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Ability to provide type hints to non-identifier keys #871
Description
Consider a JSON object
{
"with-hyphen": "a-string",
"$startsWithDollarSign": 123
}Problem: It's not possible to provide type-hints for with-hyphen and $startsWithDolalrSign
CEL can get type information well if we can express an object as protobuf, or use StructType. However, there are times when we have objects that have non-identifier keys.
Right now, it's not possible to provide typesafety for non-identifier keys.
It would be amazing if we could.
Alternatives considered
To solve this for ourselves, we considered to hacks:
- Use aliases: walk the CEL tree, and rename all non-identifer keys to some known identifer-style key.
- Run our own compile step validation: walk the cel tree, and do the type checking ourselves.
Right now we are going with 2., but if there was some built-in way to specify types for keys from index access, it would be amazing.
Activity
[-]Ability[/-][+]Ability to provide type hints to non-identifier keys[/+]l46kok commentedon Nov 21, 2025
As an alternative: you could toggle the following option to allow backticks as an escape mechanism to allow field accesses outside normal identifiers for structs/protobufs: https://github.com/google/cel-java/blob/main/common/src/main/java/dev/cel/common/CelOptions.java#L272
Though at the moment, "$" isn't supported, but this is something we could add:
https://github.com/google/cel-java/blob/d7ad94d02c982fd465fcf472802a5be87766ff18/parser/src/main/java/dev/cel/parser/gen/CEL.g4#L207
More generally, we considered adding first-party support for JsonSchema and Open API schema. That would address this use case. I'll keep this open until we add that in.