Vetur 0.26.x is no longer applying changes for eslint / prettier

[geoidesic]

• I have searched through existing issues
• I have read through docs
• I have read FAQ

Info

• Platform: macOS
• Vetur version: 0.26.1
• VS Code version: 1.47.3

Problem

Yesterday Vetur was working fine, it would fix my VueJS SFC files on save. I've made no changes to VsCode settings. Today Vetur no longer fixes my code. I've had to roll back to v0.25.0 to get it to work again.

Reproducible Case

The steps are simple in my case: open any SFC VueJS file, write some non-eslint-compliant code and hit save. It should correct the code to eslint standard.

Here is my settings.json:

{
  // "editor.formatOnPaste": true,
  "editor.formatOnSave": true,
  "editor.codeActionsOnSave": {
    "source.fixAll": true
  },
  "jest.pathToJest": "yarn test:unit",
  "jest.showCoverageOnLoad": true,
  "php-cs-fixer.executablePath": "${extensionPath}/php-cs-fixer.phar",
  "php-cs-fixer.lastDownload": 1596197060819,
  "php-cs-fixer.autoFixBySemicolon": true,
  "php-cs-fixer.onsave": true,
  "stylusSupremacy.insertBraces": false,
  "stylusSupremacy.insertSemicolons": false,
  "vetur.format.defaultFormatter.html": "prettyhtml",
  "vetur.format.defaultFormatter.js": "prettier-eslint",
  "vetur.format.scriptInitialIndent": true,
  "vetur.format.styleInitialIndent": true,
  "window.zoomLevel": 0,
  "diffEditor.ignoreTrimWhitespace": true,
  "[vue]": {
    "editor.defaultFormatter": "octref.vetur"
  },
  "[javascript]": {
    "editor.defaultFormatter": "esbenp.prettier-vscode"
  },
  "editor.tabSize": 2,
  "editor.detectIndentation": false,
  "editor.fontFamily": "Fira Code",
  //"Monaco, Fira Code, Menlo, 'Courier New', monospace",
  "editor.fontLigatures": true
}

Seems to relate to #2116, (which the author closed in impatience).

[octref]

Duplicate of #2125.