ImportWizardProps.dataSource is required, but every read of it in the component is defensive #4320

Found while wiring @object-ui/plugin-grid's tests into tsc for #4040 (tranche 2, PR #4297). Recorded rather than changed: it is a public exported interface, and #4040's standing rule is to stop and file when a public type looks wrong rather than guess at it.

What the compiler said

ImportWizardProps.dataSource (packages/plugin-grid/src/ImportWizard.tsx:292) is declared dataSource: any — required. src/__tests__/importMissingRequiredHint.test.tsx omitted it, which is what the newly-compiled test project reported:

src/__tests__/importMissingRequiredHint.test.tsx(35,6): error TS2741: Property 'dataSource' is missing in
type '{ objectName: string; fields: …[]; open: true; onOpenChange: () => void; }'
but required in type 'ImportWizardProps'.

PR #4297 fixed the fixture (it passes a capability-free {}), which is the right fix for that test and is where the matter ends for #4040.

The observation

The fixture was omitting it and the wizard rendered fine — because every read of dataSource inside the component is guarded. There is no unguarded dereference anywhere in the file:

• const ds = dataSource as Partial< DataSource > | undefined; — three times (:1432, :1632, :1883)
• (dataSource as { listImportMappings?: … } | undefined)?.listImportMappings (:1673)
• if (dataSource?.create) await dataSource.create(…) (:1861)
• typeof (dataSource as Partial< DataSource > | undefined)?.listImportJobs === 'function' (:2188), and the same shape for importRecords (:2303) and cancelImportJob (:2353)

So the implementation's real contract is "optional, and every capability on it is optional too" — the wizard degrades from the server import path to the per-row create loop to nothing at all — while the declaration says "required". The two disagree, and the ones written in the defensive style are the ones the code actually obeys.

Why this is an observation and not a defect

No user meets it. Every real caller passes a data source, and the declaration being stricter than the implementation fails safe: it can only reject a call the component would have survived, never accept one it cannot. It cost one test fixture a line, and that line is now written.

It is worth a card anyway because the mismatch is the kind that decides a later question wrongly: someone reading dataSource: any as required will not know that a dataSource-less embed is a supported shape (and someone reading the guards will not know whether they are load-bearing or superstition). Both readings are currently defensible from the source, which is the actual problem.

If it is ever picked up

Two coherent resolutions, and the choice is a contract call, not execution:

• Make it optional (dataSource?: DataSource) — matches the implementation, and lets a caller mount the wizard for its parse/mapping steps alone. Widens the accepted surface.
• Keep it required and drop the guards — makes the implementation match the declaration, and turns the currently-silent "no capability" paths into something a caller can reason about. Narrows the code.

Either way any is worth replacing with DataSource: the component already casts to Partial< DataSource > at five sites to get any checking back, which is the declaration admitting the type it wants.

Refs #4040, #4297.