Bad source map path in subfolder install

My subfolder install kept giving errors in Firefox console about the fact that it is unable to find source maps.

Source map error: request failed with status 404 Resource URL: […1d82fc1b0c7d1f24b7b71256a4eb4860f1aa96444925a361d8c24425c.js]( Source Map URL: /assets/

As you can see, the /community path prefix is missing from the source map URL.

So I did a little digging.

lib/tasks/assets.rake does this:

  assets = cdn_relative_path("/assets")
  source_map_root = assets + ((d = File.dirname(from)) == "." ? "" : "/#{d}")

Now cdn_relative_path in lib/global_path.rb looks like this.

module GlobalPath
  def path(p)

  def cdn_path(p)
    GlobalSetting.cdn_url.blank? ? p : "#{GlobalSetting.cdn_url}#{path(p)}"

  def upload_cdn_path(p)
    if SiteSetting.Upload.s3_cdn_url.present?
      p =

    (p =~ /^http/ || p =~ /^\/\//) ? p : cdn_path(p)

  def cdn_relative_path(path)
    if (cdn_url = GlobalSetting.cdn_url).present?
      URI.parse(cdn_url).path + path

As you can see, both cdn_path and upload_cdn_path eventually call the path method which makes sure that the subfolder is being prefixed. However, cdn_relative_path does not call the path method, it just returns its parameter (called… path).

BTW I think cdn_path needs to return path(p) in the middle part of the ternary as well?

@sam is the expert on source maps

@david has fussed with this in the past, but yeah getting the paths right for CDN + subfolder is not easy. I am open to a PR that fixes it provided this is very targeted at your magic combo and does not regress any places that work now.