Unhandled exeption for variable named "error"

[bergmanu]

Describe the bug

If a variable in the s7 node is named "error", node-red crashes with unhandled exepction in the following cases:

1. using single variable -> error with uncheckd "Emit only when value changes (diff)"
2. using All variables with checked and unchecked "Emit only when value changes (diff)"
3. using All variables, one per message with checked and unchecked "Emit only when value changes (diff)"

Whereas it doesn't crash using single variable -> error with checked "Emit only when value changes (diff)"

To Reproduce

For reproducing you need a PLC with DB1. It contains in my example the variables in the screenshot

node-red only crashes if it can successfully connect to PLC.

Steps to reproduce the behavior:

1. Import attached flow
2. Deploy -> everything works
3. Rename variable "test" to "error"
4. Deploy -> still works
5. uncheck "Emit only when value changes (diff)" for the error variable
6. Deploy -> node-red crashes

Expected behavior

The s7 node reads out the variables in any case, it shouldn't matter how they are named

Logs

14 May 08:30:39 - [red] Uncaught Exception:
14 May 08:30:39 - Error [ERR_UNHANDLED_ERROR]: Unhandled error. (true)
    at S7Endpoint.emit (events.js:187:17)
    at S7Endpoint.Node.emit (/usr/lib/node_modules/node-red/node_modules/@node-red/runtime/lib/nodes/Node.js:185:20)
    at /home/root/.node-red/node_modules/node-red-contrib-s7/red/s7.js:343:26
    at Array.forEach (<anonymous>)
    at NodeS7.cycleCallback [as readDoneCallback] (/home/root/.node-red/node_modules/node-red-contrib-s7/red/s7.js:340:33)
    at NodeS7.readResponse (/home/root/.node-red/node_modules/nodes7/nodeS7.js:1447:9)
    at NodeS7.onResponse (/home/root/.node-red/node_modules/nodes7/nodeS7.js:1243:9)
    at Socket.<anonymous> (/home/root/.node-red/node_modules/nodes7/nodeS7.js:418:20)
    at Socket.emit (events.js:198:13)
    at addChunk (_stream_readable.js:288:12)
node-red.service: Main process exited, code=exited, status=1/FAILURE
node-red.service: Failed with result 'exit-code'

Flow

[{"id":"74a983bd.c83efc","type":"s7 in","z":"f8907b7a.5fd9e8","endpoint":"6f2223c.71411dc","mode":"single","variable":"status","diff":true,"name":"","x":150,"y":100,"wires":[[]]},{"id":"a085508f.6f5ca","type":"s7 in","z":"f8907b7a.5fd9e8","endpoint":"6f2223c.71411dc","mode":"single","variable":"statusID","diff":true,"name":"","x":160,"y":160,"wires":[[]]},{"id":"82995af9.3f7168","type":"s7 in","z":"f8907b7a.5fd9e8","endpoint":"6f2223c.71411dc","mode":"single","variable":"bool1","diff":true,"name":"","x":150,"y":220,"wires":[[]]},{"id":"5b686495.d97afc","type":"s7 in","z":"f8907b7a.5fd9e8","endpoint":"6f2223c.71411dc","mode":"single","variable":"test","diff":true,"name":"","x":150,"y":280,"wires":[[]]},{"id":"f2c93088.6b76","type":"s7 in","z":"f8907b7a.5fd9e8","endpoint":"6f2223c.71411dc","mode":"single","variable":"bool2","diff":true,"name":"","x":150,"y":340,"wires":[[]]},{"id":"6f2223c.71411dc","type":"s7 endpoint","z":"","transport":"iso-on-tcp","address":"192.168.200.60","port":"102","rack":"0","slot":"1","localtsaphi":"01","localtsaplo":"00","remotetsaphi":"01","remotetsaplo":"00","connmode":"rack-slot","adapterauto":true,"adapterport":"","busaddr":"2","adapteraddr":"0","cycletime":"500","timeout":"1500","verbose":"default","name":"","vartable":[{"addr":"DB1,WORD0","name":"status"},{"addr":"DB1,INT2","name":"statusID"},{"addr":"DB1,X4.0","name":"bool1"},{"addr":"DB1,X4.1","name":"test"},{"addr":"DB1,X4.2","name":"bool2"}]}]

Environment

• Version of this node: 2.1.1
• Node-RED version: 1.0.2
• PLC Part Number: PLCSim Advanced V3.0 (with S7-1515-2 PN)
• OS for node-red: Debian 10 on Siemens IOT2050 (https://github.com/siemens/meta-iot2050)
• OS for Browser: Windows 10
• Browser: Chrome

[gfcittolin]

This variable name is indeed not supported because it's a reserved event name on Node.JS. There is also other internal reserved names like __ALL__, __CHANGED__, __ALL_CHANGED__ and __STATUS__.