiled to static ByteStrings.

yieldRuntime :: RuntimeSplice n Builder -> DList (Chunk n)

Yields a runtime action that returns a builder.

yieldRuntimeEffect :: Monad n => RuntimeSplice n () -> DList (Chunk n)

Yields a runtime action that returns no value and is only needed for its side effect.

yieldPureText :: Text -> DList (Chunk n)

A convenience wrapper around yieldPure for working with Text. Roughly equivalent to textSplice from Heist.Interpreted.

yieldRuntimeText :: Monad n => RuntimeSplice n Text -> DList (Chunk n)

Convenience wrapper around yieldRuntime allowing you to work with Text.

yieldLater :: Monad n => n Builder -> DList (Chunk n)

This lets you turn a plain runtime monad function returning a Builder into a compiled splice.

addSplices :: Monad m => [(Text, Splice n)] -> HeistT n m ()

Adds a list of compiled splices to the splice map. This function is useful because it allows compiled splices to bind other compiled splices during load-time splice processing.

withLocalSplices :: [(Text, Splice n)] -> [(Text, AttrSplice n)] -> HeistT n IO a -> HeistT n IO a

Adds a list of compiled splices to the splice map. This function is useful because it allows compiled splices to bind other compiled splices during load-time splice processing.

Lower level promise functions

data Promise a

Promises are used for referencing the results of future runtime computations during load time splice processing.

newEmptyPromise :: HeistT n IO (Promise a)

Creates an empty promise.

getPromise :: Monad n => Promise a -> RuntimeSplice n a

Gets the result of a promised runtime computation.

putPromise :: Monad n => Promise a -> a -> RuntimeSplice n ()

Adds a promise to the runtime splice context.

adjustPromise :: Monad n => Promise a -> (a -> a) -> RuntimeSplice n ()

Modifies a promise.

Running nodes and splices

runNodeList :: Monad n => [Node] -> Splice n

Returns a computation that performs load-time splice processing on the supplied list of nodes.

runNode :: Monad n => Node -> Splice n

Runs a single node. If there is no splice referenced anywhere in the subtree, then it is rendered as a pure chunk, otherwise it calls compileNode to generate the appropriate runtime computation.

runAttributes :: Monad n => [(Text, Text)] -> HeistT n IO [DList (Chunk n)]

Performs splice processing on a list of attributes. This is useful in situations where you need to stop recursion, but still run splice processing on the node's attributes.

runAttributesRaw :: (Monad m, Monad n) => [(Text, Text)] -> HeistT n m (RuntimeSplice n [(Text, Text)])

Performs splice processing on a list of attributes. This is useful in situations where you need to stop recursion, but still run splice processing on the node's attributes.

callTemplate :: Monad n => ByteString -> HeistT n IO (DList (Chunk n))

Looks up a compiled template and returns a compiled splice.