servant-server-0.7: A family of combinators for defining webservices APIs and serving them

Safe HaskellNone




data Router' env a Source

Internal representation of a router.

The first argument describes an environment type that is expected as extra input by the routers at the leaves. The environment is filled while running the router, with path components that can be used to process captures.


StaticRouter (Map Text (Router' env a)) [env -> a]

the map contains routers for subpaths (first path component used for lookup and removed afterwards), the list contains handlers for the empty path, to be tried in order

CaptureRouter (Router' (Text, env) a)

first path component is passed to the child router in its environment and removed afterwards

RawRouter (env -> a)

to be used for routes we do not know anything about

Choice (Router' env a) (Router' env a)

left-biased choice between two routers


pathRouter :: Text -> Router' env a -> Router' env a Source

Smart constructor for a single static path component.

leafRouter :: (env -> a) -> Router' env a Source

Smart constructor for a leaf, i.e., a router that expects the empty path.

choice :: Router' env a -> Router' env a -> Router' env a Source

Smart constructor for the choice between routers. We currently optimize the following cases:

  • Two static routers can be joined by joining their maps and concatenating their leaf-lists.
  • Two dynamic routers can be joined by joining their codomains.
  • Choice nodes can be reordered.

data RouterStructure Source

Datatype used for representing and debugging the structure of a router. Abstracts from the handlers at the leaves.

Two Routers can be structurally compared by computing their RouterStructure using routerStructure and then testing for equality, see sameStructure.

routerStructure :: Router' env a -> RouterStructure Source

Compute the structure of a router.

Assumes that the request or text being passed in WithRequest or CaptureRouter does not affect the structure of the underlying tree.

sameStructure :: Router' env a -> Router' env b -> Bool Source

Compare the structure of two routers.

routerLayout :: Router' env a -> Text Source

Provide a textual representation of the structure of a router.

tweakResponse :: (RouteResult Response -> RouteResult Response) -> Router env -> Router env Source

Apply a transformation to the response of a Router.

runRouter :: Router () -> RoutingApplication Source

Interpret a router as an application.

runChoice :: [env -> RoutingApplication] -> env -> RoutingApplication Source

Try a list of routing applications in order. We stop as soon as one fails fatally or succeeds. If all fail normally, we pick the "best" error.