DEV: Add markdown_additional_options to Site (#15738)

Sometimes plugins need to have additional data or options available
when rendering custom markdown features/rules that are not available
on the default opts.discourse object. These additional options should
be namespaced to the plugin adding them.

```
Site.markdown_additional_options["chat"] = { limited_pretty_text_markdown_rules: [] }
```

These are passed down to markdown rules on opts.discourse.additionalOptions.

The main motivation for adding this is the chat plugin, which currently stores
chat_pretty_text_features and chat_pretty_text_markdown_rules on
the Site object via additions to the serializer, and the Site object is
not accessible to import via markdown rules (either through
Site.current() or through container.lookup). So, to have this working
for both front + backend code, we need to attach these additional options
from the Site object onto the markdown options object.

app/assets/javascripts/discourse/app/lib/text.js

@@ -23,6 +23,7 @@ function getOpts(opts) {
       formatUsername,
       watchedWordsReplace: context.site.watched_words_replace,
       watchedWordsLink: context.site.watched_words_link,
+      additionalOptions: context.site.markdown_additional_options,
     },
     opts
   );

app/assets/javascripts/pretty-text/addon/pretty-text.js

@@ -40,6 +40,7 @@ export function buildOptions(state) {
     watchedWordsLink,
     featuresOverride,
     markdownItRules,
+    additionalOptions,
   } = state;
 
   let features = {};
@@ -80,6 +81,7 @@ export function buildOptions(state) {
     watchedWordsLink,
     featuresOverride,
     markdownItRules,
+    additionalOptions,
   };
 
   // note, this will mutate options due to the way the API is designed

app/models/site.rb

@@ -7,6 +7,20 @@ class Site
   cattr_accessor :preloaded_category_custom_fields
   self.preloaded_category_custom_fields = Set.new
 
+  ##
+  # Sometimes plugins need to have additional data or options available
+  # when rendering custom markdown features/rules that are not available
+  # on the default opts.discourse object. These additional options should
+  # be namespaced to the plugin adding them.
+  #
+  # ```
+  # Site.markdown_additional_options["chat"] = { limited_pretty_text_markdown_rules: [] }
+  # ```
+  #
+  # These are passed down to markdown rules on opts.discourse.additionalOptions.
+  cattr_accessor :markdown_additional_options
+  self.markdown_additional_options = {}
+
   def self.add_categories_callbacks(&block)
     categories_callbacks << block
   end

app/serializers/site_serializer.rb

@@ -32,7 +32,8 @@ class SiteSerializer < ApplicationSerializer
     :custom_emoji_translation,
     :watched_words_replace,
     :watched_words_link,
-    :categories
+    :categories,
+    :markdown_additional_options
   )
 
   has_many :archetypes, embed: :objects, serializer: ArchetypeSerializer
@@ -203,6 +204,10 @@ class SiteSerializer < ApplicationSerializer
     object.categories.map { |c| c.to_h }
   end
 
+  def markdown_additional_options
+    Site.markdown_additional_options
+  end
+
   private
 
   def ordered_flags(flags)

lib/pretty_text.rb

@@ -201,6 +201,7 @@ module PrettyText
         __optInput.censoredRegexp = #{WordWatcher.word_matcher_regexp(:censor)&.source.to_json};
         __optInput.watchedWordsReplace = #{WordWatcher.word_matcher_regexps(:replace).to_json};
         __optInput.watchedWordsLink = #{WordWatcher.word_matcher_regexps(:link).to_json};
+        __optInput.additionalOptions = #{Site.markdown_additional_options.to_json};
       JS
 
       if opts[:topic_id]

spec/requests/api/schemas/json/site_response.json

@@ -466,6 +466,9 @@
         "null"
       ]
     },
+    "markdown_additional_options" : {
+      "type": "object"
+    },
     "categories": {
       "type": "array",
       "items": [