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config-schema
=============
[](https://hackage.haskell.org/package/config-schema) [](http://travis-ci.org/glguy/config-schema)
Live Demo
--------
The config-value and config-schema packages are available in a [live demo](https://glguy.net/config-demo/).
About
--------
This package allows the user to define configuration schemas suitable for
matching against configuration files written in the
[config-value](https://hackage.haskell.org/package/config-value) format.
These schemas allow the user to extract an arbitrary Haskell value from
an interpretation of a configuration file. It also allows the user to
programatically generate documentation for the configuration files
accepted by the loader.
```haskell
{-# Language OverloadedStrings, ApplicativeDo #-}
module Example where
import qualified Data.Text as Text
import Data.Text (Text)
import Data.Monoid ((<>))
import Data.Functor.Alt ((<!>))
import Data.List.NonEmpty (NonEmpty)
import Config
import Config.Schema
exampleFile :: Text
exampleFile =
" name: \"Johny Appleseed\" \n\
\ age : 99 \n\
\ happy: yes \n\
\ kids: \n\
\ * name: \"Bob\" \n\
\ * name: \"Tom\" \n"
exampleValue :: Value Position
Right exampleValue = parse exampleFile
exampleSpec :: ValueSpec Text
exampleSpec = sectionsSpec "" $
do name <- reqSection "name" "Full name"
age <- reqSection "age" "Age of user"
happy <- optSection' "happy" yesOrNo
"Current happiness status"
kids <- reqSection' "kids" (oneOrList kidSpec)
"All children's names"
return $
let happyText = case happy of Just True -> " and is happy"
Just False -> " and is not happy"
Nothing -> " and is private"
in name <> " is " <> Text.pack (show (age::Integer)) <>
" years old and has kids " <>
Text.intercalate ", " kids <>
happyText
kidSpec :: ValueSpec Text
kidSpec = sectionsSpec "kid" (reqSection "name" "Kid's name")
-- | Matches the 'yes' and 'no' atoms
yesOrNo :: ValueSpec Bool
yesOrNo = True <$ atomSpec "yes" <!>
False <$ atomSpec "no"
printDoc :: IO ()
printDoc = print (generateDocs exampleSpec)
-- *Example> printDoc
-- Top-level configuration file fields:
-- name: REQUIRED text
-- Full name
-- age: REQUIRED integer
-- Age of user
-- happy: `yes` or `no`
-- Current happiness status
-- kids: REQUIRED kid or list of kid
-- All children
--
-- kid
-- name: REQUIRED text
-- Kid's name
example :: Either (NonEmpty (LoadError Position)) Text
example = loadValue exampleSpec exampleValue
-- *Example> exampleVal
-- Right "Johny Appleseed is 99 years old and has kids Bob, Tom and is happy"
```
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