errors in dependsOn background tasks do not prevent subsequent tasks from executing

• VSCode Version: 1.32.1
• OS Version: 18309

Steps to Reproduce:

create launch.json:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [        
        {
            "type": "chrome",
            "request": "launch",
            "name": "Launch Chrome against localhost",
            "url": "http://localhost:8080",
            "webRoot": "${workspaceFolder}\\src\\FrontEnd\\build",
            "preLaunchTask": "core"
        }
    ]
}

1. create task.json:

{
    // See https://go.microsoft.com/fwlink/?LinkId=733558 
    // for the documentation about the tasks.json format
    "version": "2.0.0",
    "tasks": [
        {
            "label": "core",            
            "type": "npm",
            "script": "start",
            "path": "src/FrontEnd/core/",
            "isBackground": true,
            "dependsOn":["loss"],
            "problemMatcher":{
                "owner": "custom",
                "pattern":[
                    {
                        "regexp": "something not exists",
                        "file": 1,
                        "location": 2,
                        "message": 3
                    }
                ],
                "background": {
                    "activeOnStart": true,
                    "beginsPattern": "core@1.0.0 start",
                    "endsPattern": "created ..\\\\build\\\\vendor.js"
                }
            }
        },
        {
            "label": "loss",            
            "type": "npm",
            "script": "watch",
            "path": "src/FrontEnd/loss/",
            "isBackground": true,            
            "problemMatcher":{
                "owner": "custom",
                "pattern":[
                    {
                        "regexp": "something not exists",
                        "file": 1,
                        "location": 2,
                        "message": 3
                    }
                ],
                "background": {
                    "activeOnStart": true,
                    "beginsPattern": "loss@1.0.0 start",
                    "endsPattern": "waiting for changes"
                }
            }
        }
    ]
}

I can use beginsPattern/endsPattern with no issue if I direct launched by preLaunchTask, but if I have DependsOn for same task, it will run the dependencies but can’t detect it’s status by using endsPattern, the task will hang there. it looks like a bug for me.

I tried to use the new Terminal: “terminal.integrated.windowsEnableConpty”: false/true, no difference. I tried to use presentation.panel:“dedicated”, no difference.

I think we have done a nice work on putting tasks running in background and launch, but not those tasks in DependsOn property.

Does this issue occur when all extensions are disabled?: Yes

[alexr00]

@penx thanks for the simple repro repository.

Until now, you could have background tasks in dependsOn, but since those background tasks never “finish”, you couldn’t sequence anything off of them.

I have pushed a small change that does allow some sequencing. You can have background tasks in dependsOn and they can be sequenced. However any errors that those background tasks produce will not prevent subsequent tasks from executing. I will leave this issue open to track supporting that.

[penx]

I created a basic repo that shows the issue of not being able to create a task that depends on a background/watch task:

https://github.com/penx/vscode-task-dependson

In this project:

• the launch configuration depends on task ‘Two’ and works fine
• the task ‘One’ depends on task ‘Two’ and ‘Three’ in sequence, but neither ‘One’ nor ‘Three’ execute

As per @linusbrolin’s comment above, the documentation says that this should work:

Any background/watch tasks used in dependsOn with “dependsOrder”: “sequence” must have a problem matcher that tracks when they are “done”

… so please can you either mark this ticket as a bug or else update the documentation to make it clear this is not supported?

launch.json

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Node",
      "type": "node",
      "request": "launch",
      "program": "${file}",
      "preLaunchTask": "Two"
    }
  ]
}

tasks.json

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "One",
      "type": "shell",
      "command": "echo start1",
      "dependsOrder": "sequence",
      "dependsOn": ["Two", "Three"],
      "problemMatcher": []
    },
    {
      "label": "Two",
      "type": "shell",
      "isBackground": true,
      "command": "echo start2 && echo end2 && read varname",
      "problemMatcher": {
        "owner": "custom",
        "pattern": {
          "regexp": "^$"
        },
        "background": {
          "activeOnStart": true,
          "beginsPattern": "start2",
          "endsPattern": "end2"
        }
      }
    },
    {
      "label": "Three",
      "type": "shell",
      "command": "echo start3"
    }
  ]
}