Dhall.TomlToDhall

This module exports the tomlToDhall function for translating a TOML syntax tree from tomland to a Dhall syntax tree. For now, this package does not have type inference so a Dhall type is needed.

For converting source code into a Dhall syntax tree see the dhall package, and for converting the TOML syntax tree to source code see the tomland package.

This module also exports tomlToDhallMain which implements the toml-to-dhall command which converts TOML source directly into Dhall source.

In theory all TOML objects should be converted but there are some known failure cases: * Arrays of arrays of objects - not supported by tomland * Arrays of heterogeneous primitive types - not supported by tomland * Arrays of objects of different types are allowed (note that this requires conversion to a Dhall union)

TOML bools translate to Dhall Bools:

$ cat schema.dhall
{ b : Bool }
$ toml-to-dhall schema.dhall <<< 'b = true'
{ b = True }

TOML numbers translate to Dhall numbers:

$ cat schema.dhall
{ n : Natural, d : Double }
$ toml-to-dhall schema.dhall << EOF
n = 1
d = 3.14
EOF
{ d = 3.14, n = 1}

TOML text translates to Dhall Text:

$ cat schema.dhall
{ t : Text }
$ toml-to-dhall schema.dhall << EOF
t = "Hello!"
EOF
{ t = "Hello!" }

TOML arrays and table arrays translate to Dhall List:

$ cat schema.dhall
{ nums : List Natural, tables : List { a : Natural, b : Text } }
$ toml-to-dhall schema.dhall << EOF
nums = [1, 2, 3]

[[tables]]
a = 1
b = "Hello,"
[[tables]]
a = 2
b = " World!"
EOF
{ nums = [ 1, 2, 3 ]
, tables = [ { a = 1, b = "Hello," }, { a = 2, b = " World!" } ]
}

Note, lists of lists of objects and heterogeneous lists are not supported by tomland so a paraser error will be returned:

$ cat schema.dhall
{ list : List (<a : Natural | b : Bool>) }
$ toml-to-dhall schema.dhall << EOF
list = [1, true]
EOF
toml-to-dhall: invalid TOML:
1:12:
  |
1 | list = [1, true]
  |            ^
unexpected 't'
expecting ',', ']', or integer

Because of this, unions have limited use in lists, but can be used fully in tables:

$ cat schema.dhall
{ list : List (<a : Natural | b : Bool>), item : <a : Natural | b : Bool> }
$ toml-to-dhall schema.dhall << EOF
list = [1, 2]
item = true
EOF
{ item = < a : Natural | b : Bool >.b True
, list = [ < a : Natural | b : Bool >.a 1, < a : Natural | b : Bool >.a 2 ]
}

TOML tables translate to Dhall records:

$ cat schema.dhall
{ num : Natural, table : { num1 : Natural, table1 : { num2 : Natural } } }
$ toml-to-dhall schema.dhall << EOF
num = 0

[table]
num1 = 1

[table.table1]
num2 = 2
EOF
{ num = 0, table = { num1 = 1, table1.num2 = 2 } }

Documentation

tomlToDhall :: Expr Src Void -> TOML -> Either CompileError (Expr Src Void)

tomlToDhallMain :: IO ()

data CompileError

Instances

Exception CompileError

Defined in Dhall.TomlToDhall

Methods

toException :: CompileError -> SomeException

fromException :: SomeException -> Maybe CompileError

displayException :: CompileError -> String

Show CompileError

Defined in Dhall.TomlToDhall

Methods

showsPrec :: Int -> CompileError -> ShowS

show :: CompileError -> String

showList :: [CompileError] -> ShowS