Clear return value of vapi.js content script

[Rob--W]

Upon start-up, uBlock runs all content scripts in manifest.json using chrome.tabs.executeScript. When this API is used, the value of the last expression is automatically cloned and transferred to the callback of chrome.tabs.executeScript. This is convenient if needed, and a performance burden otherwise (the latter is the case for uBlock).

There are three content scripts that need to be checked:

• vapi.js
  The last expression is often the vAPI object, and it is relatively expensive to clone this object. This commit sets the value of the last expression to void 0 to solve this inefficiency.
  

  uBlock/platform/chromium/vapi.js

  Lines 51 to 56 in 820ec69

  	vAPI = window.vAPI = vAPI instanceof Object && vAPI.uBO === true
  	? vAPI
  	: { uBO: true };
  	}
  	/******************************************************************************/

• vapi-client.js
  No action needed yet; The last expression is vAPI.shutdown.add(...), which has a void return value.
  

  uBlock/platform/chromium/vapi-client.js

  Lines 49 to 53 in 820ec69

  	vAPI.shutdown = {
  	jobs: [],
  	add: function(job) {
  	this.jobs.push(job);
  	},

  
  

  uBlock/platform/chromium/vapi-client.js

  Lines 436 to 447 in 820ec69

  	vAPI.shutdown.add(function() {
  	vAPI.messaging.shutdown();
  	window.vAPI = undefined;
  	});
  	// https://www.youtube.com/watch?v=rT5zCHn0tsg
  	// https://www.youtube.com/watch?v=E-jS4e3zacI
  	/******************************************************************************/
  	/******************************************************************************/
  	} // <<<<<<<< end of HUGE-IF-BLOCK

• contentscript.js
  No action needed yet; The last expression is an immediately-invoked function expression without return value.
  

  uBlock/src/js/contentscript.js

  Lines 1267 to 1417 in 820ec69

  	(function bootstrap() {
  	var bootstrapPhase2 = function(ev) {
  	// This can happen on Firefox. For instance:
  	// https://github.com/gorhill/uBlock/issues/1893
  	if ( window.location === null ) { return; }
  	if ( ev ) {
  	document.removeEventListener('DOMContentLoaded', bootstrapPhase2);
  	}
  	if ( vAPI instanceof Object === false ) {
  	return;
  	}
  	if ( vAPI.domWatcher instanceof Object ) {
  	vAPI.domWatcher.start();
  	}
  	// Element picker works only in top window for now.
  	if (
  	window !== window.top ||
  	vAPI.domFilterer instanceof Object === false
  	) {
  	return;
  	}
  	// To send mouse coordinates to main process, as the chrome API fails
  	// to provide the mouse position to context menu listeners.
  	// https://github.com/chrisaljoudi/uBlock/issues/1143
  	// Also, find a link under the mouse, to try to avoid confusing new tabs
  	// as nuisance popups.
  	// Ref.: https://developer.mozilla.org/en-US/docs/Web/Events/contextmenu
  	var onMouseClick = function(ev) {
  	var elem = ev.target;
  	while ( elem !== null && elem.localName !== 'a' ) {
  	elem = elem.parentElement;
  	}
  	vAPI.messaging.send(
  	'contentscript',
  	{
  	what: 'mouseClick',
  	x: ev.clientX,
  	y: ev.clientY,
  	url: elem !== null && ev.isTrusted !== false ? elem.href : ''
  	}
  	);
  	};
  	document.addEventListener('mousedown', onMouseClick, true);
  	// https://github.com/gorhill/uMatrix/issues/144
  	vAPI.shutdown.add(function() {
  	document.removeEventListener('mousedown', onMouseClick, true);
  	});
  	};
  	var bootstrapPhase1 = function(response) {
  	// cosmetic filtering engine aka 'cfe'
  	var cfeDetails = response && response.specificCosmeticFilters;
  	if ( !cfeDetails || !cfeDetails.ready ) {
  	vAPI.domWatcher = vAPI.domCollapser = vAPI.domFilterer =
  	vAPI.domSurveyor = vAPI.domIsLoaded = null;
  	return;
  	}
  	if ( response.noCosmeticFiltering ) {
  	vAPI.domFilterer = null;
  	vAPI.domSurveyor = null;
  	} else {
  	var domFilterer = vAPI.domFilterer;
  	if ( response.noGenericCosmeticFiltering || cfeDetails.noDOMSurveying ) {
  	vAPI.domSurveyor = null;
  	}
  	domFilterer.exceptions = cfeDetails.exceptionFilters;
  	domFilterer.hideNodeAttr = cfeDetails.hideNodeAttr;
  	domFilterer.hideNodeStyleSheetInjected =
  	cfeDetails.hideNodeStyleSheetInjected === true;
  	domFilterer.addCSSRule(
  	cfeDetails.declarativeFilters,
  	'display:none!important;'
  	);
  	domFilterer.addCSSRule(
  	cfeDetails.highGenericHideSimple,
  	'display:none!important;',
  	{ type: 'simple', lazy: true }
  	);
  	domFilterer.addCSSRule(
  	cfeDetails.highGenericHideComplex,
  	'display:none!important;',
  	{ type: 'complex', lazy: true }
  	);
  	domFilterer.addCSSRule(
  	cfeDetails.injectedHideFilters,
  	'display:none!important;',
  	{ injected: true }
  	);
  	domFilterer.addProceduralSelectors(cfeDetails.proceduralFilters);
  	}
  	if ( cfeDetails.networkFilters.length !== 0 ) {
  	vAPI.userStylesheet.add(
  	cfeDetails.networkFilters + '\n{display:none!important;}');
  	}
  	vAPI.userStylesheet.apply();
  	// Library of resources is located at:
  	// https://github.com/gorhill/uBlock/blob/master/assets/ublock/resources.txt
  	if ( response.scriptlets ) {
  	vAPI.injectScriptlet(document, response.scriptlets);
  	vAPI.injectedScripts = response.scriptlets;
  	}
  	if ( vAPI.domSurveyor instanceof Object ) {
  	vAPI.domSurveyor.start(cfeDetails);
  	}
  	// https://github.com/chrisaljoudi/uBlock/issues/587
  	// If no filters were found, maybe the script was injected before
  	// uBlock's process was fully initialized. When this happens, pages
  	// won't be cleaned right after browser launch.
  	if (
  	typeof document.readyState === 'string' &&
  	document.readyState !== 'loading'
  	) {
  	bootstrapPhase2();
  	} else {
  	document.addEventListener('DOMContentLoaded', bootstrapPhase2);
  	}
  	};
  	// This starts bootstrap process.
  	vAPI.messaging.send(
  	'contentscript',
  	{
  	what: 'retrieveContentScriptParameters',
  	url: window.location.href,
  	isRootFrame: window === window.top,
  	charset: document.characterSet
  	},
  	bootstrapPhase1
  	);
  	})();
  	/******************************************************************************/
  	/******************************************************************************/
  	/******************************************************************************/
  	} // <<<<<<<< end of HUGE-IF-BLOCK

[gorhill]

Thanks.