The Emacs Problem (opens in new tab)

Here is what a make file should look like:

1) vpath statements for various file extensions

2) Phony targets for logical build units, including "all"

3) Generic rules for mapping .abc to .xyz; these rules should have exactly one line of code which executes an external script/tool

4) A list of edges in the dependency graph

5) A few variables as necessary to eliminate redundant edges

If you put any logic in your Makefiles, you are doing it wrong.

If your builds are slow, add empty dummy files for larger culling by timestamps. If timestamps are insufficient, codify early out logic into tools.

Not having logic in my Makefiles enables parallel execution and strong support for incremental builds. If I were to use Lisp as a build system, I'd create a DSL that had these same properties; forbidding arbitrary logic in my dependency graph. It's about finding the right balance to inject expressiveness without losing desirable properties of the DSL. This is why every developer needs to understand more about programming language design. Anytime you create any type of file format, you are doing it. And anytime you are writing any type of file format, you are reverse engineering it. Understanding the intended separation of logic for Makefiles helps me write better Makefiles.

The way it works is that their are no mandatory newline characters in JSON. Whitespace between lexical elements is ignored, and any embedded newlines in strings can be escaped (i.e. as \n). So a log format that a few people are using today is like this:

{'kind': 'foo', 'id': 1, 'msg': 'hi'} {'kind': 'bar', 'id': 2, 'msg': 'there'}

Each log message takes up a single line in the file. You can trivially deserialize any line to a real data structure in your language of choice. You can (mostly) grep the lines, and they're human readable. I do this at work, and frequently have scripts like this:

scribereader foo | grep 'some expression' | python -c 'code here'

In this case we're storing logs in the format described above (a single JSON message per line), and scribereader is something that groks how scribe stores log files and outputs to stdout. The grep expression doesn't really understand JSON, but it catches all of the lines that I actually want to examine, and the false positive rate is very low (<0.1% typically). The final part of the pipe is some more complex python expression that actually introspects the data it's getting to do more filtering. You can of course substitute ruby, perl, etc. in place of the python expression.

I feel like this is a pretty good compromise between greppability, human readability, and the ability to programatically manipulate log data.

And now anyone who can modify your log can execute arbitrary code in the reader process…

There is a point to be made for the idea that you are solving the wrong problem with the log parsing. On the other hand, if you are trying to interface with other developers' popular engines, you may not have a choice.

It takes a lot of pain out of XML processing. Don't have to remember the specifics of XPath/XQuery but you still have to deal with the pain of multiple namespace resolution inherit in XML.