| Copyright | © Herbert Valerio Riedel 2015-2018 |
|---|---|
| Safe Haskell | Safe |
| Language | Haskell2010 |
Data.YAML
Contents
Description
SPDX-License-Identifier: GPL-3.0
Document oriented YAML parsing API inspired by aeson.
Overview
The diagram below depicts the standard layers of a YAML 1.2 processor. This module covers the upper Native and Representation layers, whereas the Data.YAML.Event and Data.YAML.Token modules provide access to the lower Serialization and Presentation layers respectively.
Quick Start Tutorial
Let's assume we want to decode (i.e. load) a simple YAML document
- name: Erik Weisz age: 52 magic: True - name: Mina Crandon age: 53
into a native Haskell data structure of type [Person], i.e. a list of Person records.
The code below shows how to manually define a Person record type together with a FromYAML instance:
{-# LANGUAGE OverloadedStrings #-}
import Data.YAML
data Person = Person
{ name :: Text
, age :: Int
, magic :: Bool
} deriving Show
instance FromYAML Person where
parseYAML = withMap "Person" $ \m -> Person
<$> m .: "name"
<*> m .: "age"
<*> m .:? "magic" .!= FalseAnd now we can decode the YAML document like so:
>>>decode "- name: Erik Weisz\n age: 52\n magic: True\n- name: Mina Crandon\n age: 53" :: Either String [[Person]]Right [[Person {name = "Erik Weisz", age = 52, magic = True},Person {name = "Mina Crandon", age = 53, magic = False}]]
- decode :: FromYAML v => ByteString -> Either String [v]
- decodeStrict :: FromYAML v => ByteString -> Either String [v]
- class FromYAML a where
- data Parser a
- parseEither :: Parser a -> Either String a
- typeMismatch :: String -> Node -> Parser a
- type Mapping = Map Node Node
- (.:) :: FromYAML a => Mapping -> Text -> Parser a
- (.:?) :: FromYAML a => Mapping -> Text -> Parser (Maybe a)
- (.:!) :: FromYAML a => Mapping -> Text -> Parser (Maybe a)
- (.!=) :: Parser (Maybe a) -> a -> Parser a
- withSeq :: String -> ([Node] -> Parser a) -> Node -> Parser a
- withBool :: String -> (Bool -> Parser a) -> Node -> Parser a
- withFloat :: String -> (Double -> Parser a) -> Node -> Parser a
- withInt :: String -> (Integer -> Parser a) -> Node -> Parser a
- withNull :: String -> Parser a -> Node -> Parser a
- withStr :: String -> (Text -> Parser a) -> Node -> Parser a
- withMap :: String -> (Mapping -> Parser a) -> Node -> Parser a
- decodeNode :: ByteString -> Either String [Doc Node]
- decodeNode' :: SchemaResolver -> Bool -> Bool -> ByteString -> Either String [Doc Node]
- newtype Doc n = Doc n
- data Node
- data Scalar
- data SchemaResolver = SchemaResolver {}
- failsafeSchemaResolver :: SchemaResolver
- jsonSchemaResolver :: SchemaResolver
- coreSchemaResolver :: SchemaResolver
- decodeLoader :: forall n m. MonadFix m => Loader m n -> ByteString -> m (Either String [n])
- data Loader m n = Loader {}
- type NodeId = Word
Typeclass-based resolving/decoding
decode :: FromYAML v => ByteString -> Either String [v] Source #
Decode YAML document(s) using the YAML 1.2 Core schema
Each document contained in the YAML stream produce one element of the response list. Here's an example of decoding two concatenated YAML documents:
>>>decode "Foo\n---\nBar" :: Either String [Text]Right ["Foo","Bar"]
Note that an empty stream doesn't contain any (non-comment) document nodes, and therefore results in an empty result list:
>>>decode "# just a comment" :: Either String [Text]Right []
decode uses the same settings as decodeNode for tag-resolving. If
you need a different custom parsing configuration, you need to
combine parseEither and decodeNode' yourself.
decodeStrict :: FromYAML v => ByteString -> Either String [v] Source #
Like decode but takes a strict ByteString
Since: 0.1.1.0
class FromYAML a where Source #
A type into which YAML nodes can be converted/deserialized
Minimal complete definition
Instances
YAML Parser Monad used by FromYAML
See also parseEither or decode
parseEither :: Parser a -> Either String a Source #
Run Parser
A common use-case is parseEither parseYAML.
Informative failure helper
This is typically used in fall-through cases of parseYAML like so
instance FromYAML ... where parseYAML ... = ... parseYAML node = typeMismatch "SomeThing" node
Since: 0.1.1.0
Accessors for YAML Mappings
Prism-style parsers
withSeq :: String -> ([Node] -> Parser a) -> Node -> Parser a Source #
Operate on tag:yaml.org,2002:seq node (or fail)
withBool :: String -> (Bool -> Parser a) -> Node -> Parser a Source #
Operate on tag:yaml.org,2002:bool node (or fail)
withFloat :: String -> (Double -> Parser a) -> Node -> Parser a Source #
Operate on tag:yaml.org,2002:float node (or fail)
withInt :: String -> (Integer -> Parser a) -> Node -> Parser a Source #
Operate on tag:yaml.org,2002:int node (or fail)
withNull :: String -> Parser a -> Node -> Parser a Source #
Operate on tag:yaml.org,2002:null node (or fail)
withStr :: String -> (Text -> Parser a) -> Node -> Parser a Source #
Operate on tag:yaml.org,2002:str node (or fail)
withMap :: String -> (Mapping -> Parser a) -> Node -> Parser a Source #
Operate on tag:yaml.org,2002:seq node (or fail)
"Concrete" AST
decodeNode :: ByteString -> Either String [Doc Node] Source #
Parse and decode YAML document(s) into Node graphs
This is a convenience wrapper over decodeNode'
decodeNode = decodeNode' coreSchemaResolver False False
In other words,
- Use the YAML 1.2 Core schema for resolving
- Don't create
Anchornodes - Disallow cyclic anchor references
Arguments
| :: SchemaResolver | YAML Schema resolver to use |
| -> Bool | Whether to emit anchor nodes |
| -> Bool | Whether to allow cyclic references |
| -> ByteString | YAML document to parse |
| -> Either String [Doc Node] |
Customizable variant of decodeNode
YAML Document tree/graph
Constructors
| Doc n |
YAML Document node
Primitive scalar types as defined in YAML 1.2
YAML 1.2 Schema resolvers
data SchemaResolver Source #
Definition of a YAML 1.2 Schema
A YAML schema defines how implicit tags are resolved to concrete tags and how data is represented textually in YAML.
Constructors
| SchemaResolver | |
failsafeSchemaResolver :: SchemaResolver Source #
"Failsafe" schema resolver as specified in YAML 1.2 / 10.1.2. Tag Resolution
jsonSchemaResolver :: SchemaResolver Source #
Strict JSON schema resolver as specified in YAML 1.2 / 10.2.2. Tag Resolution
coreSchemaResolver :: SchemaResolver Source #
Core JSON schema resolver as specified in YAML 1.2 / 10.3.2. Tag Resolution
Generalised AST construction
decodeLoader :: forall n m. MonadFix m => Loader m n -> ByteString -> m (Either String [n]) Source #
Generalised document tree/graph construction
This doesn't yet perform any tag resolution (thus all scalars are
represented as Text values). See also decodeNode for a more
convenient interface.
Structure defining how to construct a document tree/graph