Possible solution to avoid the need for a temporary .user.js redirect for installation

[tophf]

Currently when installing from sites like greasyfork, Tampermonkey has to redirect to a temporary URL in order to circumvent the lack of proper redirection in ManifestV3, https://github.com/w3c/webextensions/issues/610.

Looks like a better workaround might be to change the content-type header of .user.js URLs to an html page to prevent Chrome's built-in handling, so instead a normal navigation is performed, which will be seen by a non-blocking webRequest or chrome.tabs.onUpdated or chrome.webNavigation.

chrome.declarativeNetRequest.updateSessionRules({
  removeRuleIds: [1],
  addRules: [{
    id: 1,
    condition: {
      urlFilter: '.user.js|',
      resourceTypes: ['main_frame']
    },
    action: {
      type: 'modifyHeaders',
      responseHeaders: [{header:'content-type', value: 'text/html', operation: 'set'}]
    }
  }]
})

This example only shows one pattern in urlFilter. I don't know what's best for multiple patterns, either several identical rules with different urlFilter or one rule with regexFilter.

[derjanb]

Unfortunately this is not a solution because html in userscripts is parsed as such.

[tophf]

It can be prevented by running stop(); in a content script for .user.js at document_start.