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Validation

Specification > Engineering

This chapter defines how public methods validate their inputs: one dedicated validation method per public method, one concern per request, a strict check order, and a uniform bulk-check pattern. It is conditional and applies to the JavaScript sources covered by the stack chapter.

One Validator per Method

Section titled “One Validator per Method”

Each public method MUST have exactly one dedicated validation method, and a single validation request MUST address a single concern. You MUST NOT widen a validator’s scope beyond the method it guards.

Check Order

Section titled “Check Order”

A validator MUST run its checks in a strict order and stop at the first failure:

StepCheck
1Existence — the required value is present.
2Early break — return immediately once a required value is missing.
3Detail — type, shape, and membership checks on the values that exist.

Bulk-check Pattern

Section titled “Bulk-check Pattern”

When a method validates many fields, you MUST express each field as a [ key, value, type, list ] tuple and check the set uniformly. Errors raised for array members MUST carry the offending index:

const checks = [
    [ 'id', id, 'string', [] ],
    [ 'role', role, 'string', [ 'admin', 'user' ] ],
    [ 'tags', tags, 'array', [] ]
]


const errors = []
checks.forEach( ( [ key, value, type, list ], index ) => {
    if( type !== 'array' && typeof value !== type ) {
        errors.push( `[${ index }] ${ key }: expected ${ type }` )
    }
    if( list.length > 0 && !list.includes( value ) ) {
        errors.push( `[${ index }] ${ key }: not in allowed list` )
    }
} )

In each tuple, key names the field, value is the candidate, type is the expected type, and list is the optional set of allowed values; an empty list means there is no membership constraint.

Reporting

Section titled “Reporting”

A validator MUST return a structured result (for example { status, errors }) rather than a bare boolean, so a caller can read both the verdict and the per-field reasons.

Section titled “Related”