Fix synchronously loading/applying stylesheets on page load.

[chipx86]

Starting in 2.0, stylesheet loading became asynchronous, through the
usage of promises for both calculating the list of stylesheets and the
initial call to less.refresh(). This resulted in visual issues while
loading on some browsers (noticed in Firefox and Safari), along with
breakages of any custom JavaScript that depended on the computed style
of elements on the page, due to race conditions.

This change preserves the promise for initial page loading, in order to
retain support for less.pageLoadFinished, but immediately executes the
stylesheet scan (through a new less.registerStylesheetsImmediately
function) and the less.refresh() call. That resulting behavior matches
versions of less prior to 2.0.

This unveiled a regression in registering functions, both in the browser
and in unit tests, that was not previously noticed due to the
asynchronous load. Registered functions would have a less variable set
to the less options, and not less itself, when not going through the
asynchronous loading mode. This meant that both unit tests and
real-world function registration would break when the sync page loading
was fixed. Overriding window.less to point to the actual less module and
not less.options during bootstrap fixes this.

This fixes #2317.

[lukeapage]

you don't call less.registerStylesheetsImmediately from anywhere? and you have removed the call to less.registerStylesheets and that isn't called anywhere..

I guess you just need to call less.registerStylesheetsImmediately from bootstrap ?

otherwise, many thanks for tracking it down and fixing.

[chipx86]

This is the GitHub bug I mentioned in issue #2317. The line is actually there, right above the less.refresh call and promise assignment in bootstrap.js. However, GitHub appears to have a bug in the diff viewer where a delete line at the end of a file + adding a missing trailing newline to the file + adding a line results in that line getting skipped. I've already let GitHub know about it.

This is what the diff looks like for the change:

--- a/lib/less-browser/bootstrap.js
+++ b/lib/less-browser/bootstrap.js
@@ -13,14 +13,13 @@ require("./add-default-options")(window, options);

 var less = module.exports = require("./index")(window, options);

+window.less = less;
+
 if (options.onReady) {
     if (/!watch/.test(window.location.hash)) {
         less.watch();
     }

-    less.pageLoadFinished = less.registerStylesheets().then(
-        function () {
-            return less.refresh(less.env === 'development');
-        }
-    );
-}
\ No newline at end of file
+    less.registerStylesheetsImmediately();
+    less.pageLoadFinished = less.refresh(less.env === 'development');
+}

If you clone my tree and git show the commit, you'll see the line is there.

Also, would you mind trying to restart the Travis-CI build? They had some problems last night with random stalls, which was randomly affecting different builds at different points during the build process, triggering failures of 3 different types that I had noticed. Hoping that was some temporary issue on their end related to their failed upgrade and rollbacks.

[lukeapage]

Sure, restarted...

[lukeapage]

Thanks for this.

[lukeapage]

I'll release soon