CHANGELOG.md

@@ -39,7 +39,8 @@
   other limits. `server({ maxOctets: 0 })` used to start and then refuse every multipart message.
 - `callback_num`, `callback_num_atag`, `callback_num_pres_ind`, `broadcast_area_identifier` and
   `broadcast_error_status` read as a list of every copy the peer sent, where only the last was kept,
-  and are written from a list. A single value for one of them, or a list for any other tag, is
+  and are written from a list. A single value or an empty list for one of them, or a list for any
+  other tag, is
   refused.
 - `tlvMap` is gone from the `broadcast_sm_resp` command definition. Nothing read it.
 

src/defs/tlvs.ts

@@ -135,7 +135,11 @@ export function tagIdOf(name: string, input: TlvInput): Result<{ tagId: number }
 function copiesOf(name: string, definition: TlvDefinition | undefined, value: TlvValue): Result<{ copies: TlvScalar[] }> {
 	const multiple = definition?.multiple === true;
 
-	if (Array.isArray(value) && multiple) return { copies: value };
+	if (Array.isArray(value) && multiple) {
+		return value.length > 0
+			? { copies: value }
+			: { err: new Error(`TLV "${name}": give at least one value, or leave the tag out`) };
+	}
 
 	if (!Array.isArray(value) && !multiple) return { copies: [value] };
 

test/pdu.test.ts

@@ -432,16 +432,18 @@ describe('TLVs', () => {
 		assert.deepEqual(pduObj.tlvs.callback_num_pres_ind?.tagValue, [1]);
 	});
 
-	test('refuses a single value for a tag SMPP lets repeat, and a list for one it does not', () => {
+	test('refuses a single value or an empty list for a tag SMPP lets repeat, and a list for one it does not', () => {
 		const params = { destination_addr: '46709771337', short_message: 'hi', source_addr: '46701113311' };
 		const single = objToPdu({
 			cmdName: 'submit_sm',
 			params,
 			tlvs: { callback_num: { tagValue: Buffer.from('46701113311', 'latin1') } },
 		});
+		const empty = objToPdu({ cmdName: 'submit_sm', params, tlvs: { callback_num: { tagValue: [] } } });
 		const list = objToPdu({ cmdName: 'submit_sm', params, tlvs: { source_port: { tagValue: [1234] } } });
 
 		assert.match(single.err?.message ?? '', /TLV "callback_num": .*list/);
+		assert.match(empty.err?.message ?? '', /TLV "callback_num": .*leave the tag out/);
 		assert.match(list.err?.message ?? '', /TLV "source_port": .*list/);
 	});