Web.Scotty

Turn a scotty application into a WAI Application, which can be run with any WAI handler.

Standard Sinatra-style route. Named captures are prepended with colons. This is the default route type generated by OverloadedString routes. i.e.

get (capture "/foo/:bar") $ ...

and

{-# LANGUAGE OverloadedStrings #-}
...
get "/foo/:bar" $ ...

are equivalent.

Match requests using a regular expression. Named captures are not yet supported.

>>> :{let server = S.get (S.regex "^/f(.*)r$") $ do                cap <- S.pathParam "1"                S.text cap in do      withScotty server $ curl "http://localhost:3000/foo/bar":}"oo/ba"

Build a route based on a function which can match using the entire Request object. Nothing indicates the route does not match. A Just value indicates a successful match, optionally returning a list of key-value pairs accessible by param.

>>> :{let server = S.get (function $ \req -> Just [("version", T.pack $ show $ W.httpVersion req)]) $ do                v <- S.pathParam "version"                S.text v in do      withScotty server $ curl "http://localhost:3000/":}"HTTP/1.1"

Build a route that requires the requested path match exactly, without captures.

Get the Request object.

Get a request header. Header name is case-insensitive.

Get all the request headers. Header names are case-insensitive.

Get the request body.

NB: loads the entire request body in memory

Get an IO action that reads body chunks

• This is incompatible with body since body consumes all chunks.

Parse the request body as a JSON object and return it. Raises an exception if parse is unsuccessful.

NB: uses body internally

Get a parameter. First looks in captures, then form data, then query parameters.

• Raises an exception which can be caught by catch if parameter is not found.

• If parameter is found, but parseParam fails to parse to the correct type, next is called. This means captures are somewhat typed, in that a route won't match if a correctly typed capture cannot be parsed.

Get all parameters from path, form and query (in that order).

Get a path parameter.

• Raises an exception which can be caught by catch if parameter is not found. If the exception is not caught, scotty will return a HTTP error code 500 ("Internal Server Error") to the client.

• If the parameter is found, but parseParam fails to parse to the correct type, next is called.

Since: 0.21

Synonym for pathParam

Since: 0.20

Get a form parameter.

• Raises an exception which can be caught by catch if parameter is not found. If the exception is not caught, scotty will return a HTTP error code 400 ("Bad Request") to the client.

• This function raises a code 400 also if the parameter is found, but parseParam fails to parse to the correct type.

Since: 0.20

Get a query parameter.

• Raises an exception which can be caught by catch if parameter is not found. If the exception is not caught, scotty will return a HTTP error code 400 ("Bad Request") to the client.

• This function raises a code 400 also if the parameter is found, but parseParam fails to parse to the correct type.

Since: 0.20

Look up a path parameter. Returns Nothing if the parameter is not found or cannot be parsed at the right type.

NB : Doesn't throw exceptions. In particular, route pattern matching will not continue, so developers must raiseStatus or throw to signal something went wrong.

Since: 0.21

Synonym for pathParamMaybe

Since: 0.21

Look up a form parameter. Returns Nothing if the parameter is not found or cannot be parsed at the right type.

NB : Doesn't throw exceptions, so developers must raiseStatus or throw to signal something went wrong.

Since: 0.21

Look up a query parameter. Returns Nothing if the parameter is not found or cannot be parsed at the right type.

NB : Doesn't throw exceptions, so developers must raiseStatus or throw to signal something went wrong.

Since: 0.21

Get path parameters

Synonym for pathParams

Get form parameters

Get query parameters

Get list of uploaded files.

NB: Loads all file contents in memory with options defaultParseRequestBodyOptions

Get list of temp files and form parameters decoded from multipart payloads.

NB the temp files are deleted when the continuation exits

A data structure that describes the behavior of the parseRequestBodyEx function.

Set the HTTP response status. Default is 200.

Add to the response headers. Header names are case-insensitive.

Set one of the response headers. Will override any previously set value for that header. Header names are case-insensitive.

Redirect to given URL. Like throwing an uncatchable exception. Any code after the call to redirect will not be run.

redirect "http://www.google.com"

OR

redirect "/foo/bar"

Set the body of the response to the given Text value. Also sets "Content-Type" header to "text/plain; charset=utf-8" if it has not already been set.

Set the body of the response to the given Text value. Also sets "Content-Type" header to "text/html; charset=utf-8" if it has not already been set.

Send a file as the response. Doesn't set the "Content-Type" header, so you probably want to do that on your own with setHeader.

Set the body of the response to the JSON encoding of the given value. Also sets "Content-Type" header to "application/json; charset=utf-8" if it has not already been set.

Set the body of the response to a StreamingBody. Doesn't set the "Content-Type" header, so you probably want to do that on your own with setHeader.

Set the body of the response to the given BL.ByteString value. Doesn't set the "Content-Type" header, so you probably want to do that on your own with setHeader.

Access the HTTP headers of the Response

Since: 0.21

Access the HTTP Status of the Response

Since: 0.21

Access the content of the Response

Since: 0.21

Throw a "500 Server Error" StatusError, which can be caught with catch.

Uncaught exceptions turn into HTTP 500 responses.

Throw a StatusError exception that has an associated HTTP error code and can be caught with catch.

Uncaught exceptions turn into HTTP responses corresponding to the given status.

Throw an exception which can be caught within the scope of the current Action with catch.

If the exception is not caught locally, another option is to implement a global Handler (with defaultHandler) that defines its interpretation and a translation to HTTP error codes.

Uncaught exceptions turn into HTTP 500 responses.

Catch an exception e.g. a StatusError or a user-defined exception.

raise JustKidding `catch` (\msg -> text msg)

Abort execution of this action and continue pattern matching routes. Like an exception, any code after next is not executed.

NB : Internally, this is implemented with an exception that can only be caught by the library, but not by the user.

As an example, these two routes overlap. The only way the second one will ever run is if the first one calls next.

get "/foo/:bar" $ do
  w :: Text <- pathParam "bar"
  unless (w == "special") next
  text "You made a request to /foo/special"

get "/foo/:baz" $ do
  w <- pathParam "baz"
  text $ "You made a request to: " <> w

Abort execution of this action. Like an exception, any code after finish is not executed.

As an example only requests to /foo/special will include in the response content the text message.

get "/foo/:bar" $ do
  w :: Text <- pathParam "bar"
  unless (w == "special") finish
  text "You made a request to /foo/special"

Since: 0.10.3

Global handler for user-defined exceptions.

Like liftIO, but catch any IO exceptions and turn them into Scotty exceptions.

Lift a computation from the IO monad. This allows us to run IO computations in any monadic stack, so long as it supports these kinds of operations (i.e. IO is the base monad for the stack).

Example

import Control.Monad.Trans.State -- from the "transformers" library

printState :: Show s => StateT s IO ()
printState = do
  state <- get
  liftIO $ print state

Had we omitted liftIO, we would have ended up with this error:

• Couldn't match type ‘IO’ with ‘StateT s IO’
 Expected type: StateT s IO ()
   Actual type: IO ()

The important part here is the mismatch between StateT s IO () and IO ().

Luckily, we know of a function that takes an IO a and returns an (m a): liftIO, enabling us to run the program and see the expected results:

> evalStateT printState "hello"
"hello"

> evalStateT printState 3
3

Catch a synchronous (but not asynchronous) exception and recover from it.

This is parameterized on the exception type. To catch all synchronous exceptions, use catchAny.

E.g. when a parameter is not found in a query string (400 Bad Request) or when parsing a JSON body fails (422 Unprocessable Entity)

Thrown e.g. when a request is too large