Update the default CSS parsing/combining/minifying tools

History.md

@@ -1,5 +1,26 @@
 ## v.NEXT
 
+* Meteor's internal `minifier-css` package has been updated to use `postcss`
+  for CSS parsing and minifying, instead of the abandoned `css-parse` and
+  `css-stringify` packages. Changes made to the `CssTools` API exposed by the
+  `minifier-css` package are mostly backwards compatible (the
+  `standard-minifier-css` package that uses it didn't have to change for
+  example), but now that we're using `postcss` the AST accepted and returned
+  from certain functions is different. This could impact developers who are
+  tying into Meteor's internal `minifier-css` package directly. The AST based 
+  function changes are:
+
+  * `CssTools.parseCss` now returns a PostCSS
+    [`Root`](http://api.postcss.org/Root.html) object.    
+  * `CssTools.stringifyCss` expects a PostCSS `Root` object as its first
+    parameter.    
+  * `CssTools.mergeCssAsts` expects an array of PostCSS `Root` objects as its
+    first parameter.    
+  * `CssTools.rewriteCssUrls` expects a PostCSS `Root` object as its first
+    parameter.
+
+  [PR #9263](https://github.com/meteor/meteor/pull/9263)
+
 * Dynamically `import()`ed modules will now be fetched from the
   application server using an HTTP POST request, rather than a WebSocket
   message. This strategy has all the benefits of the previous strategy,