fix(foundation): always include a result key in json-rpc responses

[aminsammara]

Problem

The safe JSON-RPC server built success responses as { jsonrpc, id, result }. When a handler returns undefined, JSON.stringify drops the result key, producing {"jsonrpc":"2.0","id":N} — a response with neither result nor error, which violates JSON-RPC 2.0 and leaves raw/external callers unable to tell "not found" from a malformed reply.

Surfaced via node_getContract on an undeployed (but valid) address: the response had no result field at all.

Fix

One line in the shared server (safe_json_rpc_server.ts): coerce an undefined return to null (result: result ?? null, so 0/false/'' are preserved). The result key is now always present.

Blast radius

Framework-level, so it fixes every method that can return undefined — ~20 on the node interface (getContract, getContractClass, getTxEffect, getTxByHash, getBlock, the witness getters, synced slot/epoch, validator stats, …) plus every other server on this framework (PXE, prover-node, archiver). Void methods now also return result: null.

Why it's safe for existing clients

The TS client short-circuits null/undefined/'null'/'undefined' before schema validation, so it never runs null through an .optional() schema — omitted vs result: null both resolve to undefined client-side. Only raw/external callers change, and they now get a spec-compliant response.

Testing

• Added a test: a handler returning undefined now yields { jsonrpc, result: null } (red before, green after).
• Updated the existing void-method (clear) assertions, single and batch, to the new shape.
• Added integration tests (test/integration.test.ts) pinning that optional result schemas tolerate null responses:
  • end-to-end: the wire response for an undefined return carries an explicit result: null, and the safe client resolves it to undefined;
  • client-isolated: a stubbed fetch returning result: null verbatim resolves to undefined against an .optional() schema instead of throwing a ZodError. Both go red if the client's null short-circuit is removed (verified: Invalid input: expected object, received null).
• Full json-rpc suite: 102 passed; foundation lint clean.

[AztecBot]

✅ Successfully ported to port-to-next-staging #24964.