Hello world

.gitignore

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+.stack-work/
+dhall-typescript.cabal
+*~

ChangeLog.md

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+# Changelog for dhall-typescript
+
+## Unreleased changes

LICENSE

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+Copyright Frederik Hangøj Iversen (c) 2020
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Frederik Hangøj Iversen nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

README.md

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+# dhall-typescript
+
+    $ dhall-typescript <<< '< a : Integer | b : Text | c : { m : Natural } >'
+    { a: number; } | { b: string; } | { c: { m: number; }; }
+

Setup.hs

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+import Distribution.Simple
+main = defaultMain

app/Main.hs

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+module Main where
+
+import qualified Dhall.TypeScript
+
+main :: IO ()
+main = Dhall.TypeScript.main

package.yaml

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+name:                dhall-typescript
+version:             0.1.0.0
+github:              "fredefox/dhall-typescript"
+license:             BSD3
+author:              "Frederik Hangøj Iversen"
+maintainer:          "fhi.1990@gmail.com"
+copyright:           "2020 Frederik Hangøj Iversen"
+
+extra-source-files:
+- README.md
+- ChangeLog.md
+
+# Metadata used when publishing your package
+# synopsis:            Short description of your package
+# category:            Web
+
+# To avoid duplicated efforts in documentation and dealing with the
+# complications of embedding Haddock markup inside cabal files, it is
+# common to point users to the README.md file.
+description:         Please see the README on GitHub at <https://github.com/fredefox/dhall-typescript#readme>
+
+dependencies:
+  - base >= 4.7 && < 5
+  - dhall
+  - prettyprinter
+  - text
+  - containers
+
+default-extensions:
+  - ConstraintKinds
+  - DeriveGeneric
+  - FlexibleContexts
+  - FlexibleInstances
+  - GADTs
+  - GeneralizedNewtypeDeriving
+  - LambdaCase
+  - NamedWildCards
+  - OverloadedStrings
+  - ScopedTypeVariables
+  - StandaloneDeriving
+  - TupleSections
+  - TypeApplications
+  - TypeFamilies
+  - TypeSynonymInstances
+  - UnicodeSyntax
+  - ViewPatterns
+  - DerivingStrategies
+  - EmptyCase
+
+library:
+  source-dirs: src
+
+executables:
+  dhall-typescript:
+    main:                Main.hs
+    source-dirs:         app
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - dhall-typescript

src/Data/Language/TypeScript.hs

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+module Data.Language.TypeScript
+  ( Statement(..)
+  , Type(..)
+  , Name(..)
+  , TypeDeclaration(..)
+  , Primitive(..)
+  , Object(..)
+  , Union(..)
+  ) where
+{-# OPTIONS_GHC -Wall #-}
+
+import Data.Text (Text)
+import Data.Text.Prettyprint.Doc
+import Data.Map (Map)
+import qualified Data.Map as Map
+import Data.List
+
+deriving stock instance Show Name
+newtype Name = Name Text
+
+deriving stock instance Show Statement
+data Statement = StatementTypeDeclaration TypeDeclaration
+
+instance Pretty Name where
+  pretty (Name nm) = pretty nm
+
+data TypeDeclaration = TypeDeclaration Name Type
+deriving stock instance Show TypeDeclaration
+instance Pretty TypeDeclaration where
+  pretty = error "TODO"
+
+data Primitive = TsText | TsInteger
+deriving stock instance Show Primitive
+instance Pretty Primitive where
+  pretty = \case
+    TsText -> "string"
+    TsInteger -> "number"
+
+newtype Object = Object (Map Text Type)
+deriving stock instance Show Object
+instance Pretty Object where
+  pretty (Object m) = vsep $ ["{", nest 2 (vsep docs), "}"]
+    where
+    docs = decl <$> Map.toList m
+    decl :: (Text, Type) -> Doc ann
+    decl (txt, tp) = pretty txt <> ":" <+> pretty tp <> ";"
+
+newtype Union = Union ([] Type)
+
+deriving stock instance Show Union
+instance Pretty Union where
+  pretty (Union tps) = sepBy "|" $ pretty <$> tps
+
+sepBy :: Doc a -> [Doc a] -> Doc a
+sepBy x = sep . intersperse x
+
+data Type = Primitive Primitive | TypeObject Object | TypeUnion Union | Array Type | TypeNamed Name
+deriving stock instance Show Type
+instance Pretty Type where
+  pretty = \case
+    Primitive p  -> pretty p
+    TypeObject o -> pretty o
+    TypeUnion u  -> pretty u
+    Array a      -> pretty a
+    TypeNamed n  -> pretty n
+

src/Dhall/TypeScript.hs

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+module Dhall.TypeScript (main) where
+{-# OPTIONS_GHC -Wall #-}
+
+import qualified Dhall.Core as Dhall
+import qualified Dhall.Parser
+import Data.Maybe (fromMaybe)
+import qualified Data.Text.IO as Text
+import qualified Data.Language.TypeScript as TypeScript
+import qualified Data.Text.Prettyprint.Doc as Pretty
+import qualified Data.Text.Prettyprint.Doc.Render.Text as Pretty
+import qualified Data.Map as Map
+import Data.Text (Text)
+import qualified Dhall.Map as Dhall
+import Control.Monad
+
+main :: IO ()
+main = do
+  txt <- Text.getContents
+  e <- Dhall.throws (Dhall.Parser.exprFromText (fromMaybe "(stdin)" mFilePath) txt)
+  case fromDhall e of
+    Nothing -> Text.putStrLn "Could not convert expression"
+    Just expr -> Pretty.putDoc $ Pretty.pretty expr <> "\n"
+
+fromDhall :: Show a => Show b => Dhall.Expr a b -> Maybe TypeScript.Type
+fromDhall e = case e of
+  Dhall.Annot{}            -> err
+  Dhall.App{}              -> err
+  Dhall.Assert{}           -> err
+  Dhall.BoolAnd{}          -> err
+  Dhall.BoolEQ{}           -> err
+  Dhall.BoolIf{}           -> err
+  Dhall.BoolLit{}          -> err
+  Dhall.BoolNE{}           -> err
+  Dhall.BoolOr{}           -> err
+  Dhall.Bool{}             -> err
+  Dhall.CombineTypes{}     -> err
+  Dhall.Combine{}          -> err
+  Dhall.Const{}            -> err
+  Dhall.DoubleLit{}        -> err
+  Dhall.DoubleShow{}       -> err
+  Dhall.Double{}           -> err
+  Dhall.Embed{}            -> err
+  Dhall.Equivalent{}       -> err
+  Dhall.Field{}            -> err
+  Dhall.ImportAlt{}        -> err
+  Dhall.IntegerClamp{}     -> err
+  Dhall.IntegerLit{}       -> err
+  Dhall.IntegerNegate{}    -> err
+  Dhall.IntegerShow{}      -> err
+  Dhall.IntegerToDouble{}  -> err
+  Dhall.Integer{}          -> pure (TypeScript.Primitive TypeScript.TsInteger)
+  Dhall.Lam{}              -> err
+  Dhall.Let{}              -> err
+  Dhall.ListAppend{}       -> err
+  Dhall.ListBuild{}        -> err
+  Dhall.ListFold{}         -> err
+  Dhall.ListHead{}         -> err
+  Dhall.ListIndexed{}      -> err
+  Dhall.ListLast{}         -> err
+  Dhall.ListLength{}       -> err
+  Dhall.ListLit{}          -> err
+  Dhall.ListReverse{}      -> err
+  Dhall.List{}             -> err
+  Dhall.Merge{}            -> err
+  Dhall.NaturalBuild{}     -> err
+  Dhall.NaturalEven{}      -> err
+  Dhall.NaturalFold{}      -> err
+  Dhall.NaturalIsZero{}    -> err
+  Dhall.NaturalLit{}       -> err
+  Dhall.NaturalOdd{}       -> err
+  Dhall.NaturalPlus{}      -> err
+  Dhall.NaturalShow{}      -> err
+  Dhall.NaturalSubtract{}  -> err
+  Dhall.NaturalTimes{}     -> err
+  Dhall.NaturalToInteger{} -> err
+  Dhall.Natural{}          -> pure (TypeScript.Primitive TypeScript.TsInteger)
+  Dhall.None{}             -> err
+  Dhall.Note _ e0          -> fromDhall e0
+  Dhall.OptionalBuild{}    -> err
+  Dhall.OptionalFold{}     -> err
+  Dhall.Optional{}         -> err
+  Dhall.Pi{}               -> err
+  Dhall.Prefer{}           -> err
+  Dhall.Project{}          -> err
+  Dhall.RecordCompletion{} -> err
+  Dhall.RecordLit{}        -> err
+  Dhall.Record r           -> TypeScript.TypeObject <$> fromDhall_Object r
+  Dhall.Some{}             -> err
+  Dhall.TextAppend{}       -> err
+  Dhall.TextLit{}          -> err
+  Dhall.TextShow{}         -> err
+  Dhall.Text               -> pure $ TypeScript.Primitive TypeScript.TsText
+  Dhall.ToMap{}            -> err
+  Dhall.Union u            -> TypeScript.TypeUnion <$> fromDhall_Union u
+  Dhall.Var v              -> fromDhall_Named v
+  where
+  err = error $ show e
+
+fromDhall_Union :: forall a b . Show a => Show b => Dhall.Map Text (Maybe (Dhall.Expr a b)) -> Maybe TypeScript.Union
+-- TODO: Maybe Map.fromList + Dhall.toList is a bit silly here.
+fromDhall_Union
+  =   traverse go . Dhall.toList
+  >=> fmap TypeScript.Union . traverse unionand
+  where
+  -- TODO: Dunno what it means when a dhall union has a Nothing as an entry.
+  go :: (Text, Maybe (Dhall.Expr a b)) -> Maybe (Text, Dhall.Expr a b)
+  go (_, Nothing) = Nothing
+  go (t, Just x)  = pure $ (t, x)
+  -- Will fail if `expr` fails to translate.
+  unionand :: (Text, Dhall.Expr a b) -> Maybe TypeScript.Type
+  -- unionand (txt, expr) = (txt,) <$> fromDhall expr
+  unionand (txt, expr) = (\x -> TypeScript.TypeObject $ TypeScript.Object $ Map.singleton txt x) <$> fromDhall expr
+
+-- TODO: Maybe Map.fromList + Dhall.toList is a bit silly here.
+fromDhall_Object :: Show a => Show b => Dhall.Map Text (Dhall.Expr a b) -> Maybe TypeScript.Object
+fromDhall_Object = fmap (TypeScript.Object . Map.fromList) . traverse @_ @Maybe go . Dhall.toList
+  where
+  go (txt, expr) = (txt,) <$> fromDhall expr
+
+fromDhall_Named :: Dhall.Var -> Maybe TypeScript.Type
+fromDhall_Named (Dhall.V nm _) = pure $ TypeScript.TypeNamed $ TypeScript.Name nm
+
+mFilePath :: Maybe FilePath
+mFilePath = Nothing

stack.yaml

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+# This file was automatically generated by 'stack init'
+#
+# Some commonly used options have been documented as comments in this file.
+# For advanced use and comprehensive documentation of the format, please see:
+# https://docs.haskellstack.org/en/stable/yaml_configuration/
+
+# Resolver to choose a 'specific' stackage snapshot or a compiler version.
+# A snapshot resolver dictates the compiler version and the set of packages
+# to be used for project dependencies. For example:
+#
+# resolver: lts-3.5
+# resolver: nightly-2015-09-21
+# resolver: ghc-7.10.2
+#
+# The location of a snapshot can be provided as a file or url. Stack assumes
+# a snapshot provided as a file might change, whereas a url resource does not.
+#
+# resolver: ./custom-snapshot.yaml
+# resolver: https://example.com/snapshots/2018-01-01.yaml
+resolver: lts-15.0
+
+# User packages to be built.
+# Various formats can be used as shown in the example below.
+#
+# packages:
+# - some-directory
+# - https://example.com/foo/bar/baz-0.0.2.tar.gz
+#   subdirs:
+#   - auto-update
+#   - wai
+packages:
+- .
+# Dependency packages to be pulled from upstream that are not in the resolver.
+# These entries can reference officially published versions as well as
+# forks / in-progress versions pinned to a git hash. For example:
+#
+# extra-deps:
+# - acme-missiles-0.3
+# - git: https://github.com/commercialhaskell/stack.git
+#   commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
+#
+# extra-deps: []
+
+# Override default flag values for local packages and extra-deps
+# flags: {}
+
+# Extra package databases containing global packages
+# extra-package-dbs: []
+
+# Control whether we use the GHC we find on the path
+# system-ghc: true
+#
+# Require a specific version of stack, using version ranges
+# require-stack-version: -any # Default
+# require-stack-version: ">=2.1"
+#
+# Override the architecture used by stack, especially useful on Windows
+# arch: i386
+# arch: x86_64
+#
+# Extra directories used by stack for building
+# extra-include-dirs: [/path/to/dir]
+# extra-lib-dirs: [/path/to/dir]
+#
+# Allow a newer minor version of GHC than the snapshot specifies
+# compiler-check: newer-minor

stack.yaml.lock

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+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/lock_files
+
+packages: []
+snapshots:
+- completed:
+    size: 488576
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/15/0.yaml
+    sha256: e4b6a87b47ec1cf63a7f1a0884a3b276fce2b0d174a10e8753c4f618e7983568
+  original: lts-15.0

test/Spec.hs

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+main :: IO ()
+main = putStrLn "Test suite not yet implemented"