Double-braces incorrectly trigger braces/min-spaces-inside

[sbrowne-godaddy]

When using the following snippet of .yamllint:

---
extends: default
  braces:
    min-spaces-inside: 1
    max-spaces-inside: 1

A YAML file that has a value with double braces incorrectly triggers:

---
keyname: {{ value }}

The output is as such:

[user@laptop sceptre (master)]$ ~/.cache/pre-commit//repo7_jyo6cg/py_env-python3.13/bin/yamllint test.yaml 
test.yaml
  2:11      error    too few spaces inside braces  (braces)
  2:20      error    too few spaces inside braces  (braces)

A quick flick through the spec doesn't immediately reject the use of {{.

In particular, Sceptre (for AWS CloudFormations) make use of this form of double-brace.

It would be nice if this could either be handled by default or a new rule could be created to allow for it to treat them as single-brace (for linting purposes).

[user@laptop sceptre (master)]$ ~/.cache/pre-commit//repo7_jyo6cg/py_env-python3.13/bin/yamllint --version
yamllint 1.37.1

[adrienverge]

Hello Stuart,

Your example:

---
keyname: {{ value }}

is not valid YAML: {{ is forbidden because a { starts a mapping and should be followed by a key-value pair, or an end of mapping (}). Parsing with a parser (for instance PyYAML) fails:

Traceback (most recent call last):
  …
    raise ConstructorError("while constructing a mapping", node.start_mark,
            "found unhashable key", key_node.start_mark)
yaml.constructor.ConstructorError: while constructing a mapping

I guess this snippet is a Jinja2 template, meant to be transformed into valid YAML by Sceptre. It pre-processes templates to transform {{ … }} and {% if … %} and produce a valid YAML document.

See similar cases in already-existing issues: #61, #65, #128, #311, #408, #460, #462, #507, #531, #547…
In those issues you'll find workarounds that work in some cases. In your precise case, quoting the value could work:

---
keyname: '{{ value }}'