capnweb-validate: ignore extra args instead of refusing the call - #227
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Extra args past a method's declared parameters no longer fail the call: a
newer caller passing a parameter this build's signature doesn't know about is
normal schema evolution in JS/TS.
Ignored means the implementation never sees them. Args past what the spec
declares are dropped before the call, so the impl cannot read a value no
validator checked:
// spec generated from: greet(name: string)
greet(name: string, ...rest: unknown[]) { /* rest is always empty */ }
// spec generated from: sum(label: string, ...values: number[])
sum(label: string, ...values: number[]) { /* gets every arg, each validated */ }
Truncation only applies when the spec declares its params; a client-side spec
omits `args` entirely, so nothing is dropped there.
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dimitropoulos
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I'm not 100% sold on the premise - but I understand the reasoning. maybe later it can be configurable (strict mode?)
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let's document allowable evolution places (e.g. extra args, extra fields).
Adds a Schema Evolution section to the validate README: which type changes survive a version skew between peers, that extra object properties reach the implementation unvalidated while extra arguments are dropped, and that building without strictNullChecks emits a validator that refuses null values a strict peer considers valid.
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validateArgsrefused any call carrying more args than the method's declared parameter list. That breaks schema evolution: a caller built against a newer signature cannot pass a new parameter to a peer whose validator was generated from the old one, even though plain JS drops the unused arg.Before:
After:
Declared parameters are still validated, and a rest parameter still validates every extra arg.