Terminal output is truncated

[sguillia]

Issue Type: Bug

Please have a look at this screenshot

The program is supposed to print a lot of lines (all letter combinations from a to z).

Bug: The terminal output gets truncated randomly, about one time out of five.

4 times out of 5, there is no problem, I can see the last line, in this case the one with z z z.

Here is another screenshot.

I added this in tasks.json so it is normal not to have the Terminal will be reused by tasks, press any key to close it. at the end.

    "presentation": {
        "showReuseMessage": false
    }

To prove it is a display or buffering problem, and not my task getting stopped, I have changed the code so that it writes text to a file at the very end of the program.

When I took the screenshot, the file tmp/vscode-bug-demo.txt existed and had the text inside it.

Here is the content of tasks.json:

{
	// See https://go.microsoft.com/fwlink/?LinkId=733558
	// for the documentation about the tasks.json format
	"version": "2.0.0",
	"tasks": [
		{
			"label": "Bug demo",
			"type": "shell",
			"command": "python3 print-a-lot-of-lines.py",
			"group": {
				"kind": "build",
				"isDefault": true
			}
		}
	],
    "presentation": {
        "showReuseMessage": false
    }
}

(btw your template is not a valid JSON file because of the comments)

Here is the Python 3 code if you want to try to reproduce:

#!/usr/bin/python3

for x in range(ord('a'), ord('z')+1):
	for y in range(ord('a'), ord('z')+1):
		for z in range(ord('a'), ord('z')+1):
			print("Bad combination: " + chr(x) + ' ' + chr(y) + ' ' + chr(z))

# Prove that the task has not been interrupted 
with open("/tmp/vscode-bug-demo.txt", "a") as myfile:
    myfile.write("Task has run until the end")

I have another program in Go, that does the same thing (printing all combinations of three letters from a to z). The terminal output is truncated most of the time which makes the terminal output, and consequently the task system, useless. I wrote the python example in order to reproduce the bug with a simple program.

Steps to Reproduce:

1. Have a program that prints a lot of lines (17576 in my case and if often stops near the end)
2. Have a task so that the program output goes in Terminal output
3. Play the build shortcut several times (wait until previous task is done before launching again)
4. Observe as the terminal output gets truncated

---

VS Code version: Code 1.35.0 (553cfb2, 2019-06-04T01:13:26.790Z)
OS version: Linux x64 4.15.0-51-generic

System Info

Item	Value
CPUs	Intel(R) Core(TM) i5-8300H CPU @ 2.30GHz (8 x 3900)
GPU Status	2d_canvas: enabled checker_imaging: disabled_off flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software rasterization: disabled_software surface_synchronization: enabled_on video_decode: unavailable_off webgl: enabled webgl2: enabled
Load (avg)	1, 1, 1
Memory (System)	7.64GB (2.64GB free)
Process Argv	--unity-launch
Screen Reader	no
VM	0%

Extensions: none

[Tyriar]

/duplicate #38137