Drop the bundled shim

It's no longer needed with full support for import maps in all modern browsers.

Author: dhh

README.md

@@ -4,7 +4,7 @@
 
 With this approach you'll ship many small JavaScript files instead of one big JavaScript file. Thanks to HTTP/2 that no longer carries a material performance penalty during the initial transport, and in fact offers substantial benefits over the long run due to better caching dynamics. Whereas before any change to any JavaScript file included in your big bundle would invalidate the cache for the whole bundle, now only the cache for that single file is invalidated.
 
-There's [native support for import maps in Chrome/Edge 89+/Firefox 108+](https://caniuse.com/?search=importmap), and [a shim available](https://github.com/guybedford/es-module-shims) for any browser with basic ESM support. So your app will be able to work with all the evergreen browsers.
+[Import maps are supported natively in all major, modern browsers](https://caniuse.com/?search=importmap). If you need to work with legacy browsers without native support, you can explore using [the shim available](https://github.com/guybedford/es-module-shims).
 
 
 ## Installation

app/assets/javascripts/es-module-shims.js

@@ -1,13 +1,11 @@
 module Importmap::ImportmapTagsHelper
   # Setup all script tags needed to use an importmap-powered entrypoint (which defaults to application.js)
-  def javascript_importmap_tags(entry_point = "application", shim: true, importmap: Rails.application.importmap)
+  def javascript_importmap_tags(entry_point = "application", importmap: Rails.application.importmap)
     safe_join [
       javascript_inline_importmap_tag(importmap.to_json(resolver: self)),
       javascript_importmap_module_preload_tags(importmap),
-      (javascript_importmap_shim_nonce_configuration_tag if shim),
-      (javascript_importmap_shim_tag if shim),
       javascript_import_module_tag(entry_point)
-    ].compact, "\n"
+    ], "\n"
   end
 
   # Generate an inline importmap tag using the passed `importmap_json` JSON string.
@@ -17,20 +15,6 @@ def javascript_inline_importmap_tag(importmap_json = Rails.application.importmap
       type: "importmap", "data-turbo-track": "reload", nonce: request&.content_security_policy_nonce
   end
 
-  # Configure es-modules-shim with nonce support if the application is using a content security policy.
-  def javascript_importmap_shim_nonce_configuration_tag
-    if request&.content_security_policy
-      tag.script({ nonce: request.content_security_policy_nonce }.to_json.html_safe,
-        type: "esms-options", nonce: request.content_security_policy_nonce)
-    end
-  end
-
-  # Include the es-modules-shim needed to make importmaps work in browsers without native support (like Firefox + Safari).
-  def javascript_importmap_shim_tag(minimized: true)
-    javascript_include_tag minimized ? "es-module-shims.min.js" : "es-module-shims.js",
-      async: true, "data-turbo-track": "reload", nonce: request&.content_security_policy_nonce
-  end
-
   # Import a named JavaScript module(s) using a script-module tag.
   def javascript_import_module_tag(*module_names)
     imports = Array(module_names).collect { |m| %(import "#{m}") }.join("\n")

app/assets/javascripts/es-module-shims.js.map

@@ -43,7 +43,6 @@ class Engine < ::Rails::Engine
 
     initializer "importmap.assets" do |app|
       if app.config.respond_to?(:assets)
-        app.config.assets.precompile += %w( es-module-shims.js es-module-shims.min.js es-module-shims.js.map )
         app.config.assets.paths << Rails.root.join("app/javascript")
         app.config.assets.paths << Rails.root.join("vendor/javascript")
       end

app/assets/javascripts/es-module-shims.min.js

@@ -19,11 +19,6 @@ def content_security_policy_nonce
     end
   end
 
-  test "javascript_importmap_tags with and without shim" do
-    assert_match /shim/, javascript_importmap_tags("application")
-    assert_no_match /shim/, javascript_importmap_tags("application", shim: false)
-  end
-
   test "javascript_inline_importmap_tag" do
     assert_match \
       %r{<script type="importmap" data-turbo-track="reload">{\n  \"imports\": {\n    \"md5\": \"https://cdn.skypack.dev/md5\",\n    \"not_there\": \"/nowhere.js\"\n  }\n}</script>},
@@ -48,8 +43,6 @@ def content_security_policy_nonce
     @request = FakeRequest.new("iyhD0Yc0W+c=")
 
     assert_match /nonce="iyhD0Yc0W\+c="/, javascript_inline_importmap_tag
-    assert_match /nonce="iyhD0Yc0W\+c="/, javascript_importmap_shim_nonce_configuration_tag
-    assert_match /nonce="iyhD0Yc0W\+c="/, javascript_importmap_shim_tag
     assert_match /nonce="iyhD0Yc0W\+c="/, javascript_import_module_tag("application")
     assert_match /nonce="iyhD0Yc0W\+c="/, javascript_importmap_module_preload_tags
   ensure