Decode the given TOML input.

Decode the given TOML input using the given Decoder.

Decode a TOML file at the given file path.

A type class containing the default Decoder for the given type.

See the docs for Decoder for examples.

A Decoder a represents a function for decoding a TOML value to a value of type a.

Generally, you'd only need to chain the getField* functions together, like

decoder =
  MyConfig
    <$> getField "a"
    <*> getField "b"
    <*> getField "c"

or use interfaces like Monad and Alternative:

decoder = do
  cfgType <- getField "type"
  case cfgType of
    "int" -> MyIntValue <$> (getField "int" <|> getField "integer")
    "bool" -> MyBoolValue <$> getField "bool"
    _ -> fail $ "Invalid type: " <> cfgType

but you can also manually implement a Decoder with makeDecoder.

Decode a field in a TOML Value. Equivalent to getFields with a single-element list.

a = 1
b = asdf

-- MyConfig 1 "asdf"
MyConfig <$> getField "a" <*> getField "b"

Decode a field in a TOML Value or succeed with a default value when the field is missing.

a = 1
# b is missing

-- MyConfig 1 "asdf"
MyConfig <$> getFieldOr 42 "a" <*> getFieldOr "asdf" "b"

Decode a nested field in a TOML Value.

a.b = 1

-- MyConfig 1
MyConfig <$> getFields ["a", "b"]

Decode a field in a TOML Value, or Nothing if the field doesn't exist. Equivalent to getFieldsOpt with a single-element list.

a = 1

-- MyConfig (Just 1) Nothing
MyConfig <$> getFieldOpt "a" <*> getFieldOpt "b"

Decode a nested field in a TOML Value, or Nothing if any of the fields don't exist.

a.b = 1

-- MyConfig (Just 1) Nothing Nothing
MyConfig
  <$> getFieldsOpt ["a", "b"]
  <*> getFieldsOpt ["a", "c"]
  <*> getFieldsOpt ["b", "c"]

Same as getField, except with the given Decoder.

Same as getFields, except with the given Decoder.

Same as getFieldOpt, except with the given Decoder.

Same as getFieldsOpt, except with the given Decoder.

Decode a list of values using the given Decoder.

[[a]]
b = 1

[[a]]
b = 2

-- MyConfig [1, 2]
MyConfig
  <$> getFieldWith (getArrayOf (getField "b")) "a"

The underlying decoding monad that either returns a value of type a or returns an error.

Manually implement a Decoder with the given function.

Run a Decoder with the given Value.

makeDecoder $ \v -> do
  a <- runDecoder decoder1 v
  b <- runDecoder decoder2 v
  return (a, b)

Satisfies

makeDecoder . runDecoder === id
runDecoder . makeDecoder === id

Throw an error indicating that the given Value is invalid.

makeDecoder $ \v ->
  case v of
    Integer 42 -> invalidValue "We don't like this number" v
    _ -> runDecoder tomlDecoder v

-- or alternatively,
tomlDecoder >>= case
  42 -> makeDecoder $ invalidValue "We don't like this number"
  v -> pure v

Throw an error indicating that the given Value isn't the correct type of value.

makeDecoder $ \v ->
  case v of
    String s -> ...
    _ -> typeMismatch v

Throw a generic failure message.

Throw the given DecodeError.