Improve no-xhr-if scriptlet

Related issue:
uBlockOrigin/uBlock-issues#2518

assets/resources/scriptlets.js

@@ -2351,26 +2351,34 @@ function noXhrIf(
  const propNeedles = parsePropertiesToMatch(propsToMatch, 'url');
  const log = propNeedles.size === 0 ? console.log.bind(console) : undefined;
  const warOrigin = scriptletGlobals.get('warOrigin');
+ const headers = {
+ 'date': '',
+ 'content-type': '',
+ 'content-length': '',
+ };
  self.XMLHttpRequest = class extends self.XMLHttpRequest {
  open(method, url, ...args) {
  if ( log !== undefined ) {
  log(`uBO: xhr.open(${method}, ${url}, ${args.join(', ')})`);
  return super.open(method, url, ...args);
  }
+ xhrInstances.delete(this);
  if ( warOrigin !== undefined && url.startsWith(warOrigin) ) {
  return super.open(method, url, ...args);
  }
  const haystack = { method, url };
  if ( matchObjectProperties(propNeedles, haystack) ) {
  xhrInstances.set(this, haystack);
  }
+ haystack.headers = Object.assign({}, headers);
  return super.open(method, url, ...args);
  }
  send(...args) {
  const haystack = xhrInstances.get(this);
  if ( haystack === undefined ) {
  return super.send(...args);
  }
+ haystack.headers['date'] = (new Date()).toUTCString();
  let promise = Promise.resolve({
  xhr: this,
  directive,
@@ -2385,53 +2393,81 @@ function noXhrIf(
  },
  });
  switch ( this.responseType ) {
- case 'arraybuffer':
- promise = promise.then(details => {
- details.props.response.value = new ArrayBuffer(0);
- return details;
- });
- break;
- case 'blob':
- promise = promise.then(details => {
- details.props.response.value = new Blob([]);
- return details;
- });
- break;
- case 'document': {
- promise = promise.then(details => {
- const parser = new DOMParser();
- const doc = parser.parseFromString('', 'text/html');
- details.props.response.value = doc;
- details.props.responseXML.value = doc;
- return details;
- });
- break;
- }
- case 'json':
- promise = promise.then(details => {
- details.props.response.value = {};
- details.props.responseText.value = '{}';
+ case 'arraybuffer':
+ promise = promise.then(details => {
+ details.props.response.value = new ArrayBuffer(0);
+ return details;
+ });
+ haystack.headers['content-type'] = 'application/octet-stream';
+ break;
+ case 'blob':
+ promise = promise.then(details => {
+ details.props.response.value = new Blob([]);
+ return details;
+ });
+ haystack.headers['content-type'] = 'application/octet-stream';
+ break;
+ case 'document': {
+ promise = promise.then(details => {
+ const parser = new DOMParser();
+ const doc = parser.parseFromString('', 'text/html');
+ details.props.response.value = doc;
+ details.props.responseXML.value = doc;
+ return details;
+ });
+ haystack.headers['content-type'] = 'text/html';
+ break;
+ }
+ case 'json':
+ promise = promise.then(details => {
+ details.props.response.value = {};
+ details.props.responseText.value = '{}';
+ return details;
+ });
+ haystack.headers['content-type'] = 'application/json';
+ break;
+ default:
+ if ( directive === '' ) { break; }
+ promise = promise.then(details => {
+ return generateContentFn(details.directive).then(text => {
+ details.props.response.value = text;
+ details.props.responseText.value = text;
  return details;
  });
- break;
- default:
- if ( directive === '' ) { break; }
- promise = promise.then(details => {
- return generateContentFn(details.directive).then(text => {
- details.props.response.value = text;
- details.props.responseText.value = text;
- return details;
- });
- });
- break;
+ });
+ haystack.headers['content-type'] = 'text/plain';
+ break;
  }
  promise.then(details => {
+ haystack.headers['content-length'] = `${details.props.response.value}`.length;
  Object.defineProperties(details.xhr, details.props);
  details.xhr.dispatchEvent(new Event('readystatechange'));
  details.xhr.dispatchEvent(new Event('load'));
  details.xhr.dispatchEvent(new Event('loadend'));
  });
  }
+ getResponseHeader(headerName) {
+ const haystack = xhrInstances.get(this);
+ if ( haystack === undefined || this.readyState < this.HEADERS_RECEIVED ) {
+ return super.getResponseHeader(headerName);
+ }
+ const value = haystack.headers[headerName.toLowerCase()];
+ if ( value !== undefined && value !== '' ) { return value; }
+ return null;
+ }
+ getAllResponseHeaders() {
+ const haystack = xhrInstances.get(this);
+ if ( haystack === undefined || this.readyState < this.HEADERS_RECEIVED ) {
+ return super.getAllResponseHeaders();
+ }
+ const out = [];
+ for ( const [ name, value ] of Object.entries(haystack.headers) ) {
+ if ( !value ) { continue; }
+ out.push(`${name}: ${value}`);
+ }
+ if ( out.length !== 0 ) { out.push(''); }
+ return out.join('\r\n');
+ }
  };
 }