Uncaught TypeError When Calling Bunch of ``echo`` in a Loop

[KiddoV]

Issue summary

I am just printing a bunch of strings line by line to the terminal using echo and got into this error every time:

null:10460  Uncaught TypeError: Cannot read properties of undefined (reading 'length')
    at null:10460:59
    at FormatBuffer.forEach (null:1976:17)
    at FormatBuffer.flush (null:1982:14)
    at ready (null:10414:32)
    at DelayQueue.add (null:256:17)
    at null:9364:23
    at jQuery.fn.init.flush (null:10395:17)
    at jQuery.fn.init.flush (null:11486:32)
    at null:10781:42
    at unpromise (null:1136:20)

It is pointing to this line number 10460 (line 10390 in the source code) =>

jquery.terminal/js/jquery.terminal.js

Line 10390 in ef9b638

snapshot[snapshot.length - 1] += data.raw;

I don't think I can re-produce this error. But you can check out the Gif below

Noted: all the white colored string characters come from a serial COM port.
The weird thing is this error ONLY occurs on the 18th index of the for loop.
This error cause the terminal to stop receiving data from the echo method until I type clear in the terminal then everything works again.

I was hoping you can give me some ideas why is the snapshot was undefined at that point, so I can track down what causing this in my end.

Thanks,

[jcubic]

Can you just save the output into a file as a JSON array and send the file? You can also make things easier to remove the COM port from the equation. Just write a simple demo that read the same stuff from a file.

Also, you can try to reproduce the same by adding a bunch of echo yourself in the code (the same that was done by the COM port). It will be easier to debug if I have something that reproduces the issue.

[jcubic]

I would just try to write code that connect to COM and just use:

const output = [];

// save all lines here:
output.push(com_line);

console.log(output);

You will see what is the output and you will be able to reproduce the error for instance on CodePen.

The reason why it's better than saving into a file, because you can have undefined values, that may be in the output. If all are text you can save them into a file, or just write or just embed the JSON into the demo.

[KiddoV]

So do you think that the COM serial sending some weird characters that causing this issue?

[jcubic]

I need to see the array of strings you're using. This have probably nothing to do with COM port only the specific sequence of lines. To be able to debug this I need to see what you're sending to the terminal and what code you use.

[jcubic]

I expect that you use echo(xxxx, { newline: false }); that is causing this issue. This is a feature that was added by one contributor and I'm fixing the issue since the feature was introduced. Don't get me wrong I'm glad the feature was added but it took a while before it was usable. And I'm not sure if it works correctly with typing animation.

[KiddoV]

This is all the string I got from COM port and sending it to the terminal in a loop:

at

OK

att
Command not found!

ERROR

ati
MultiTech xDot
Firmware : 4.1.5-debug-mbed60800
Library  : 4.1.3-debug-mbed60800
MTS-Lora : 4.1.3-debug-mbed60800

OK

at+di?
00-80-00-00-00-ff-ff-ff

OK

Also all characters in bytes...

[97][116 13 13 10 13 10 79 75 13 10 13 13 10][97][116 116 13 13 10][67][111 109 109 97 110 100 32 110 111 116 32 102 111 117 110 100 33 13 10 13 10 69 82 82 79 82 13 10 13 13 10][97][116 105 13 13 10 77 117 108 116 105 84 101 99 104 32 120 68 111 116 13 10 70 105 114 109 119 97 114 101 32 58 32 52 46 49 46 53 45 100 101 98 117 103 45 109 98 101 100 54 48 56 48 48 13 10 76 105 98 114 97 114 121][32][32 58 32 52 46 49 46 51 45 100 101 98 117 103 45 109 98 101 100 54 48 56 48 48 13 10 77 84 83 45 76 111 114 97 32 58 32 52 46 49 46 51 45 100 101 98 117 103 45 109 98 101 100 54 48 56 48 48 13 10 13 10][79][75 13 10 13 13 10][97][116 43 100 105 63 13 13 10][48][48 45 56 48 45 48 48 45 48 48 45 48 48 45 102 102 45 102 102 45 102 102 13 10 13 10 79 75 13 10 13 13 10]

Noted 97 -> a, 116 -> t, 13 -> \n and so on...

---

I expect that you use echo(xxxx, { newline: false });

You are correct, I am using option newline: false because I am expecting newline characters come from the COM port, so I have to turn that off (false).
I tried using echo without that option, and it works.

[jcubic]

OK will try to decode your string of numbers into something usable. Will create a reproduction of the issue, I don't understand why you can't do that yourself.

[jcubic]

Is this correct? https://codepen.io/jcubic/pen/ExdWgqY?editors=1010 I don't see any errors.

Again, please create a reproduction of the error. I can't debug your vague description.

[KiddoV]

I don't understand why you can't do that yourself.

It is because the app is not entirely created from just TypeScript/JavaScript. The string (already converted from bytes) is sent from the backend using Golang to the frontend though WebSocket, and the Golang method is called from a separate thread.

Also, those string come out in an order like this:

//Echo this
[97][116 13 13 10 13 10 79 75 13 10 13 13 10]
//Wait 500 milliseconds

//Echo this
[97][116 116 13 13 10][67][111 109 109 97 110 100 32 110 111 116 32 102 111 117 110 100 33 13 10 13 10 69 82 82 79 82 13 10 13 13 10]
//Wait 500 milliseconds

//Echo this
[97][116 105 13 13 10 77 117 108 116 105 84 101 99 104 32 120 68 111 116 13 10 70 105 114 109 119 97 114 101 32 58 32 52 46 49 46 53 45 100 101 98 117 103 45 109 98 101 100 54 48 56 48 48 13 10 76 105 98 114 97 114 121][32][32 58 32 52 46 49 46 51 45 100 101 98 117 103 45 109 98 101 100 54 48 56 48 48 13 10 77 84 83 45 76 111 114 97 32 58 32 52 46 49 46 51 45 100 101 98 117 103 45 109 98 101 100 54 48 56 48 48 13 10 13 10][79][75 13 10 13 13 10]
//Wait 500 milliseconds

//Echo this
[48][48 45 56 48 45 48 48 45 48 48 45 48 48 45 102 102 45 102 102 45 102 102 13 10 13 10 79 75 13 10 13 13 10]

//Repeat...

Repeat 20 times. The error will usually occurs at index 18th.

So... It will be complicated to re-produce this error for just using TS/JS.

https://codepen.io/kiddov/pen/xxyqRLO?editors=1010

[jcubic]

I don't see any error in your codepen demo. The backend doesn't matter the problem is on the frontend, if you have a sequence of lines that you echo you only need to save that somehow. You have to send something else. The gif in the first post has colors, that are missing on your bytes sequence.

Maybe try to publish your code somewhere so I can see the error. If I don't see the error I can help you.

[jcubic]

If you can't provide reproduction can you at least provide full application that I can test?

[KiddoV]

This actually the app I commented here: #849 (comment)
But I don't think you can run it because it required a serial COM port device, which you don't have.

I will find a way to re-produce this 🤔

[jcubic]

I've found a bug in the code that uses the snapshot variable inside the flush method. If you still working on your app you can give it a try with devel version of the library.

If that doesn't help it may require debugging the library itself and finding the root cause of the issue. Unless you will be able to provide a reproduction of the issue.