Better YAML

[abitrolly]

YAML is not always readable. Here is an example of build config from Travis that failed, because of YAML parsing.

script: 
  - echo "default shell: $SHELL"

To see what's wrong, let's use https://yaml-online-parser.appspot.com/ to convert it to Python.

>>> a = {'script': [{'echo "default shell': '$SHELL"'}]}

The logical way to get the first command to be executed it to get the first element from the script: array.

>>> a['script'][0]
{'echo "default shell': '$SHELL"'}

But wait, it is a dict. Should it be the string?

>>> b['script'][0]
'echo "default shell: $SHELL"'

The correct YAML for b needs the whole line to be quoted.

script: 
  - 'echo "default shell: $SHELL"'

Otherwise YAML splits the command on the first found colon :. It doesn't understand internal " quoting.

Solution

"Better" YAML should not allow any spaces in dict keys and spaces between the key and the colon.

echo: hello

then will still be equal to

{'echo': 'hello'}

But these will be just plain strings.

echo  :   hello

echo "say: hello"

Maybe HashiCorp HCL was born to be the Better YAML because of this gotcha.