Say undefined where the SMSC named no id for a segment it took (#101)

* Cover the ids a send gets back where the SMSC named only some of them

* Say undefined where the SMSC named no id for a segment it took

* Record why the merger takes the wider type, and de-duplicate the interop narrowing

* Guard the numbering hole the merger must refuse, and correct the phase record

interop-tests/findings/09-operator-fixtures.md

@@ -177,9 +177,9 @@ the fixtures pin that a reader would not otherwise expect:
   application wanting one report per message compares each `dlr.smsId` against the `smsIds` array
   `sendSms()` returned and merges them itself.
 - **Telesign answers only the first segment of a concatenated submit with a `message_id`.**
-  `sendSms()` returns `['<id>', '', '']` — one entry per segment, positional with `pduObjs`, empty
-  where the SMSC named nothing. `dlr.smsId` is never empty, so an empty entry matches no receipt,
-  and no merge is armed.
+  `sendSms()` returns `['<id>', undefined, undefined]` — one entry per segment, positional with
+  `pduObjs`, `undefined` where the SMSC named nothing; it returned `''` there until #101.
+  `dlr.smsId` is never empty, so an unnamed entry matches no receipt, and no merge is armed.
 
 ## Open questions
 
@@ -203,6 +203,5 @@ the fixtures pin that a reader would not otherwise expect:
   `FAILED` and CM.com's `DELIVERD`. The documented-codes table in `operator-receipts.test.ts` is
   the place a new one goes, and it fails loudly for anything nothing names.
 - Whether `smsIds` carrying an empty entry for a segment the SMSC took but named no id for is the
-  right shape for a caller, or whether that case wants saying differently. It is documented in
-  `README.md` and pinned by the Telesign scenario; the question is a product one, not a correctness
-  one, and belongs to the phase 11 product-owner pass.
+  right shape for a caller. Settled in #101: the entry is `undefined`, and the decision with its
+  rejected alternatives is recorded in `AGENTS.md`.

interop-tests/jasmin.test.ts

@@ -476,6 +476,7 @@ describe('C3+C7 - long MT through the fake upstream, receipts and id consistency
 			assert.equal(sent.smsIds.length, testCase.expectedSegments);
 
 			for (const id of sent.smsIds) {
+				assert.ok(id, 'expected Jasmin to name a message id for every segment');
 				assert.match(id, uuidPattern, 'expected a UUID-shaped message id from Jasmin\'s submit_sm_resp');
 
 				// The full round trip - submit_sm to Jasmin's smpps, mtrouter, AMQP, the connector bind,

interop-tests/smppsim.test.ts

@@ -97,6 +97,15 @@ function dlrLooksIntact(received: Received | undefined): received is Received {
 		&& received.pduObj.tlvs.message_state?.tagValue !== undefined;
 }
 
+/** SMPPSim names an id for every segment, so an unnamed one is the finding, not the norm. */
+function namedIds(smsIds: (string | undefined)[]): string[] {
+	const ids = smsIds.filter(id => id !== undefined);
+
+	assert.equal(ids.length, smsIds.length, 'expected SMPPSim to name a message id for every segment');
+
+	return ids;
+}
+
 /**
  * Resends a fresh message until one attempt's segments are every one matched by an intact `dlr`.
  * Retrying works around the peer+library interaction above without hiding it: a scenario only
@@ -119,12 +128,14 @@ async function sendUntilAllDlrsArrive(
 
 		assert.equal(sent.err, undefined);
 
+		const ids = namedIds(sent.smsIds);
+
 		const complete = await waitFor(
-			() => (sent.smsIds.every(id => dlrLooksIntact(dlrs.find(r => r.dlr.smsId === id))) ? true : undefined),
+			() => (ids.every(id => dlrLooksIntact(dlrs.find(r => r.dlr.smsId === id))) ? true : undefined),
 			DLR_RETRY_BUDGET_MS,
 		);
 
-		if (complete) return sent.smsIds;
+		if (complete) return ids;
 	}
 
 	throw new Error(`no attempt got an intact DLR for every segment within ${String(DLR_MAX_ATTEMPTS)} tries`);
@@ -149,14 +160,16 @@ async function sendUntilComplete(
 
 		assert.equal(sent.err, undefined);
 
+		const ids = namedIds(sent.smsIds);
+
 		const complete = await waitFor(() => {
-			const allIntact = sent.smsIds.every(id => dlrLooksIntact(dlrs.find(r => r.dlr.smsId === id)));
+			const allIntact = ids.every(id => dlrLooksIntact(dlrs.find(r => r.dlr.smsId === id)));
 			const reassembled = sms.find(s => s.message === message);
 
 			return allIntact && reassembled ? { reassembled } : undefined;
 		}, DLR_RETRY_BUDGET_MS);
 
-		if (complete) return { reassembled: complete.reassembled, smsIds: sent.smsIds };
+		if (complete) return { reassembled: complete.reassembled, smsIds: ids };
 	}
 
 	throw new Error(`no attempt got both an intact DLR per segment and a loopback reassembly within ${String(DLR_MAX_ATTEMPTS)} tries`);

interop-tests/smscsim.test.ts

@@ -38,13 +38,17 @@ async function sendAndAwaitDlrs(session: Session, dlrs: Dlr[], message: string):
 
 	assert.equal(sent.err, undefined);
 
+	const ids = sent.smsIds.filter(id => id !== undefined);
+
+	assert.equal(ids.length, sent.smsIds.length, 'expected smscsim to name a message id for every segment');
+
 	const complete = await waitFor(() => (
-		sent.smsIds.every(id => dlrs.some(dlr => dlr.smsId === id)) ? true : undefined
+		ids.every(id => dlrs.some(dlr => dlr.smsId === id)) ? true : undefined
 	));
 
 	assert.ok(complete, 'every segment of the first send should get a DLR');
 
-	return sent.smsIds;
+	return ids;
 }
 
 describe('smscsim - C1 bind, keepalive, unbind', () => {