DEV: Add a helper method to clear every possible theme cache (#17585)

Our theme system is very complex and it can take a while to figure out how to invalidate the various types of caches that are used throughout the theme system. So, having a single helper method that invalidates everything can be useful in emergency situations where there is no time to read through the code and figure out how to clear the various caches.

Internal ticket: t64732.

app/models/theme.rb

@@ -151,9 +151,6 @@ class Theme < ActiveRecord::Base
     end
 
     Theme.expire_site_cache!
-    ColorScheme.hex_cache.clear
-    CSP::Extension.clear_theme_extensions_cache!
-    SvgSprite.expire_cache
   end
 
   def self.compiler_version
@@ -217,6 +214,8 @@ class Theme < ActiveRecord::Base
     clear_cache!
     ApplicationSerializer.expire_cache_fragment!("user_themes")
     ColorScheme.hex_cache.clear
+    CSP::Extension.clear_theme_extensions_cache!
+    SvgSprite.expire_cache
   end
 
   def self.clear_default!

lib/discourse.rb

@@ -1028,4 +1028,14 @@ module Discourse
   def self.allow_dev_populate?
     Rails.env.development? || ENV["ALLOW_DEV_POPULATE"] == "1"
   end
+
+  # warning: this method is very expensive and shouldn't be called in places
+  # where performance matters. it's meant to be called manually (e.g. in the
+  # rails console) when dealing with an emergency that requires invalidating
+  # theme cache
+  def self.clear_all_theme_cache!
+    ThemeField.force_recompilation!
+    Theme.all.each(&:update_javascript_cache!)
+    Theme.expire_site_cache!
+  end
 end

spec/lib/discourse_spec.rb

@@ -472,4 +472,128 @@ describe Discourse do
     end
   end
 
+  context ".clear_all_theme_cache!" do
+    before do
+      setup_s3
+      SiteSetting.s3_cdn_url = "https://s3.cdn.com/gg"
+      stub_s3_store
+    end
+
+    let!(:theme) { Fabricate(:theme) }
+    let!(:upload) { Fabricate(:s3_image_upload) }
+    let!(:upload_theme_field) do
+      Fabricate(
+        :theme_field,
+        theme: theme,
+        upload: upload,
+        type_id: ThemeField.types[:theme_upload_var],
+        target_id: Theme.targets[:common],
+        name: "imajee",
+        value: "",
+      )
+    end
+    let!(:basic_html_field) do
+      Fabricate(
+        :theme_field,
+        theme: theme,
+        type_id: ThemeField.types[:html],
+        target_id: Theme.targets[:common],
+        name: "head_tag",
+        value: <<~HTML
+          <script type="text/discourse-plugin" version="0.1">
+            console.log(settings.uploads.imajee);
+          </script>
+        HTML
+      )
+    end
+    let!(:js_field) do
+      Fabricate(
+        :theme_field,
+        theme: theme,
+        type_id: ThemeField.types[:js],
+        target_id: Theme.targets[:extra_js],
+        name: "somefile.js",
+        value: <<~JS
+          console.log(settings.uploads.imajee);
+        JS
+      )
+    end
+    let!(:scss_field) do
+      Fabricate(
+        :theme_field,
+        theme: theme,
+        type_id: ThemeField.types[:scss],
+        target_id: Theme.targets[:common],
+        name: "scss",
+        value: <<~SCSS
+          .something { background: url($imajee); }
+        SCSS
+      )
+    end
+
+    it "invalidates all JS and CSS caches" do
+      Stylesheet::Manager.clear_theme_cache!
+
+      old_upload_url = Discourse.store.cdn_url(upload.url)
+
+      head_tag_script = Nokogiri::HTML5.fragment(
+        Theme.lookup_field(theme.id, :desktop, "head_tag")
+      ).css('script').first
+      head_tag_js = JavascriptCache.find_by(digest: head_tag_script[:src][/\h{40}/]).content
+      expect(head_tag_js).to include(old_upload_url)
+
+      js_file_script = Nokogiri::HTML5.fragment(
+        Theme.lookup_field(theme.id, :extra_js, nil)
+      ).css('script').first
+      file_js = JavascriptCache.find_by(digest: js_file_script[:src][/\h{40}/]).content
+      expect(file_js).to include(old_upload_url)
+
+      css_link_tag = Nokogiri::HTML5.fragment(
+        Stylesheet::Manager.new(theme_id: theme.id).stylesheet_link_tag(:desktop_theme, 'all')
+      ).css('link').first
+      css = StylesheetCache.find_by(digest: css_link_tag[:href][/\h{40}/]).content
+      expect(css).to include("url(#{old_upload_url})")
+
+      SiteSetting.s3_cdn_url = "https://new.s3.cdn.com/gg"
+      new_upload_url = Discourse.store.cdn_url(upload.url)
+
+      head_tag_script = Nokogiri::HTML5.fragment(
+        Theme.lookup_field(theme.id, :desktop, "head_tag")
+      ).css('script').first
+      head_tag_js = JavascriptCache.find_by(digest: head_tag_script[:src][/\h{40}/]).content
+      expect(head_tag_js).to include(old_upload_url)
+
+      js_file_script = Nokogiri::HTML5.fragment(
+        Theme.lookup_field(theme.id, :extra_js, nil)
+      ).css('script').first
+      file_js = JavascriptCache.find_by(digest: js_file_script[:src][/\h{40}/]).content
+      expect(file_js).to include(old_upload_url)
+
+      css_link_tag = Nokogiri::HTML5.fragment(
+        Stylesheet::Manager.new(theme_id: theme.id).stylesheet_link_tag(:desktop_theme, 'all')
+      ).css('link').first
+      css = StylesheetCache.find_by(digest: css_link_tag[:href][/\h{40}/]).content
+      expect(css).to include("url(#{old_upload_url})")
+
+      Discourse.clear_all_theme_cache!
+
+      head_tag_script = Nokogiri::HTML5.fragment(
+        Theme.lookup_field(theme.id, :desktop, "head_tag")
+      ).css('script').first
+      head_tag_js = JavascriptCache.find_by(digest: head_tag_script[:src][/\h{40}/]).content
+      expect(head_tag_js).to include(new_upload_url)
+
+      js_file_script = Nokogiri::HTML5.fragment(
+        Theme.lookup_field(theme.id, :extra_js, nil)
+      ).css('script').first
+      file_js = JavascriptCache.find_by(digest: js_file_script[:src][/\h{40}/]).content
+      expect(file_js).to include(new_upload_url)
+
+      css_link_tag = Nokogiri::HTML5.fragment(
+        Stylesheet::Manager.new(theme_id: theme.id).stylesheet_link_tag(:desktop_theme, 'all')
+      ).css('link').first
+      css = StylesheetCache.find_by(digest: css_link_tag[:href][/\h{40}/]).content
+      expect(css).to include("url(#{new_upload_url})")
+    end
+  end
 end