Support equality and inequality operators in YAML access policy conditions

[igorlukanin]

Is your feature request related to a problem? Please describe.

In data access policies, the if expression of an access_policy condition supports a different set of operators depending on the data model format:

• In JavaScript data models, the if expression is evaluated as a JavaScript expression, so comparison operators such as ===, !==, ==, and != work.
• In YAML data models, the { ... } expression is evaluated as a Python expression by Cube's expression transpiler, which currently supports only logical operators (and, or, not), member access, and method calls. Comparison operators are not supported.

For example, this works in a JavaScript model:

conditions: [
  { if: securityContext.region === `EMEA` }
]

But the equivalent YAML fails to compile:

conditions:
  - if: "{ securityContext.region == 'EMEA' }"

with an error like:

Failed to parse Python expression. Most likely this type of syntax isn't supported yet: Unsupported Python multiple children node: Comp_opContext: ==

This is the most common gap: comparing a security context value to a literal (e.g. securityContext.region == 'EMEA') is a very natural way to express a condition, and today it can only be done in JavaScript models. Users on YAML models have to work around it by pushing the comparison into a boolean user attribute or method call.

Describe the solution you'd like

Support equality and inequality operators (==, !=) in the YAML if expressions of access policy conditions, transpiling them to their JavaScript equivalents (===, !==), so that YAML and JavaScript models are at parity for these operators.

Describe alternatives you've considered

• Using a JavaScript data model instead of YAML (works, but not always desirable).
• Precomputing the comparison as a boolean user attribute in the security context (works, but pushes model logic out of the data model).

Additional context

This is tracked from the docs side: the supported operators table now documents which operators work in each format. Comparison, arithmetic, and other operators are similarly unsupported in YAML, but equality/inequality is the most impactful gap. Please 👍 or comment if you'd like this — it helps us prioritize.