tasks: 'configure tasks' does not work correctly and overrides previously configured tasks

[vince-fugnitto]

Bug Description:

Given that a user attempts to configure more than two tasks, the last task is always overwritten. This behavior is not what is expected, and does not produce the same results compared to vscode.

Theia (after performing multiple configures):

{
  "tasks": [
    {
      "type": "vince",
      "task": "vince-build",
      "problemMatcher": []
    },
    {
      "type": "vince",
      "task": "vince-none",
      "problemMatcher": []
    }
  ]
}

VS Code (after performing multiple configures):

{
  "version": "2.0.0",
  "tasks": [
    {
      "type": "vince",
      "task": "vince-build",
      "group": "build",
      "problemMatcher": [],
      "label": "vince: vince-build"
    },
    {
      "type": "vince",
      "task": "vince-clean",
      "group": "clean",
      "problemMatcher": [],
      "label": "vince: vince-clean"
    },
    {
      "type": "vince",
      "task": "vince-none",
      "problemMatcher": [],
      "label": "vince: vince-none"
    },
    {
      "type": "vince",
      "task": "vince-rebuild",
      "group": "rebuild",
      "problemMatcher": [],
      "label": "vince: vince-rebuild"
    },
    {
      "type": "vince",
      "task": "vince-test",
      "group": "test",
      "problemMatcher": [],
      "label": "vince: vince-test"
    }
  ]
}

With the framework, I'm only ever able to get 2 tasks configured, while in vscode I have all of them.

Steps to Reproduce:

In order to reproduce, I created a custom TaskProvider extension which contributes multiple tasks:

• https://github.com/vince-fugnitto/vscode-task-provider-example

1. add the example vscode-task-provider-example extension to the framework
2. open a workspace (ensure that no .theia or .vscode folder is present in the workspace
3. run the command configure tasks
4. repeat the process for all items in the list (notice that the last configuration always gets overwritten)
5. test the extension in vscode and notice that it does not overwrite pre-existing configurations

Additional Information

• Operating System: Ubuntu 18.04
• Theia Version: 47be972

[msujew]

@vince-fugnitto I've spent some time looking into this one. It seems like the main reasons this happens are:

• Only tasks that are commited to the tasks.json file are actually loaded in the model.
• Newly configured tasks are not written to disc because of this code as the tasks.json editor is open when configuring a second task.

When saving the tasks file in between running the configure tasks command, the intended behaviour emerges.

In vscode changes to the tasks.json file via the configure tasks command are always commited. I'd recommend implementing the same behaviour. I'll try finding a solution myself today.