fix: discard unprocessed lines/data when connection connects/disconnects

If there is any data there, it will be incomplete, with the remainder lost due to the broken connection

src/__tests__/connection.spec.ts

@@ -367,7 +367,7 @@ describe('connection', () => {
 			}
 		})
 
-		it('test with full connection', async () => {
+		it('test with full client', async () => {
 			const client = new BasicCasparCGAPI({
 				host: '127.0.0.1',
 				port: 5250,
@@ -458,5 +458,103 @@ describe('connection', () => {
 				client.disconnect()
 			}
 		})
+
+		it('connection loss midway through response', async () => {
+			const conn = new Connection('127.0.0.1', 5250, true)
+			try {
+				expect(conn).toBeTruthy()
+
+				const onConnError = jest.fn()
+				const onConnData = jest.fn()
+				conn.on('error', onConnError)
+				conn.on('data', onConnData)
+
+				const sockets = SocketMock.openSockets()
+				expect(sockets).toHaveLength(1)
+
+				// Dispatch a command
+				const sendError = await conn.sendCommand(
+					{
+						command: Commands.Info,
+						params: {},
+					},
+					'cmd1'
+				)
+				expect(sendError).toBeFalsy()
+				expect(onConnError).toHaveBeenCalledTimes(0)
+				expect(onConnData).toHaveBeenCalledTimes(0)
+
+				// Info was sent
+				expect(onSocketWrite).toHaveBeenCalledTimes(1)
+				expect(onSocketWrite).toHaveBeenNthCalledWith(1, 'REQ cmd1 INFO\r\n', 'utf-8')
+				// expect(onSocketWrite).toHaveBeenNthCalledWith(2, 'REQ cmd2 PLAY 1-10\r\n', 'utf-8')
+				onSocketWrite.mockClear()
+
+				// Reply with a part of a fragmented message
+				sockets[0].mockData(Buffer.from(`RES cmd1 201 INFO OK\r\n<?xml`))
+				await new Promise(setImmediate)
+
+				expect(conn.connected).toBeTruthy()
+				expect(onConnError).toHaveBeenCalledTimes(0)
+				expect(onConnData).toHaveBeenCalledTimes(0)
+
+				// Simulate connection failure
+				sockets[0].emit('close', new Error('Connection lost'))
+				await new Promise(setImmediate)
+
+				expect(conn.connected).toBeFalsy()
+				expect(onConnError).toHaveBeenCalledTimes(0)
+				expect(onConnData).toHaveBeenCalledTimes(0)
+
+				// Reconnect
+				sockets[0].emit('connect')
+				await new Promise(setImmediate)
+
+				expect(conn.connected).toBeTruthy()
+				expect(onConnError).toHaveBeenCalledTimes(0)
+				expect(onConnData).toHaveBeenCalledTimes(0)
+
+				// Send a command in the new connection
+				const sendError2 = await conn.sendCommand(
+					{
+						command: Commands.Play,
+						params: {
+							channel: 1,
+							layer: 10,
+						},
+					},
+					'cmd2'
+				)
+				expect(sendError2).toBeFalsy()
+
+				// Check was sent
+				expect(onSocketWrite).toHaveBeenCalledTimes(1)
+				expect(onSocketWrite).toHaveBeenNthCalledWith(1, 'REQ cmd2 PLAY 1-10\r\n', 'utf-8')
+
+				await new Promise(setImmediate)
+				expect(onConnError).toHaveBeenCalledTimes(0)
+				expect(onConnData).toHaveBeenCalledTimes(0)
+
+				// Reply with successful PLAY
+				sockets[0].mockData(Buffer.from(`RES cmd2 202 PLAY OK\r\n`))
+				await new Promise(setImmediate)
+
+				expect(onConnError).toHaveBeenCalledTimes(0)
+				expect(onConnData).toHaveBeenCalledTimes(1)
+
+				// Check result looks good
+				expect(onConnData).toHaveBeenNthCalledWith(1, {
+					command: 'PLAY',
+					data: [],
+					message: 'The command has been executed.',
+					reqId: 'cmd2',
+					responseCode: 202,
+					type: 'OK',
+				})
+			} finally {
+				// Ensure cleaned up
+				conn.disconnect()
+			}
+		})
 	})
 })

src/connection.ts

@@ -231,12 +231,19 @@ export class Connection extends EventEmitter<ConnectionEvents> {
 		})
 		this._socket.on('connect', () => {
 			this._setConnected(true)
+
+			// Any data which hasn't been parsed yet is now incomplete, and can be discarded
+			this._discardUnprocessed()
 		})
 		this._socket.on('close', () => {
+			this._discardUnprocessed()
+
 			this._setConnected(false)
 			this._triggerReconnect()
 		})
 		this._socket.on('error', (e) => {
+			this._discardUnprocessed()
+
 			if (`${e}`.match(/ECONNREFUSED/)) {
 				// Unable to connect, no need to handle this error
 				this._setConnected(false)
@@ -248,6 +255,11 @@ export class Connection extends EventEmitter<ConnectionEvents> {
 		this._socket.connect(this.port, this.host)
 	}
 
+	private _discardUnprocessed() {
+		this._unprocessedData = ''
+		this._unprocessedLines = []
+	}
+
 	private _setConnected(connected: boolean) {
 		if (connected) {
 			if (!this._connected) {