Wednesday, June 26, 2013

I'm sick of tools

Synonym's for "tool" include "framework" and "system". So for example "build tool", "build system", "web framework", "message-passing system", "text processing system", "dependency injection framework" etc.

The problem with a tool is that it takes control away from the client code. make ("Make is a tool", begins the intro) will plan your build from start to finish [1]; sphinx (also a self-described tool) starts in control and relinquishes it through plugins; maven takes usurping control to a whole new level.

I am not bashing the merits of these programs; Sphinx produces beautiful output and there simply isn't a substitute for Maven right now. I am rather noting that to the extent that these programs are infuriating ("Maven is a device for reducing grown men to sobbing masses of absolute terror") it is because they assume too much control over the process flow.

But what mystifies me in retrospect is that I did not always feel this way. I used to feel insecure over my dislike of tools. In the same way that a novice C++ programmer when quickly shot down for their ignorance of sequence points is unlikely to question the philosophical rationale of even having sequence points, I assumed that the reason for my dislike of tools was due to my lack of mastery with tools, my lack of strength in the face of tools, and my lack of knowledge for the design considerations behind tools.

And yet somehow, when I did master a tool, enough to build my own tool around the tool, I still didn't like the tool.

I didn't quite understand why; I thought I had simply bumped against architectural mistakes in docutils; I didn't realize that the problem was that it was a tool, and that by wrapping it in my own tool I was in fact making the situation worse.

The moral became apparent while I was drafting a Makefile to build some code that used to be managed by TI Code Composer Studio (note the URL) and compiled with TI Code Generation Tools. The compiler cl6x for Code Generation Tools has perhaps the most mischievous command line interface I have ever encountered. Its rules for the naming of output files (which sometimes permit explicit overriding and sometimes not), which files must be built in a common invocation, and what must be the working directory are like carefully placed traps, and make has a habit of stepping everywhere.

And then, I decided, I don't have to write a Makefile. Nor must I use make or Scons or CMake or redo or any build tool at all. I can write a Python script that invokes the appropriate commands, and that's it.

And I won't sacrifice incremental build, because I can add memoization, and I won't sacrifice selectable targets because I can use argparse for command line arguments, and I won't sacrifice wildcards and path substitutions because I can write a few Python functions for manipulating paths and that's all I need (os.path does most of the work).

A skilled Makefile writer will point out that the job would have been easy in make if you knew what you were doing. That's probably true. But the lesson to be learned is that we no longer need to feel bad that we didn't know what we were doing with make, we can get the job done in pure Python and nobody need ever know what they are doing, beyond what they are actually in reality doing.

Building on this philosophy I wrote scooter, which I think in retrospect contains some mistakes that bring it a little too close to being a tool (such as using exclusively inotify for dependency tracking), but it is at least a step in the right direction. The project quickfiles that came out of it is better.

As a tool-less conclusion I present you the simplest possible HTML document generator for Python:

  1  def surround_with(start, end):
  2      def dec(f):
  3          print(start)
  4          f()
  5          print(end)
  6      return dec

Because that really is all you need, and does 50% of the work that docutils or Sphinx or LaTeX do, without requiring any new knowledge (everyone has to learn HTML at some point in their lives). Add in this function:

  7  def pyplot_image(**fig_attrs):
  8      from matplotlib.pyplot import figure
  9      def dec(f):
 10          fig = figure(**fig_attrs)
 11          f()
 12          tmp = Path.mktemp().setext('.png')
 13          fig.savefig(str(tmp))
 14          data = b64encode(open(str(tmp)).read())
 15          print('<img src="data:image/png;base64,%s"/>' % (data,))
 16      return dec

And you have everything you need to autogenerate reports of analyses including plots, as a standalone HTML document with no external dependencies, that you can email to someone, that will display in any browser.

[1]Otherwise make -n would be much harder.

1 comment:

  1. "there simply isn't a substitute for Maven right now"

    I would say SBT is a great substitute in most cases. The main use case is to use it to build your Scala project, but it's also made to handle any kind of Java/Scala mix in a project.

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