Ninja Generator for Curry

A small library for generating Ninja build files in Curry.

Background

Ninja is a modern, lightweight, low-level alternative to Make that encourages users to generate its build.ninja files rather than writing them by hand. The advantage of this approach is speed, simplicity and debuggability: Ninja can quickly parse the entire dependency graph without having to run through expensive shell calls/globs/etc and the user can easily see what the generated graph expands to. Additionally Ninja offers some conveniences over Make such as automatic folder creation, a nice progress line and better defaults (parallelism, immutable variables, ...). This makes it a great fit for large projects with heavily customized build setups, especially when they involve compiling multiple languages with different compilers and tools.

This Curry library came up as a byproduct from experimenting with a Ninja-based build system for use in the KiCS2 Curry compiler, mostly to see whether creating an expressive DSL for this purpose was possible.

Example

The following is an example of how a simple Ninja file can be expressed in Curry using the NinjaBuilder monad:

import Language.Ninja.Builder
import Language.Ninja.Pretty
import Language.Ninja.Types

main :: IO ()
main = writeFile "build.ninja" $ ppNinja $ execNinjaBuilder $ do
  comment "Flags"
  var $ "cflags" =. "-Wall"
  whitespace

  comment "Rules"
  rule $ (emptyRule "cc")
    { ruleCommand = Just "gcc $cflags -c $in -o $out"
    }
  whitespace

  comment "Builds"
  build $ ["foo.o"] :. ("cc", ["foo.c"])

generates

# Flags
cflags = -Wall

# Rules
rule cc
  command = gcc $cflags -c $in -o $out

# Builds
build foo.o: cc foo.c

Note: Since a transformer version of the monad is available too (NinjaBuilderT), it is easy to create a monad that supports IO (NinjaBuilderT IO) and e.g. generate build files depending on source files in a directory.