Overhaul the config system with Lua

[Walt Ford]

On Sat, Mar 15, 2014 at 01:11:03AM +0800, 朱江 wrote:
> I want to overhaul the config system with Lua, and it will be my GSoC 2014
> project. Here is the
> proposal<https://docs.google.com/document/d/1azZm8WHBiT_oaQ1fEhUWGiYWyn4hvwxEkMXqf1aR00g/edit?usp=sharing>

That's an excellent project.  I've had Lua in my own base system for
years and have converted the rc system to use it at various times,
along with some base utilities.  I've been considering posting a
Kickstarter project to finally finish it all, but Lua isn't the most
popular language, and FreeBSD isn't the most popular OS.

The main goal of my work was to present a more uniform userland.
Everybody hacks on the kernel, but userland gets a little ignored.
There's not much uniformity between command-line options, interactivity,
color, scriptability, layout, and naming of utilities, and Lua was a great
fit to clean it up.

I even got it to the point of generating utilities on its own.  When
Robert Watson imported audit(2) it was able to crawl the headers and
generate a utility in the style of top(1) that showed the most active
audit record types as colorized output like gstat(8).  Lua could get to
the point where it automatically generates entire applications with
uniform command-line options, interactivity, color, and scriptability, just
based on kernel subsystem definitions in header files plus a little glue.

Unfortunately, I've never had the time or money to finish it all.  That
audit utility is dated 2007.

> I will create a wiki in my site soon. Please let me know if you have any
> good ideas about the new config system. They will not be a part of my GSoC
> project, however, I will do this work continuously after GSoC.

I converted a lot of FreeBSD to Lua, but never config(8).  Some build issues
to figure out how to solve are:

	* the differences and sloppiness in how userland and kernel options
	  are handled
		kernel options are manually documented in sys/conf/options*
		    and have no man page
		share/examples/etc/kern.conf doesn't exist
		userland options are documented in tools/build/options and
		    the man page, src.conf, is generated using a shell script
		share/examples/etc/src.conf doesn't exist
		share/examples/etc/make.conf is manually updated and often
		    out-of-date

	* generate GENERIC config files
		currently things are copied and pasted for every arch
		would need to account for DEFAULTS

	* automatic generation of OptionalObsoleteFiles.inc
		must be manually updated and has never been complete
		a make target could build twice with and without option then
		    find the missing files
		probably a better job for jenkins and make, but Lua could
		    help

I'm sure there are other ways to improve the build system as a whole using
Lua, as long as you don't confine yourself to reimplementing config(8)
only.  The information about options currently stored in tools/build/options
and sys/conf/options should really be part of config(8), along with the
architecture information necessary to generate documentation or source files
automatically.

Lua would make a great kernel language as well, another one of the projects
I started and haven't had time to play with.

-- 
Walt