Migrate dhall-{bash,json,text} into this repository (#661)

The motivation for this change is:

* To catch build failures in downstream packages whenever we make a breaking
  change to the `dhall` API
* To reduce the amount of work I need in order to cut a release for all of
  these packages
* To better share Nix/CI-related logic between the projects

Note that I have not yet migrated `dhall-nix` in.  I'm waiting for
dhall-lang/dhall-nix#17 to be fixed since
`dhall-nix` is incompatible with later versions of `megaparsec` due to
`hnix`.

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2017 Gabriel Gonzalez
+Copyright (c) 2018 Gabriel Gonzalez
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without

README.md

@@ -1,142 +1,25 @@
-# `dhall 1.18.0`
+# `dhall-haskell`
 
-Dhall is a programmable configuration language that is not Turing-complete
+This repository is a shared repository for all of the `dhall-*` Haskell
+packages, including:
 
-You can think of Dhall as: JSON + functions + types + imports
+* [`dhall`](./dhall)
+* [`dhall-bash`](./dhall-bash)
+* [`dhall-json`](./dhall-json)
+* [`dhall-text`](./dhall-text)
 
-You will probably want to read the language-agnostic README here:
+Navigate to each package's directory for their respective `README`s
 
-* [`dhall-lang` `README`](https://github.com/dhall-lang/dhall-lang/blob/master/README.md)
+# Quick start
 
-This repository (and this `README`) focuses on the Haskell implementation of
-Dhall
+You can build all of the packages by running:
 
-## Motivation
-
-*"Why not configure my program using JSON or YAML?"*
-
-JSON or YAML are suitable for small configuration files, but larger
-configuration files with complex schemas require programming language features
-to reduce repetition.  Otherwise, the repetitive configuration files become
-error-prone and difficult to maintain/migrate.
-
-This post explains in more detail the motivation behind programmable
-configuration files:
-
-* [Programmable configuration files](https://github.com/dhall-lang/dhall-lang/wiki/Programmable-configuration-files)
-
-*"Why not configure my program using Haskell code?"*
-
-You probably don't want to rebuild your program every time you make a
-configuration change.  Recompilation is slow and requires the GHC toolchain
-to be installed anywhere you want to make configuration changes.
-
-## Quick start
-
-Given this Haskell program saved to `example.hs`:
-
-```haskell
--- example.hs
-
-{-# LANGUAGE DeriveGeneric     #-}
-{-# LANGUAGE OverloadedStrings #-}
-
-import Dhall
-
-data Example = Example { foo :: Integer, bar :: Vector Double }
-    deriving (Generic, Show)
-
-instance Interpret Example
-
-main :: IO ()
-main = do
-    x <- input auto "./config"
-    print (x :: Example)
-```
-
-... which reads in this configuration file:
-
-```bash
-$ cat ./config
-{ foo = 1
-, bar = ./bar
-}
-```
-
-... which in turn references this other file:
-
-```
-$ cat ./bar
-[3.0, 4.0, 5.0]
 ```
-
-... you can interpret the Haskell program like this:
-
-```bash
-$ nix-shell nix/test-dhall.nix
-[nix-shell]$ runghc example.hs
-Example {foo = 1, bar = [3.0,4.0,5.0]}
-```
-
-You can also interpret Dhall programs directly using the installed command-line
-compiler:
-
-```bash
-$ dhall
-List/head Double ./bar
-<Ctrl-D>
-Optional Double
-
-Some 3.0
-```
-
-... and you can reference remote expressions or functions by their URL, too:
-
-```bash
-$ dhall
-let null = https://raw.githubusercontent.com/dhall-lang/Prelude/35deff0d41f2bf86c42089c6ca16665537f54d75/List/null
-in  null Double ./bar
-<Ctrl-D>
-Bool
-
-False
-```
-
-Now go read the
-[Dhall tutorial](https://hackage.haskell.org/package/dhall/docs/Dhall-Tutorial.html)
-to learn more
-
-## Building this project
-
-Nix + Cabal is the recommended workflow for project development since continuous
-integration uses Nix to build and test the project.  Other development tools and
-workflows are also supported on a best-effort basis.
-
-You can build the project using only Nix by running this command from the root
-of the repository:
-
-```bash
 $ nix-build
 ```
 
-More commonly, you will want to incrementally build the project using `cabal`.
-You can either do so inside of a `nix-shell`:
-
-```bash
-$ nix-shell
-[nix-shell]$ cabal configure
-[nix-shell]$ cabal build
-[nix-shell]$ cabal test
-```
-
-... or you can add `nix: True` to your `~/.cabal/config` file and then you can
-run the same `cabal` commands without an explicit `nix-shell`:
-
-```bash
-$ cabal configure
-$ cabal build
-$ cabal test
-```
+... or you can run `nix-build` within each package's respective directory to
+build just that one package.
 
 ## Development status
 

default.nix

@@ -1 +1,5 @@
-(import ./shared.nix {}).dhall
+let
+  shared = import ./nix/shared.nix {};
+
+in
+  { inherit (shared) dhall dhall-bash dhall-json dhall-text; }

dhall-bash/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2018 Gabriel Gonzalez
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.
+
+2. 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.
+
+3. Neither the name of the author nor the names of its 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 HOLDER 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.

dhall-bash/README.md

@@ -0,0 +1,34 @@
+# `dhall-bash 1.0.16`
+
+[![Hackage](https://img.shields.io/hackage/v/dhall-bash.svg)](https://hackage.haskell.org/package/dhall-bash)
+
+This `dhall-bash` package provides a Dhall to Bash compiler so that you can
+easily marshall Dhall values into your Bash scripts
+
+This does not compile all available Dhall language constructs into Bash and
+only supports extracting primitive values, lists, optional values and records
+from normalized expressions.
+
+## Quick start
+
+If you have Nix installed, then you can build and install this package using:
+
+```bash
+$ nix-env --install --file default.nix
+$ dhall-to-bash <<< '1'
+1
+$ dhall-to-bash <<< '"ABC" ++ "DEF"'
+ABCDEF
+$ dhall-to-bash --declare FOO <<< '"ABC" ++ "DEF"'
+declare -r FOO=ABCDEF
+$ eval $(dhall-to-bash --declare FOO <<< '"ABC" ++ "DEF"')
+$ echo "${FOO}"
+ABCDEF
+$ dhall-to-bash --declare BAR
+let replicate = https://ipfs.io/ipfs/QmcTbCdS21pCxXysTzEiucDuwwLWbLUWNSKwkJVfwpy2zK/Prelude/List/replicate
+in  replicate +10 Integer 1
+<Ctrl-D>
+declare -r -a BAR=(1 1 1 1 1 1 1 1 1 1)
+$ dhall-to-bash --declare BAZ <<< '{ qux = 1, xyzzy = True }'
+declare -r -A BAZ=([qux]=1 [xyzzy]=true)
+```

dhall-bash/default.nix

@@ -0,0 +1 @@
+(import ../nix/shared.nix {}).dhall-bash

dhall-bash/dhall-bash.cabal

@@ -0,0 +1,51 @@
+Name: dhall-bash
+Version: 1.0.16
+Cabal-Version: >=1.8.0.2
+Build-Type: Simple
+Tested-With: GHC == 7.10.2, GHC == 8.0.1
+License: BSD3
+License-File: LICENSE
+Copyright: 2017 Gabriel Gonzalez
+Author: Gabriel Gonzalez
+Maintainer: Gabriel439@gmail.com
+Bug-Reports: https://github.com/dhall-lang/dhall-haskell/issues
+Synopsis: Compile Dhall to Bash
+Description:
+    Use this package if you want to compile Dhall expressions to Bash.
+    You can use this package as a library or an executable:
+    .
+    * See the "Dhall.Bash" module if you want to use this package as a library
+    .
+    * Use the @dhall-to-bash@ if you want an executable
+    .
+    The "Dhall.Bash" module also contains instructions for how to use this
+    package
+Category: Compiler
+Source-Repository head
+    Type: git
+    Location: https://github.com/dhall-lang/dhall-haskell/tree/master/dhall-bash
+
+Library
+    Hs-Source-Dirs: src
+    Build-Depends:
+        base                      >= 4.8.0.0 && < 5   ,
+        bytestring                              < 0.11,
+        containers                              < 0.6 ,
+        dhall                     >= 1.18.0  && < 1.19,
+        neat-interpolation                      < 0.4 ,
+        shell-escape                            < 0.3 ,
+        text                      >= 0.2     && < 1.3
+    Exposed-Modules: Dhall.Bash
+    GHC-Options: -Wall
+
+Executable dhall-to-bash
+    Hs-Source-Dirs: exec
+    Main-Is: Main.hs
+    Build-Depends:
+        base                                  ,
+        bytestring                            ,
+        dhall                                 ,
+        dhall-bash                            ,
+        optparse-generic >= 1.1.1    && < 1.4 ,
+        text
+    GHC-Options: -Wall

dhall-bash/exec/Main.hs

@@ -0,0 +1,73 @@
+{-# LANGUAGE DataKinds         #-}
+{-# LANGUAGE DeriveAnyClass    #-}
+{-# LANGUAGE DeriveGeneric     #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE RecordWildCards   #-}
+{-# LANGUAGE TypeOperators     #-}
+
+module Main where
+
+import Control.Exception (SomeException)
+import Data.ByteString (ByteString)
+import Options.Generic (Generic, ParseRecord, type (<?>)(..))
+import System.Exit (ExitCode(..))
+
+import qualified Control.Exception
+import qualified Data.ByteString
+import qualified Data.Text.IO
+import qualified Dhall
+import qualified Dhall.Bash
+import qualified Dhall.Import
+import qualified Dhall.Parser
+import qualified Dhall.TypeCheck
+import qualified GHC.IO.Encoding
+import qualified Options.Generic
+import qualified System.Exit
+import qualified System.IO
+
+data Options = Options
+    { explain :: Bool
+        <?> "Explain error messages in detail"
+    , declare :: Maybe ByteString
+        <?> "Declare the given variable as a statement instead of an expression"
+    } deriving (Generic, ParseRecord)
+
+main :: IO ()
+main = do
+    GHC.IO.Encoding.setLocaleEncoding GHC.IO.Encoding.utf8
+    Options {..} <- Options.Generic.getRecord "Compile Dhall to Bash"
+
+    (if unHelpful explain then Dhall.detailed else id) (handle (do
+        inText <- Data.Text.IO.getContents
+
+        expr <- case Dhall.Parser.exprFromText "(stdin)" inText of
+            Left  err  -> Control.Exception.throwIO err
+            Right expr -> return expr
+
+        expr' <- Dhall.Import.load expr
+        case Dhall.TypeCheck.typeOf expr' of
+            Left  err -> Control.Exception.throwIO err
+            Right _   -> return ()
+
+        bytes <- case unHelpful declare of
+            Nothing  -> do
+                case Dhall.Bash.dhallToExpression expr' of
+                    Left  err   -> Control.Exception.throwIO err
+                    Right bytes -> return bytes
+            Just var -> do
+                case Dhall.Bash.dhallToStatement expr' var of
+                    Left  err   -> Control.Exception.throwIO err
+                    Right bytes -> return bytes
+        Data.ByteString.putStr bytes ))
+
+handle :: IO a -> IO a
+handle = Control.Exception.handle handler
+  where
+    handler :: SomeException -> IO a
+    handler e = case Control.Exception.fromException e of
+        Just ExitSuccess -> do
+            Control.Exception.throwIO e
+        _ -> do
+            System.IO.hPutStrLn System.IO.stderr ""
+            System.IO.hPrint    System.IO.stderr e
+            System.Exit.exitFailure

dhall-bash/shell.nix

@@ -0,0 +1 @@
+(import ../nix/shared.nix {}).shell-dhall-bash