Multiple ignored CSS blocks

If there are multiple ignored CSS blocks within a single clean-css
warning message, only the first is replaced with the ignore code.
This means that some ingored blocks are simply deleted from the output.

The problem is simply that the RegExp is only applied once, despite
having the global flag set on it.  This is fixed by calling `exec` on
the RegExp until it yields no further matches.

Added a test for this error case.

Fixes terser#180

Author: chrisstaite-menlo

src/htmlminifier.js

@@ -905,8 +905,8 @@ async function minifyHTML(value, options, partialMarkup) {
 
               const ids = [];
               new CleanCSS().minify(wrapCSS(text, type)).warnings.forEach(function (warning) {
-                const match = uidPattern.exec(warning);
-                if (match) {
+                let match;
+                while ((match = uidPattern.exec(warning))) {
                   const id = uidAttr + match[2] + uidAttr;
                   text = text.replace(id, ignoreCSS(id));
                   ids.push(id);

tests/minifier.spec.js

@@ -3594,3 +3594,14 @@ test('minify Content-Security-Policy', async () => {
   input = '<meta http-equiv="content-security-policy" content="default-src \'self\'; img-src https://*;">';
   expect(await minify(input)).toBe(input);
 });
+
+test('minify CSS multiple ignore in single warning', async () => {
+  const input = '<style type="text/css">\n{% ignore1 %}\na {\n{% ignore2 %}\n}\n{% ignore3 %}\n</style>';
+  const output = '<style type="text/css">\n{% ignore1 %}\na{\n{% ignore2 %}\n}\n{% ignore3 %}\n</style>';
+  expect(await minify(input, {
+    ignoreCustomFragments: [/\{%[\s\S]*?%\}/],
+    minifyCSS: {
+      level: 0
+    }
+  })).toBe(output);
+});