Haskell combinator library for defining and serving web services.
Questions tagged [servant]
197 questions
6
votes
2 answers
Either computations in servant handler
A servant-server Handler is a newtype wrapper over an ExceptT, and has instances for MonadThrow, MonadCatch, MonadError, etc.
This might be a somewhat contrived example, but it shows an issue I often face:
In a handler I want to call three functions…
beta
- 2,380
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6
votes
1 answer
Using Authentication With a Custom Reader Monad With Servant
An API protected with Basic Authentication
type SubApi = API1 :<|> API2 :<|> API3
type API = BasicAuth "foo-realm" AuthData :> SubApi
supports handlers of type AuthData -> Handler a.
I have a set of handlers:
handler1 :: Request1 -> AuthMonad…
ewestern
- 293
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- 7
5
votes
1 answer
Using Servant, Selda, and SQLite together
I have been using Haskell for a year or so, and it is fantastic. I have recently started using Servant; and I would like to use an SQL-library such as Selda, so that everything is type-safe. (This is truely incredible when combined with Elm! :)…
user2633351
- 173
- 4
5
votes
1 answer
Haskell Servant (Client) - GET Request with headers
I'm trying to replicate this curl request with Haskell Servant
curl -v -H 'Accept: application/vnd.twitchtv.v5+json' \
-H 'Client-ID: someapikey' \
-X GET…
distro.obs
- 181
- 9
5
votes
1 answer
Html page in Servant -- how to combine REST API and static html pages?
I have a simple hello world Servant application. I need to add some static or dynamic html pages to it. How can I do that? In the documentation it's not mentioned. Note I don't want to create a html layout in Haskell code, I want Haskell to show the…
user266003
5
votes
1 answer
How to add a prefix to all the end points in Servant?
I have kind of a hello world app in Haskell servant, here's a part of it:
type API =
"my_items" :> Get '[JSON] [MyItem]
:<|> "my_items" :> Capture "id" Int :> Get '[JSON] MyItem
-- ...................
and the urls are:
localhost/my_items
…
Alan Coromano
- 24,958
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4
votes
1 answer
Inspecting records whose fields' types are the result of type-level computations
This came up in the context of the servant library, but the issue reappears in other contexts.
Servant allows you to define named routes using a record, like this:
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE…
danidiaz
- 26,936
- 4
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- 95
4
votes
1 answer
Haskell Servant: Construct URL from API
Suppose we have this simple API:
type FooAPI
= "foo"
:> QueryParam "age" Int
:> Get '[PlainText] Text
Is there a way to link type-level servant's API with a function that will generate URL for it? Like
someMagicFunction :: Proxy api ->…
wspbr
- 137
- 4
4
votes
1 answer
Filter the parts of a Request Path which match against a Static Segment in Servant
Supposing I'm running a Servant webserver, with two endpoints, with a type looking like this:
type BookAPI =
"books" :> Get '[JSON] (Map Text Text)
:<|> "book" :> Capture "Name" Text :> ReqBody '[JSON] (Text) :> Post '[JSON]…
Joe
- 1,479
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4
votes
0 answers
Haskell, Generic method of creating Html forms
I am building a site in Servant, and was wondering if it wouldn't be possible to create a Generic instance for generating input fields.
What I want, is to have a
class ToInputField a where
toInputField :: a -> InputField
Such that, an example…
Chris Wohlert
- 610
- 3
- 12
4
votes
1 answer
How to handle exception within a servant handler monad?
I want to handle a database exception inside a servant handler monad.
I've tried to use the try function from the Control.Exception package to be able to case match with Left exception -> throwError err422 { errBody = ... }.
I'm using…
fernandomrtnz
- 43
- 3
4
votes
1 answer
How can I use log-warper with Servant?
I have an application built on top of Servant, and now I want to add logging to the application. I skimmed through Haskell log packages, and I assume this one provides what I need:…
fycth
- 3,410
- 25
- 37
4
votes
1 answer
Servant cookie minimal example
Can anyone please provide me with a minimal example of cookies with servant-server, wai, warp, etc.?
For example, a cookie with a single field "language" with value "en"
Is there an easy way like happstack-lite addCookies and lookCookieValue?
RamiroPastor
- 1,085
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4
votes
1 answer
haskell webframeworks speed, GHCi vs Compiled
Today I did little benchmarking on my local machine to compare plain text speed of different Haskell web frameworks, and I noticed something strange. Almost all the frameworks that I tested, performed better when they were run from GHCi compared to…
milad zahedi
- 787
- 6
- 21
4
votes
3 answers
Haskell Servant Get Current Route / URL From Handler
I'd like to get current route that corresponds to my handler. Here is mockup of my server just for reference:
type ServerAPI =
"route01" :> Get '[HTML] Text
:<|> "route02" :> "subroute" :> Get '[HTML] Text
:<|> "route03" :> Get…
Reygoch
- 1,204
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