Packages / validation · source
Validation written on the fields it validates.
@validated
class Ask {
@required("a site key is needed")
@maxLength(200, "that is not a site key")
siteKey: string;
@min(1, "at least one try")
@max(10, "ten tries is the ceiling")
tries: int;
}let wrong = faults(Class.decorator(new Ask(...), "validated"), req.body);
if (wrong.length > 0) { return badRequest(faultsJson(wrong)); }
let ask = JSON.parse<Ask>(req.body);faults returns every fault, each naming its field:
[{"field":"siteKey","said":"that is not a site key"},
{"field":"tries","said":"ten tries is the ceiling"}]A client fixing three mistakes makes one round trip, and a handler can branch on field rather than matching on prose.
Shapes. JSON.parse<T> already refuses a body that omits a declared field, sends one the type does not name, or sends the wrong kind of value, and it names the field (spec 483). This is only for what a type cannot say: how long, how many, how few.
So the two run in order — values first, because the messages are yours, then the parse, whose refusal is the library's.
| annotation | holds when |
|---|---|
@required(said) | the field is present and not blank |
@maxLength(n, said) | at most n bytes |
@minLength(n, said) | at least n bytes, when present |
@max(n, said) | at most n |
@min(n, said) | at least n |
The message is optional. Without one a rule still says which field and what it wanted, so a forgotten message is a plainer sentence rather than a silent pass.
@validated runs while compiling. It is handed every field and every annotation written on it, and leaves a Rule[] constant the class carries; faults reads that at run time through Class.decorator. Nothing is scanned or reflected on at run time, and nothing about the class survives into the binary that was not already there.
Arguments arrive through argsText (spec 484): @maxLength(200, "…") mixes an int and a string, and a Lumen array is homogeneous, so the description carries every argument spelled as text and this package parses back the number.
cd packages/validation
lumen test validation.test.ts # 7