javascript_pack_tag handles repetition of individual chunks. Closes #39

lib/webpacker/helper.rb

@@ -87,23 +87,58 @@ def favicon_pack_tag(name, **options)
   #   <script src="/packs/map~runtime-16838bab065ae1e314.chunk.js" data-turbolinks-track="reload" defer="true"></script>
   #   <script src="/packs/map-16838bab065ae1e314.chunk.js" data-turbolinks-track="reload" defer="true"></script>
   #
-  # DO:
-  #
-  #   <%= javascript_pack_tag 'calendar', 'map' %>
-  #
-  # DON'T:
-  #
-  #   <%= javascript_pack_tag 'calendar' %>
-  #   <%= javascript_pack_tag 'map' %>
+  # There should be at least one javascript_pack_tag in the main template
+  # ActionView will call first partial templates and after the main one
+  # We don't emit chunks in partials, just in the main template
+  # In partial we just queue what has to be emitted in the main
+
   def javascript_pack_tag(*names, defer: true, **options)
-    if @javascript_pack_tag_loaded
-      raise "To prevent duplicated chunks on the page, you should call javascript_pack_tag only once on the page. " \
-      "Please refer to https://github.com/shakacode/shakapacker/blob/master/README.md#usage for the usage guide"
+
+    options[:defer] = defer
+    if !defined?(@emitted)
+      @emitted = {}
     end
+    if !defined?(@queue)
+      @queue = []
+    end
+
+    @includetags = "".html_safe
+    @newline = "".html_safe
+
+    def emit_without_repetition(source, defer, options)
+        if @emitted.key?(source) && @emitted[source][:defer] != defer
+          raise "Chunk #{source} already emitted with defer value "\
+            "#{@emitted[source][:defer]}. Trying to emit with different "\
+            "defer value is a conflict."
+        elsif [email protected]?(source)
+          @includetags += @newline + javascript_include_tag(source, options)
+          @newline = "\n".html_safe
+          @emitted[source] = { defer: defer }
+        end
+    end
+
+    # Determine if we are in a partial template or in the main one
+    partial = caller.filter{|c| c.include?('partial_renderer')}.count > 0
+
+
+    #puts names, partial;
+    #debugger
+    sources = sources_from_manifest_entrypoints(names, type: :javascript)
 
-    @javascript_pack_tag_loaded = true
+    if partial
+      sources.each do |source|
+        @queue |= [source]
+      end
+    else # main template (layout?)
+      sources.each do |source|
+        emit_without_repetition(source, defer, options)
+      end
+      @queue.each do |source|
+        emit_without_repetition(source, defer, options)
+      end
+    end 
 
-    javascript_include_tag(*sources_from_manifest_entrypoints(names, type: :javascript), **options.tap { |o| o[:defer] = defer })
+    return @includetags
   end
 
   # Creates a link tag, for preloading, that references a given Webpacker asset.

test/helper_test.rb

@@ -106,12 +106,13 @@ def test_javascript_pack_tag
       javascript_pack_tag("application", "bootstrap")
   end
 
-  def test_javascript_pack_with_no_defer_tag
-    assert_equal \
-      %(<script src="/packs/vendors~application~bootstrap-c20632e7baf2c81200d3.chunk.js"></script>\n) +
+  SCRIPTS_APPLICATION_BOOTSTRAP = %(<script src="/packs/vendors~application~bootstrap-c20632e7baf2c81200d3.chunk.js"></script>\n) +
         %(<script src="/packs/vendors~application-e55f2aae30c07fb6d82a.chunk.js"></script>\n) +
         %(<script src="/packs/application-k344a6d59eef8632c9d1.js"></script>\n) +
-        %(<script src="/packs/bootstrap-300631c4f0e0f9c865bc.js"></script>),
+        %(<script src="/packs/bootstrap-300631c4f0e0f9c865bc.js"></script>)
+
+  def test_javascript_pack_with_no_defer_tag
+    assert_equal SCRIPTS_APPLICATION_BOOTSTRAP,
       javascript_pack_tag("application", "bootstrap", defer: false)
   end
 
@@ -132,15 +133,10 @@ def test_javascript_pack_tag_symbol
   end
 
   def test_javascript_pack_tag_multiple_invocations
-    error = assert_raises do
-      javascript_pack_tag(:application)
-      javascript_pack_tag(:bootstrap)
-    end
+    r = javascript_pack_tag(:application, defer: false)
+    r += "\n".html_safe + javascript_pack_tag(:bootstrap, defer: false)
 
-    assert_equal \
-      "To prevent duplicated chunks on the page, you should call javascript_pack_tag only once on the page. " +
-        "Please refer to https://github.com/shakacode/shakapacker/blob/master/README.md#usage for the usage guide",
-      error.message
+    assert_equal SCRIPTS_APPLICATION_BOOTSTRAP, r
   end
 
   def application_stylesheet_chunks