How do I write a waf file for a custom compiler?

Question

I got sick of looking up the magic symbols in make and decided to try waf.

I'm trying to use calibre to make ebooks and I'd like to create a wscript that takes in a file, runs a program with some arguments that include that file, and produces an output. Waf should only build if the input file is newer than the output.

In make, I'd write a makefile like this:

%.epub: %.recipe
    ebook-convert $ .epub --test -vv --debug-pipeline debug

Where % is a magic symbol for the basename of the file and $ a symbol for the output filename (basename.epub).

I could call make soverflow.epub and it would run ebook-convert on soverflow.recipe. If the .recipe hadn't changed since the last build, it wouldn't do anything.

How can I do something similar in waf?

(Why waf? Because it uses a real language that I already know. If this is really easy to use in scons, that's a good answer too.)

Answer 1

I figured out how to make a basic wscript file, but I don't know how to build targets specified on the command-line.

---

The Waf Book has a section on Task generators. The Name and extension-based file processing section gives an example for lua that I adapted:

from waflib import TaskGen
TaskGen.declare_chain(
        rule         = 'ebook-convert ${SRC} .epub --test -vv --debug-pipeline debug', 
        ext_in       = '.recipe', 
        ext_out      = '.epub'
)

top = '.'
out = 'build'

def configure(conf):
        pass

def build(bld):
    bld(source='soverflow.recipe')

It even automatically provides a clean step that removes the epub.

Answer 2

I gave up on waf for a bit and found that it's pretty easy to do in scons. The documentation has a section on Writing Your Own Builders.

# Setup the custom builder
def add_book_builder(env):
    rule = 'ebook-convert $SOURCE .epub --test -vv --debug-pipeline debug'
    bld = Builder(action = rule,
                  suffix = '.epub',
                  src_suffix = '.recipe')
    env.Append(BUILDERS = {'Book' : bld})

env = Environment()
add_book_builder(env)

# Define the epubs that can be built
for target in Glob('*.recipe'):
    env.Book(target)

Running scons soverflow.epub builds the epub. I can add Default(env.Book('soverflow.recipe')) to the end to build it when there are no arguments.

Unlike waf, it doesn't provide a clean step. Instead, you can clean with scons -c.