support modifying existing problem matchers

[elaihau]

• VS Code supports the possibility of modifying existing problem matchers. With this change, Theia users can define a base problem matcher in which they can further customize the properties fileLocation, applyTo, owner, severity, pattern, and source.

• resolves [tasks] support modifying existing problem matchers #6427

Signed-off-by: Liang Huang [email protected]

How to test

With this change, a user can define a base problem matcher in which they can further customize:

{
  "type": "npm",
  "script": "lint",
  "problemMatcher": {
    "base": "$eslint-stylish",
    "applyTo": "closedDocuments"
  },
  "isBackground": true
}

Instead of linting all files, the task above only lints the closed documents due to the existence of "applyTo": "closedDocuments"

Steps to test

1. Open a workspace, define a task that produces warnings ONLY.
   Mine is

    {
        "type": "npm",
        "script": "lintAAB",
        "problemMatcher": [
            "$eslint-stylish"
            ]
          }
        ]
    }

and the npm lintAAB is defined in package.json as follows

  "scripts": {
    "lintAAB": "eslint ."
  }

2. Run the task. After the task finishes, all warnings should have been displayed as warning markers in the problems view.

3. Use "$eslint-stylish" as the base, and override the patterns property. The task config looks like this:

        {
            "type": "npm",
            "script": "lintAAB",
            "problemMatcher": [{
                "base": "$eslint-stylish",
                "pattern": [
                        {
                            "regexp": "^([^\\s].*)$",
                            "kind": "location",
                            "file": 1
                        },
                        {
                            "regexp": "^\\s+(\\d+):(\\d+)\\s+(error|warning|info)\\s+(.+?)(?:\\s\\s+(.*))?$",
                            "line": 1,
                            "column": 2,
                            "severity": 1, // error
                            "message": 4,
                            "code": 5,
                            "loop": true
                        }
                    ]
            }   
            ]
        }

4. Run this task one more time, check the problems view after it finishes
   Expected: all warning markers are created as error markers this time

5. Repeat Step 1 - 4 for other properties, such as fileLocation, applyTo, owner, severity, pattern, and source.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

[vince-fugnitto]

I verified the changes using a modified version of my workspace eslint-ws, and was able to successfully extend eslint-stylish by updating properties. 👍

For example, I was able to modify:

• severity
• applyTo
• owner
• source
• pattern
• fileLocation