Conditionally required¶

conditionallyRequired enforces that a set of fields becomes required when a controlling field matches a specific value.

If the condition is met and any required field is missing or rejected, the rule emits a boundary‑level error for each missing field. This rule is ideal for type‑driven shapes, mode‑dependent configurations, and any scenario where additional fields become mandatory only under certain conditions.

Signature¶

export function conditionallyRequired(
    typeKey: string,
    typeValue: unknown,
    ...required: string[]
): BoundaryRule

Parameters¶

Parameter	Data type	Description
`typeKey`	`string`	The controlling field whose final value determines whether requirements apply.
`typeValue`	`unknown`	The value that triggers the requirement set.
`required`	`string[]`	The fields that must be accepted when the condition is met.

Events¶

Event code	Description
`boundary.does.require-field`	A required field was missing or rejected under the condition.

Design rationale¶

Activates only when the controlling field’s final value equals the specified trigger value.
Emits one error per missing field, ensuring precise contributor feedback.
Evaluates required fields strictly by acceptance (decision.code === "accept").
Does not modify field values or decisions — it only adds boundary‑level issues.
Supports clear, declarative modeling of conditional schemas.

Invoke¶

conditionallyRequired runs during the boundary decision phase. It is not affected by normalization mode or parsing rules.

The rule activates when:

fields[typeKey]?.final strictly equals typeValue.
Any of the required fields are missing or not accepted.

Examples¶

Condition met — all required fields present¶

conditionallyRequired("kind", "email", "address", "verified");

// kind = "email"
// address accepted
// verified accepted
// → OK (no boundary issues)

Condition met — missing required fields¶

conditionallyRequired("kind", "email", "address", "verified");

// kind = "email"
// address accepted
// verified missing
// → boundary.does.require-field at $.verified

Condition not met — rule does nothing¶

conditionallyRequired("kind", "email", "address");

// kind = "sms"
// → no required‑field checks performed