[bug] link set setAttribute disabled not work about css-vars-ponyfill

[jhildenbiddle]

The HTML <style> element does not support the disabled attribute. IE supports it, but no other browser does. This is why the ponyfill ignores the disabled attribute on <style> elements.

https://stackoverflow.com/questions/5757231/disabled-true-can-be-set-dynamically-on-style-why-not-statically

The ponyfill does support the disabled property on the HTMLLinkElement.sheet and HTMLStyleElement.sheet objects. Alternatively, you can also just remove the <link> or <style> element from the DOM.

Parsed cssTree and pasreVars should be cached and not re-parsed

See the __cssVars property attached to any <link> or <style> element with a data-cssvars="src" attribute. You'll find the the cssTree object and the original CSS text stored there. The CSS text is used for comparison because any change to it will require generating new CSS output (i.e., the ponyfill has to be aware of more than just variable changes). Variables are cached elsewhere and do not need to be stored on a per-node basis:

css-vars-ponyfill/src/index.js

Lines 65 to 72 in 9811bbd

	const variableStore = {
	// Parsed DOM values (from <link> and <style> nodes)
	dom : {},
	// Temporary storage for each job
	job : {},
	// Persisted options.variables values
	user: {}
	};

You are right about the unnecessary processing here though:

css-vars-ponyfill/src/index.js

Lines 416 to 424 in 9811bbd

	const nodeCSS = cssArray[i];
	// Node data cache
	node.__cssVars = node.__cssVars || {};
	node.__cssVars.text = nodeCSS;
	// Only process CSS contains a custom property
	// declarations or function
	if (regex.cssVars.test(nodeCSS)) {

Instead of blindly assigning nodeCSS to node.__cssVars.text, the ponyfill should be checking to see if node.__cssVars.text exists and if it matches nodeCSS to determine if the node needs to be processed.

const nodeCSS = cssArray[i];
const hasCSSCache = Boolean(node.__cssVars && node.__cssVars.text);
const hasCSSChanged = hasCSSCache && node.__cssVars.text !== nodeCSS;

// Node data cache
node.__cssVars = node.__cssVars || {};
node.__cssVars.text = nodeCSS;

// Only process CSS if it has changed or contains a
// custom property declarations or function
if ((hasCSSCache && hasCSSChanged) || regex.cssVars.test(nodeCSS)) {

I'll have to do some testing to verify that the change is is beneficial. It's been a while since I've looked at the code.