# Using done()/complete for debugging

**URL:** <https://discourse.nodered.org/t/using-done-complete-for-debugging/21572>\
**Category:** General\
**Created:** [12 February 2020 00:21 UTC](https://discourse.nodered.org/t/using-done-complete-for-debugging/21572 "2020-02-12T00:21:13Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![drmibell](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/drmibell/32/8424_2.png) [@drmibell](https://discourse.nodered.org/u/drmibell)\
**Post date:** [12 February 2020 00:21 UTC](https://discourse.nodered.org/t/using-done-complete-for-debugging/21572/1 "2020-02-12T00:21:14Z")

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Apologies if this has been mentioned before -- I am further behind than usual in reading the forum.

When possible, I avoid using global variables by attaching state information to each message. I recently built a flow with some complex logic that was not producing the messages I expected in certain cases. Using a `complete` node attached to a `debug` node, I could catch the messages as they passed through each `function` and `change` node in the flow and so was able to see each message as it was modified at various points and find the problem.

This flow gives the general idea:

```auto
[{"id":"618b1cf1.6df17c","type":"inject","z":"42e9cb90.fa9734","name":"inject","topic":"testing complete node","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":110,"y":280,"wires":[["d6ea6b13.304ce8","ed2f9d3d.1bcef8"]]},{"id":"17d0a463.499f2c","type":"debug","z":"42e9cb90.fa9734","name":"function output","active":false,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":460,"y":260,"wires":[]},{"id":"fa3c7acb.30e618","type":"complete","z":"42e9cb90.fa9734","name":"","scope":["d6ea6b13.304ce8","ed2f9d3d.1bcef8"],"uncaught":false,"x":110,"y":360,"wires":[["1d04b428.2c777c"]]},{"id":"1d04b428.2c777c","type":"debug","z":"42e9cb90.fa9734","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":250,"y":360,"wires":[]},{"id":"d6ea6b13.304ce8","type":"change","z":"42e9cb90.fa9734","name":"","rules":[{"t":"set","p":"time","pt":"msg","to":"payload","tot":"msg"},{"t":"set","p":"payload","pt":"msg","to":"topic","tot":"msg"},{"t":"set","p":"foo","pt":"msg","to":"bar","tot":"str"},{"t":"set","p":"topic","pt":"msg","to":"change node output","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":280,"y":300,"wires":[["c90a3799.49fe6"]]},{"id":"ed2f9d3d.1bcef8","type":"function","z":"42e9cb90.fa9734","name":"dummy function","func":"\nreturn msg;","outputs":1,"noerr":0,"x":280,"y":260,"wires":[["17d0a463.499f2c"]]},{"id":"c90a3799.49fe6","type":"debug","z":"42e9cb90.fa9734","name":"change output","active":false,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":460,"y":300,"wires":[]}]

```

Before making a habit of this, I have a few questions:

- Are there obvious down sides to using `complete` as a debugging tool in this way?
- Is this behavior likely to change in the future?
- Are there core nodes in addition to `function`, `change`, and `debug` that have implemented the `done()` function?
- Would it be possible to add `done()` to other core nodes that transmit messages, like `link`, `delay`, and `trigger`, or that generate messages like `inject`, `range` and `random`?

Also, a couple of observations, illustrated by this flow:

```auto
[{"id":"c39db174.4b3d2","type":"complete","z":"f953caa6.ca00c","name":"","scope":["119e8e79.9e8012","171cafbb.ddde5","b1af9e2c.05fcc8"],"uncaught":false,"x":150,"y":240,"wires":[["8b9484f6.1ad448"]]},{"id":"5a2dbdb6.575ee4","type":"inject","z":"f953caa6.ca00c","name":"","topic":"empty function and debug","payload":"hello world","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":140,"y":140,"wires":[["171cafbb.ddde5","119e8e79.9e8012","b1af9e2c.05fcc8"]]},{"id":"119e8e79.9e8012","type":"debug","z":"f953caa6.ca00c","name":"empty debug","active":false,"tosidebar":false,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","x":310,"y":140,"wires":[]},{"id":"171cafbb.ddde5","type":"function","z":"f953caa6.ca00c","name":"empty function","func":"","outputs":0,"noerr":0,"x":320,"y":100,"wires":[]},{"id":"8b9484f6.1ad448","type":"debug","z":"f953caa6.ca00c","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","x":290,"y":240,"wires":[]},{"id":"b1af9e2c.05fcc8","type":"function","z":"f953caa6.ca00c","name":"function (no output)","func":"msg.payload = \"goodbye world\"\nmsg.topic = \"not empty function\"\nmsg.foo = \"bar\"","outputs":0,"noerr":0,"x":330,"y":180,"wires":[]}]

```

- Both the `function` and `debug` nodes will send a message to the `complete` node even when they do nothing to the input message and have no output.
- The function node can modify the message sent to the `complete` node even when it has no output.
- If the `complete` node is allowed to catch output from its attached `debug` node, you get a loop. 😉

---

<div class="post-metadata">

**Author:** ![kuema](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/kuema/32/6542_2.png) [@kuema](https://discourse.nodered.org/u/kuema)\
**Post date:** [12 February 2020 06:58 UTC](https://discourse.nodered.org/t/using-done-complete-for-debugging/21572/2 "2020-02-12T06:58:40Z")

</div>

That's a nice use-case for the complete node! 🙂

> [@drmibell](#):
>
> Are there core nodes in addition to `function` , `change` , and `debug` that have implemented the `done()` function?

There's a pending pull request for the remaining core nodes. [Messaging API support of core nodes by k-toumura · Pull Request #2402 · node-red/node-red · GitHub](https://github.com/node-red/node-red/pull/2402)

> [@drmibell](#):
>
> Would it be possible to add `done()` to other core nodes that transmit messages, like `link` , `delay` , and `trigger` , or that generate messages like `inject` , `range` and `random` ?

The `done()` callback is only available in nodes that handle incoming messages to signal completion. So it wouldn't make much sense for nodes without an input port, like `inject`.

> [@drmibell](#):
>
> Are there obvious down sides to using `complete` as a debugging tool in this way?

My question for this to work would be: Is the `complete` node notified **before** the message is passed to the next nodes? So the message that arrived in the debug bar is still the same and not yet modified by following nodes. Once it was sent to the editor it doesn't matter if it's been modified.  
The runtime is another subject, the message could have been modified if it hasn't been cloned by the `complete` node (not sure if it does).

---

<div class="post-metadata">

**Author:** ![drmibell](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/drmibell/32/8424_2.png) [@drmibell](https://discourse.nodered.org/u/drmibell)\
**Post date:** [20 February 2020 19:43 UTC](https://discourse.nodered.org/t/using-done-complete-for-debugging/21572/3 "2020-02-20T19:43:53Z")

</div>

> [@kuema](#):
>
> Is the `complete` node notified **before** the message is passed to the next nodes?

Thanks for your comments. I wish I could answer that question with certainty by examining the code, but the message-passing internals of NR are beyond my grasp. (I once tried to sort out something similar for the `link` node and failed miserably.) Experimentally, I have tried a number of flows, both linear and branching, that change the message at each step, and have not run into any problems. YMMV.

---

<div class="post-metadata">

**Author:** ![kuema](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/kuema/32/6542_2.png) [@kuema](https://discourse.nodered.org/u/kuema)\
**Post date:** [21 February 2020 05:41 UTC](https://discourse.nodered.org/t/using-done-complete-for-debugging/21572/4 "2020-02-21T05:41:44Z")

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I couldn't get how the link nodes work either. Maybe there is some more special internal handling involved. I saw that it uses `RED.events`, so I guess it uses the runtime events to work.

> [@drmibell](#):
>
> Experimentally, I have tried a number of flows, both linear and branching, that change the message at each step, and have not run into any problems.

Well, that behaviour would make sense in terms of life-cycle.

I tried digging through the code multiple times, but I ended up stopping that due to time constraints. At work I am just a one-man team who does the platform development. So most of the time goes there, our custom nodes and keeping up-to-date. And at home there are other commitments besides the personal projects (including Node-RED). 🙂

Though I'd like to know more about the runtime, and to make contributions at some time, time is the limiting factor. 😧

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [21 April 2020 05:45 UTC](https://discourse.nodered.org/t/using-done-complete-for-debugging/21572/5 "2020-04-21T05:45:34Z")

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