fix(fast-inbox): include the message-only block-root proof in the ProvingJobResult schema (A-1375)

BLOCK_ROOT_MSGS_ONLY_ROLLUP was added to the enum, the ProvingJobInputs union, and the
result type map, but omitted from the ProvingJobResult discriminated union. A checkpoint
that builds a message-only block produces this proof output, which the proof store then
fails to decode with an invalid-discriminator error, stalling proving. Add the missing
union member, mirroring the other block-root results. Adds a schema round-trip regression
test.

Author: spalladino

yarn-project/stdlib/src/interfaces/proving-job-source.test.ts

@@ -1,16 +1,19 @@
 import { NESTED_RECURSIVE_ROLLUP_HONK_PROOF_LENGTH } from '@aztec/constants';
 import { EpochNumber } from '@aztec/foundation/branded-types';
+import { jsonParseWithSchema, jsonStringify } from '@aztec/foundation/json-rpc';
 import { type JsonRpcTestContext, createJsonRpcTestSetup } from '@aztec/foundation/json-rpc/test';
 
 import { ProvingRequestType } from '../proofs/proving_request_type.js';
 import { makeRecursiveProof } from '../proofs/recursive_proof.js';
+import { BlockRollupPublicInputs } from '../rollup/block_rollup_public_inputs.js';
 import { TxRollupPublicInputs } from '../rollup/tx_rollup_public_inputs.js';
+import { makeBlockRollupPublicInputs } from '../tests/factories.js';
 import { VerificationKeyData } from '../vks/verification_key.js';
 import { type ProvingJobSource, ProvingJobSourceSchema } from './proving-job-source.js';
 import {
   type ProofUri,
   type ProvingJob,
-  type ProvingJobResult,
+  ProvingJobResult,
   type ProvingRequestResultFor,
   makePublicInputsAndRecursiveProof,
 } from './proving-job.js';
@@ -63,6 +66,28 @@ describe('ProvingJobSourceSchema', () => {
   });
 });
 
+describe('ProvingJobResult', () => {
+  it('round-trips a message-only block-root rollup result through the schema', () => {
+    // The message-only block-root proof type must survive serialization: a checkpoint that builds a message-only
+    // block produces this result, and the proof store decodes it via the ProvingJobResult schema. Omitting it from
+    // the union throws "Invalid discriminator value" and stalls proving.
+    const result: ProvingJobResult = {
+      type: ProvingRequestType.BLOCK_ROOT_MSGS_ONLY_ROLLUP,
+      result: makePublicInputsAndRecursiveProof<
+        BlockRollupPublicInputs,
+        typeof NESTED_RECURSIVE_ROLLUP_HONK_PROOF_LENGTH
+      >(
+        makeBlockRollupPublicInputs(),
+        makeRecursiveProof(NESTED_RECURSIVE_ROLLUP_HONK_PROOF_LENGTH),
+        VerificationKeyData.makeFakeRollupHonk(),
+      ),
+    };
+
+    const roundTripped = jsonParseWithSchema<ProvingJobResult>(jsonStringify(result), ProvingJobResult);
+    expect(roundTripped.type).toEqual(ProvingRequestType.BLOCK_ROOT_MSGS_ONLY_ROLLUP);
+  });
+});
+
 class MockProvingJobSource implements ProvingJobSource {
   getProvingJob(): Promise<ProvingJob | undefined> {
     return Promise.resolve({

yarn-project/stdlib/src/interfaces/proving-job.ts

@@ -277,6 +277,13 @@ export const ProvingJobResult = z.discriminatedUnion('type', [
       NESTED_RECURSIVE_ROLLUP_HONK_PROOF_LENGTH,
     ),
   }),
+  z.object({
+    type: z.literal(ProvingRequestType.BLOCK_ROOT_MSGS_ONLY_ROLLUP),
+    result: schemaForPublicInputsAndRecursiveProof(
+      BlockRollupPublicInputs.schema,
+      NESTED_RECURSIVE_ROLLUP_HONK_PROOF_LENGTH,
+    ),
+  }),
   z.object({
     type: z.literal(ProvingRequestType.BLOCK_MERGE_ROLLUP),
     result: schemaForPublicInputsAndRecursiveProof(