Summary

Since atomic rule, chain rule, nested rule, and transformers are treated generically as rule, they can be composed together in all sorts of ways.

Most time, bcx-validation treats expression and function exchangeable. There are two special cases:

In if transformer, {if: "conditionExpression"} only supports expression as condition. This is to avoid ambiguousness. If you want to validate a nested property named “if”, you can use {if: aFunction} or {if: {validate: "fullShapeRule"}} or {if: ["aliasInChain", ...]}.

In foreach transformer, top level function is a rule factory, not raw validator.

bcx-validation’s rule format is simple and readable, it always tries to understand what you want.

But when validating some property name that’s one of bcx-validation’s reserved keys, it could be ambiguous. Like validating property named “validate” with “mandatory” validator: {validate: "mandatory"} (bcx-validation would not see it as your intended nested validation).

Reserved keys are validate, value, message, stopValidationChainIfFail, stopValidationChainIfPass. Plus if, switch, foreach, key, introduced by standard transformers.

The easy way to avoid ambiguousness is to use either full shape, or wrap it in a chain, {validate: {validate: "mandatory"}} or {validate: ["mandatory"]}. This works for all our reserved keys.

Note foreach and key works in a pair. Either they are recognised as foreach transformer as a whole, or recognised as nested validation on property “foreach” and “key”.

Happy validating!