feat(css): account for escaped ':' in css selectors (#3087)

Prior to this commit, when using `scoped: true` on a component, CSS
class names with special characters are mangled due to incorrect escaping. 
This is particularly obvious when using a framework like Tailwind, which
makes extensive use of special characters (:) in class names.

With this commit `\:` remains escaped in CSS selectors when introducing
scope class

src/utils/shadow-css.ts

@@ -91,6 +91,7 @@ const extractCommentsWithHash = (input: string): string[] => {
 
 const _ruleRe = /(\s*)([^;\{\}]+?)(\s*)((?:{%BLOCK%}?\s*;?)|(?:\s*;))/g;
 const _curlyRe = /([{}])/g;
+const _selectorPartsRe = /(^.*?[^\\])??((:+)(.*)|$)/;
 const OPEN_CURLY = '{';
 const CLOSE_CURLY = '}';
 const BLOCK_PLACEHOLDER = '%BLOCK%';
@@ -256,17 +257,19 @@ const selectorNeedsScoping = (selector: string, scopeSelector: string) => {
   return !re.test(selector);
 };
 
+const injectScopingSelector = (selector: string, scopingSelector: string) => {
+  return selector.replace(_selectorPartsRe, (_: string, before = '', _colonGroup: string, colon = '', after = '') => {
+    return before + scopingSelector + colon + after;
+  });
+};
+
 const applySimpleSelectorScope = (selector: string, scopeSelector: string, hostSelector: string) => {
   // In Android browser, the lastIndex is not reset when the regex is used in String.replace()
   _polyfillHostRe.lastIndex = 0;
   if (_polyfillHostRe.test(selector)) {
     const replaceBy = `.${hostSelector}`;
     return selector
-      .replace(_polyfillHostNoCombinatorRe, (_, selector) => {
-        return selector.replace(/([^:]*)(:*)(.*)/, (_: string, before: string, colon: string, after: string) => {
-          return before + replaceBy + colon + after;
-        });
-      })
+      .replace(_polyfillHostNoCombinatorRe, (_, selector) => injectScopingSelector(selector, replaceBy))
       .replace(_polyfillHostRe, replaceBy + ' ');
   }
 
@@ -292,10 +295,7 @@ const applyStrictSelectorScope = (selector: string, scopeSelector: string, hostS
       // remove :host since it should be unnecessary
       const t = p.replace(_polyfillHostRe, '');
       if (t.length > 0) {
-        const matches = t.match(/([^:]*)(:*)(.*)/);
-        if (matches) {
-          scopedP = matches[1] + className + matches[2] + matches[3];
-        }
+        scopedP = injectScopingSelector(t, className);
       }
     }
 

src/utils/test/scope-css.spec.ts

@@ -143,6 +143,15 @@ describe('ShadowCss', function () {
     expect(s('[is="one"] {}', 'a')).toEqual('[is="one"].a {}');
   });
 
+  it('should handle escaped ":" in selector', () => {
+    expect(s('\\:one {}', 'a')).toEqual('\\:one.a {}');
+    expect(s('one\\:two {}', 'a')).toEqual('one\\:two.a {}');
+    expect(s('one\\:two:hover {}', 'a')).toEqual('one\\:two.a:hover {}');
+    expect(s('one\\:two::before {}', 'a')).toEqual('one\\:two.a::before {}');
+    expect(s('one\\:two::before:hover {}', 'a')).toEqual('one\\:two.a::before:hover {}');
+    expect(s('one\\:two:not(.three\\:four) {}', 'a')).toEqual('one\\:two.a:not(.three\\:four) {}');
+  });
+
   describe(':host', () => {
     it('should handle no context, commentOriginalSelector', () => {
       expect(s(':host {}', 'a', true)).toEqual('/*!@:host*/.a-h {}');