filenames.map is not a function

[talentlessguy]

When putting

 "content_scripts": [
    {
      "matches": ["*"],
      "js": "content_url.ts"
    }
  ]

inside a manifest.json I get this error:

➜ yarn dev
yarn run v1.21.1
$ parcel -p 3000 --hmr-port 35887 manifest.json
Server running at http://localhost:3000 
🚨  /home/v1rtl/Coding/ext-tracking/manifest.
json: filenames.map is not a function
    at ManifestAsset.processMultipleDependencies (/home/v1rtl/Coding/ext-tracking/node_modules/.pnpm/registry.npmjs.org/parcel-plugin-web-extension/1.6.1/node_modules/parcel-plugin-web-extension/src/ManifestAsset.js:125:26)
    at ManifestAsset.processContentScripts (/home/v1rtl/Coding/ext-tracking/node_modules/.pnpm/registry.npmjs.org/parcel-plugin-web-extension/1.6.1/node_modules/parcel-plugin-web-extension/src/ManifestAsset.js:168:34)

here's my package.json:

{
  "name": "ext-tracking",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "dev": "parcel -p 3000 --hmr-port 35887 manifest.json"
  },
  "keywords": [],
  "author": "v1rtl",
  "license": "ISC",
  "browserslist": [
    "last 1 Chrome versions"
  ],
  "devDependencies": {
    "@types/chrome": "^0.0.104",
    "parcel-bundler": "^1.12.4",
    "parcel-plugin-web-extension": "^1.6.1",
    "typescript": "^3.8.3"
  },
  "dependencies": {
    "htm": "^3.0.4",
    "preact": "^10.4.0"
  }
}

[emschwartz]

The js field should be an array of files rather than the single string content_url.ts