The YAML-Norway Law

Posted on Jun 20, 2018

tl;dr: Anyone who uses YAML long enough will eventually get burned when attempting to abbreviate "Norway."

YAML Ain’t Markup Language (YAML) is a human-readable data serialization language, and if you ever try to abbreviate “Norway,” you just might run into a surprising outcome.

Here’s an example:

NI: Nicaragua
NL: Netherlands
NO: Norway # boom!

Does it work? NO|No|no, but not “NO”. NO is parsed as a boolean type, which with the YAML 1.1 spec, there are 11 ways to say false:

n
N
no
No
NO
false
False
FALSE
off
Off
OFF

The correction:

NI: Nicaragua
NL: Netherlands
'NO': Norway

This has been fixed in the YAML 1.2 spec, but many YAML parsers still use 1.1 by default.

Personally, I don’t mind YAML. It makes things easy. But, this, along with many of the design decisions in YAML strike me as a simple vs. easy tradeoff, where the authors opted for “easy,” at the expense of simplicity. I, and I assume many others, mostly use YAML for configuration. I want and need my config files to be dead simple, explicit, and predictable. YAML isn’t perfect, and the authors humbly acknowledge that. But when it comes to config, “easy” (and the unexpected surprises that come with it) can take a back seat.