[ericproulx]

declared answers, for each param an endpoint declares, the key it is filed under (its name, or the one as: gave it) and the empty value it stands for when it was not sent (an Array, a Set or a Hash, after its documented type). Neither depends on the request, yet both were worked out again on every call, for every declared param:

• the path to the param was built to look its new name up,
• its documented name (address[geo][lat]) was spelled out to look its type up,
• that type was matched against the ones that have an empty value,
• and for a Hash, every documented param was scanned for a child.

Grape::DeclaredParams now holds those answers per endpoint. Endpoint#compile! builds it, as it builds Validations::UndeclaredParams, and DeclaredParamsHandler walks its params against the ones the request sent. An empty value is copied on every call, so no two requests share one.

Numbers

Interleaved A/B from one checkout, median of per-round pairs over 6 rounds. In parentheses, the rounds the branch won.

request	interpreter	YJIT
POST, 23 params declared, 4 of the 15 top-level ones sent, declared(params)	+29.7% (6/6)	+42.9% (6/6)
the same, declared(params, include_missing: false)	+10.6% (6/6)	+5.5% (6/6)
POST, 10 params with a Hash and an Array of three Hashes, all sent, declared(params)	+10.0% (6/6)	+7.6% (6/6)
PUT by id, 9 params, one a Hash, all sent, declared(params, include_missing: false)	+5.7% (6/6)	+5.1% (6/6)
the 23 params again, on a route that does not call declared (control)	-0.4%	+0.7%
route with no params (control)	+0.6%	+1.5%

On the first row declared itself goes from 29.9 to about 13 µs on the interpreter.

Cost

The params are compiled for every endpoint, whether or not it calls declared: nothing at compile time says that it will. On an API of 600 endpoints declaring 12 params each, compiling goes from 289 to 300 ms and retained memory from 11.6 to 12.2 MB.

What changes

Compared with master over random declarations, payloads and every combination of declared's options, about 900,000 calls: the same answer wherever master answered. In two cases master raised, and the branch answers:

• A param that desc ..., params: documents by hand with a type that is not a String (a Class, say), or with something other than a Hash of details, has no empty value. declared raised NoMethodError or TypeError when such a param was not sent.
• An optional param named from configuration has no name while the API is called unmounted. declared raised NoMethodError on nil.to_sym there, and now files the param under nil. Mounted, nothing changes.

DeclaredParamsHandler#call takes the compiled params in place of the declared params, the documented ones and the renames. Nothing else in Grape, grape-entity or grape-swagger calls it.

No contract change, so no UPGRADING entry.

🤖 Generated with Claude Code