Backport 'Fix webpacker crashes on missing icons' to v0.26 (#11045)

Co-authored-by: Antti Hukkanen <antti.hukkanen@mainiotech.fi>

decidim-core/app/helpers/decidim/layout_helper.rb

@@ -74,18 +74,26 @@ def external_icon(path, options = {})
       classes = _icon_classes(options) + ["external-icon"]
 
       if path.split(".").last == "svg"
+        icon_path = application_path(path)
+        return unless icon_path
+
         attributes = { class: classes.join(" ") }.merge(options)
-        asset = File.read(application_path(path))
+        asset = File.read(icon_path)
         asset.gsub("<svg ", "<svg#{tag_builder.tag_options(attributes)} ").html_safe
       else
         image_pack_tag(path, class: classes.join(" "), style: "display: none")
       end
     end
 
     def application_path(path)
-      img_path = asset_pack_path(path)
-      img_path = URI(img_path).path if Decidim.cors_enabled
-      Rails.root.join("public/#{img_path}")
+      # Force the path to be returned without the protocol and host even when a
+      # custom asset host has been defined. The host parameter needs to be a
+      # non-nil because otherwise it will be set to the asset host at
+      # ActionView::Helpers::AssetUrlHelper#compute_asset_host.
+      img_path = asset_pack_path(path, host: "", protocol: :relative)
+      Rails.public_path.join(img_path.sub(%r{^/}, ""))
+    rescue ::Webpacker::Manifest::MissingEntryError
+      nil
     end
 
     # Allows to create role attribute according to accessibility rules

decidim-core/spec/helpers/decidim/layout_helper_spec.rb

@@ -0,0 +1,87 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+module Decidim
+  describe LayoutHelper do
+    describe "#external_icon" do
+      subject { helper.external_icon(path) }
+
+      context "when the icon exists" do
+        let(:path) { "media/images/google.svg" }
+
+        it "returns the SVG element" do
+          expect(subject).to match(/^<svg.*/)
+        end
+      end
+
+      context "when the icon does not exist" do
+        let(:path) { "media/images/hooli.svg" }
+
+        it "returns nil" do
+          expect(subject).to be_nil
+        end
+      end
+
+      context "when using a custom host" do
+        let(:path) { "media/images/google.svg" }
+
+        before do
+          allow(helper.config).to receive(:asset_host).and_return("https://assets.example.org")
+        end
+
+        # Ensures the asset_path_pack would normally return the asset host in
+        # case there are any API changes in Rails.
+        it "works expectedly" do
+          expect(helper.asset_pack_path(path)).to match(%r{^https://assets\.example.org/packs-test})
+        end
+
+        it "returns the SVG element" do
+          expect(subject).to match(/^<svg.*/)
+        end
+      end
+    end
+
+    describe "#application_path" do
+      subject { helper.application_path(path) }
+
+      context "when the icon exists" do
+        let(:path) { "media/images/google.svg" }
+
+        it "returns the file path to the asset" do
+          expect(subject.to_s).to match(
+            %r{^#{Rails.public_path}/packs-test/media/images/google-[a-z0-9]+\.svg}
+          )
+        end
+      end
+
+      context "when the icon does not exist" do
+        let(:path) { "media/images/hooli.svg" }
+
+        it "returns nil" do
+          expect(subject).to be_nil
+        end
+      end
+
+      context "when using a custom host" do
+        let(:path) { "media/images/google.svg" }
+
+        before do
+          allow(helper.config).to receive(:asset_host).and_return("https://assets.example.org")
+        end
+
+        # Ensures the asset_path_pack would normally return the asset host in
+        # case there are any API changes in Rails.
+        it "works expectedly" do
+          expect(helper.asset_pack_path(path)).to match(%r{^https://assets\.example.org/packs-test})
+        end
+
+        it "returns the file path to the asset" do
+          expect(subject.to_s).to match(
+            %r{^#{Rails.public_path}/packs-test/media/images/google-[a-z0-9]+\.svg}
+          )
+        end
+      end
+    end
+  end
+end