Fix source map spec

Implementation switched from the header to the magic comment.

Author: elia

spec/integration/source_map_spec.rb

@@ -2,17 +2,23 @@
 require 'opal/source_map'
 
 describe Opal::SourceMap do
-  before { get '/assets/source_map_example.js' }
+  before do
+    expect(Rails.application.config.opal.source_map_enabled).to be_true
+    get '/assets/source_map_example.js'
+  end
+
+  let(:map_url) { extract_map_url(response) }
 
   let(:map_body) do
-    get response.headers['X-SourceMap']
+    get map_url
+    raise "#{response.status}\n\n#{response.body}" unless response.success?
     response.body
   end
 
   let(:map) { JSON.parse(map_body) }
 
-  it 'has the source map header' do
-    expect(response.headers['X-SourceMap']).to be_present
+  it 'has the source map header or magic comment' do
+    expect(extract_map_url(response)).to be_present
   end
 
   it "the map is a valid json" do
@@ -27,4 +33,10 @@
     expect(pathname.exist?).to be_true
   end
 
+
+  def extract_map_url response
+    response.headers['X-SourceMap'] or
+    response.body.scan(%r{^//@ sourceMappingURL=([^\n]+)}).flatten.first.strip
+  end
+
 end

test_app/config/application.rb

@@ -68,5 +68,8 @@ class Application < Rails::Application
 
     # Version of your assets, change this if you want to expire all your assets
     config.assets.version = '1.0'
+
+    # Disabled by default, we need it for tests
+    config.opal.source_map_enabled = true
   end
 end