on and off are incorrectly interpreted when they are keys

[jason-s]

on and off are interpreted as True or False when used as values. But they are also interpreted this way as keys:

C:\>python
Python 2.7.12 |Anaconda 4.1.1 (64-bit)| (default, Jun 29 2016, 11:07:13) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
Anaconda is brought to you by Continuum Analytics.
Please check out: http://continuum.io/thanks and https://anaconda.org
>>> import yaml
>>> yaml.safe_load("""
... on: 1
... off: 2
... """)
{False: 2, True: 1}
>>> yaml.__version__
'3.11'

[jason-s]

It doesn't seem to follow the YAML spec (at least not the YAML 1.1 boolean spec) consistently in this regard:

>>> yaml.safe_load("""
... y: 1
... n: 2
... """)
{'y': 1, 'n': 2}
>>> yaml.safe_load("""
... yes: 1
... no: 2
... """)
{False: 2, True: 1}
>>>

[jason-s]

>>> for k in "y|Y|yes|Yes|YES|n|N|no|No|NO|true|True|TRUE|false|False|FALSE|on|On|ON|off|Off|OFF".split("|"):
...   print k, yaml.safe_load("%s: 1" % k)
...
y {'y': 1}
Y {'Y': 1}
yes {True: 1}
Yes {True: 1}
YES {True: 1}
n {'n': 1}
N {'N': 1}
no {False: 1}
No {False: 1}
NO {False: 1}
true {True: 1}
True {True: 1}
TRUE {True: 1}
false {False: 1}
False {False: 1}
FALSE {False: 1}
on {True: 1}
On {True: 1}
ON {True: 1}
off {False: 1}
Off {False: 1}
OFF {False: 1}

[mjrk]

@jason-s these aliases for booleans are reserved YAML keywords. This counts for keys, too, and other implementation also interpret them as booleans. If you want the string value, you have to wrap them in quotation marks.

>>> import yaml
>>> yaml.safe_load("""
... "no": test
... """)
{'no': 'test'}
>>> yaml.safe_load("""
... no: test
... """)
{False: 'test'}

However, the handling of y/n indeed seems to be inconsistent.

[wirecat]

@mjrk Even then, why would anyone want their YAML library to automatically change a key name? That doesn't make any sense to me. I understand it for values, but not keys.

e: I don't see On or Off as keywords in the spec: https://yaml.org/spec/1.2/spec.html#id2803629

[perlpunk]

e: I don't see On or Off as keywords in the spec: https://yaml.org/spec/1.2/spec.html#id2803629

PyYAML currently only implements YAML 1.1:
https://yaml.org/type/bool.html

[perlpunk]

Even then, why would anyone want their YAML library to automatically change a key name?

If a language like Python supports other types than strings as dictionary keys, like booleans or None, why not?

true: value 1
false: value 2
null: value 3

YAML makes no difference between keys and values in this regard.

[wirecat]

@perlpunk Touche. I personally wouldn't want my keys being transformed like that, but it makes sense that some might.

I didn't realize this library only supported 1.1 and that explains my confusion.

Seems like there isn't an issue here and this could be closed?

[nitzmahone]

@wirecat it's also trivial to swap in a custom resolver to your own Loader composition to alter or remove that behavior any way you'd like: https://github.com/yaml/pyyaml/blob/master/lib3/yaml/resolver.py

The lack of support for y/n is already tracked on #247, so I'm going to go ahead and close this (since the rest is working as-designed).