Add docs for hooks issue with multiple packs

[samtgarson]

Context in this comment: rails/webpacker#2932 (comment)

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This change is 

[justin808]

javascript_pack_tag

@samtgarson This is really useful, but this is the wrong place.

@Judahmeek any suggestion for the right place? We have a big doc PR update: #1367

and we document the v6 setup in https://github.com/shakacode/react_on_rails_tutorial_with_ssr_and_hmr_fast_refresh

And the real solution is for rails/webpacker to throw an error if the javascript_pack_tag is called multiple times.

[samtgarson]

Great! Yeah, the only reason I put it here was that this page comes up in google searches a lot related to react/rails/errors with hooks (which was how I discovered the issue with multiple bundles).

(surely the real real fix is for Webpacker to allow multiple pack tags but just not include duplicate shared packs...?)

[justin808]

@Judahmeek how about a troubleshooting document?

[Judahmeek]

@justin808 how would such a document differ from this here?

Things to add:

# in helper file
module ReactHelper
  def append_javascript_pack(pack_name)
    content_for :view_pack_tags do
      " #{pack_name}"
    end
  end
end

# in partials
<% append_javascript_pack("packs separated by-spaces") %>

# in layout
    <% 
      # Because content_for appends as strings separated by white spaces, pack names are supposed to be space separated too.
      # This way the separation is consistent regardless of their sources.
      pack_tag_args = (yield :view_pack_tags).strip.split(" ")

      pack_tag_args << "oneflare-header" unless skip_header?
      pack_tag_args << "oneflare-footer" unless skip_footer?
      pack_tag_args << "oneflare-user-switcher" if Rails.env.development? || Rails.env.staging?
    %>
    <%= javascript_pack_tag *pack_tag_args unless pack_tag_args.empty? %>

[justin808]

@Judahmeek the addition above is good.

Might be pretty self-explanatory if this gets merged: https://github.com/rails/webpacker/pull/3083/files

[justin808]

@Judahmeek can you close this and a docs page to https://github.com/shakacode/shakapacker/.

[Judahmeek]

@justin808 This definitely seems like the right place to me.

This doc is directly related to #1198 as is @samtgarson's edit.

[Judahmeek]

Does rails/webpacker#2708 address this issue?

[justin808]

@Judahmeek, absolutely not. This is a big GOTCHA with the newer rails/webpacker.

[justin808]

This is resolved in newer versions of ShakaPacker with

https://github.com/shakacode/shakapacker#view-helper-append_javascript_pack_tag