FEATURE: Customizable rules and plugins for `PrettyText.markdown`.

This commit extends the options which can be passed to
`PrettyText.markdown` so that which Markdown-it rules and Discourse
Markdown plugins to be used when rendering a text can be customizable.
Currently, this extension is mainly used by plugins.

app/assets/javascripts/discourse/tests/unit/lib/pretty-text-test.js

@@ -1493,6 +1493,45 @@ var bar = 'bar';
     );
   });
 
+  test("customizing markdown-it rules", function (assert) {
+    assert.cookedOptions(
+      "**bold**",
+      { markdownItRules: [] },
+      "<p>**bold**</p>",
+      "does not apply bold markdown when rule is not enabled"
+    );
+
+    assert.cookedOptions(
+      "**bold**",
+      { markdownItRules: ["emphasis"] },
+      "<p><strong>bold</strong></p>",
+      "applies bold markdown when rule is enabled"
+    );
+  });
+
+  test("features override", function (assert) {
+    assert.cookedOptions(
+      ":grin: @sam",
+      { featuresOverride: [] },
+      "<p>:grin: @sam</p>",
+      "does not cook emojis when Discourse markdown engines are disabled"
+    );
+
+    assert.cookedOptions(
+      ":grin: @sam",
+      { featuresOverride: ["emoji"] },
+      '<p><img src="/images/emoji/google_classic/grin.png?v=10" title=":grin:" class="emoji" alt=":grin:"> @sam</p>',
+      "cooks emojis when only the emoji markdown engine is enabled"
+    );
+
+    assert.cookedOptions(
+      ":grin: @sam",
+      { featuresOverride: ["mentions", "text-post-process"] },
+      `<p>:grin: <span class="mention">@sam</span></p>`,
+      "cooks mentions when only the mentions markdown engine is enabled"
+    );
+  });
+
   test("emoji", function (assert) {
     assert.cooked(
       ":smile:",

app/assets/javascripts/pretty-text/addon/engines/discourse-markdown-it.js

@@ -353,6 +353,12 @@ export function setup(opts, siteSettings, state) {
     }
   });
 
+  if (opts.featuresOverride) {
+    Object.keys(opts.features).forEach((feature) => {
+      opts.features[feature] = opts.featuresOverride.includes(feature);
+    });
+  }
+
   let copy = {};
   Object.keys(opts).forEach((entry) => {
     copy[entry] = opts[entry];
@@ -371,14 +377,22 @@ export function setup(opts, siteSettings, state) {
     enableDiffhtmlPreview: siteSettings.enable_diffhtml_preview,
   };
 
-  opts.engine = window.markdownit({
+  const markdownitOpts = {
     discourse: opts.discourse,
     html: true,
     breaks: !siteSettings.traditional_markdown_linebreaks,
     xhtmlOut: false,
     linkify: siteSettings.enable_markdown_linkify,
     typographer: siteSettings.enable_markdown_typographer,
-  });
+  };
+
+  if (opts.discourse.markdownItRules !== undefined) {
+    opts.engine = window
+      .markdownit("zero", markdownitOpts) // Preset for "zero", https://github.com/markdown-it/markdown-it/blob/master/lib/presets/zero.js
+      .enable(opts.discourse.markdownItRules);
+  } else {
+    opts.engine = window.markdownit(markdownitOpts);
+  }
 
   const quotation_marks = siteSettings.markdown_typographer_quotation_marks;
   if (quotation_marks) {

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

@@ -38,6 +38,8 @@ export function buildOptions(state) {
     customEmojiTranslation,
     watchedWordsReplace,
     watchedWordsLink,
+    featuresOverride,
+    markdownItRules,
   } = state;
 
   let features = {};
@@ -76,6 +78,8 @@ export function buildOptions(state) {
     disableEmojis,
     watchedWordsReplace,
     watchedWordsLink,
+    featuresOverride,
+    markdownItRules,
   };
 
   // note, this will mutate options due to the way the API is designed

lib/pretty_text.rb

@@ -156,6 +156,17 @@ module PrettyText
     end
   end
 
+  # Acceptable options:
+  #
+  #  disable_emojis    - Disables the emoji markdown engine.
+  #  features          - A hash where the key is the markdown feature name and the value is a boolean to enable/disable the markdown feature.
+  #                      The hash is merged into the default features set in pretty-text.js which can be used to add new features or disable existing features.
+  #  features_override - An array of markdown feature names to override the default markdown feature set. Currently used by plugins to customize what features should be enabled
+  #                      when rendering markdown.
+  #  markdown_it_rules - An array of markdown rule names which will be applied to the markdown-it engine. Currently used by plugins to customize what markdown-it rules should be
+  #                      enabled when rendering markdown.
+  #  topic_id          - Topic id for the post being cooked.
+  #  user_id           - User id for the post being cooked.
   def self.markdown(text, opts = {})
     # we use the exact same markdown converter as the client
     # TODO: use the same extensions on both client and server (in particular the template for mentions)
@@ -175,6 +186,8 @@ module PrettyText
         __paths = #{paths_json};
         __optInput.getURL = __getURL;
         #{"__optInput.features = #{opts[:features].to_json};" if opts[:features]}
+        #{"__optInput.featuresOverride = #{opts[:features_override].to_json};" if opts[:features_override]}
+        #{"__optInput.markdownItRules = #{opts[:markdown_it_rules].to_json};" if opts[:markdown_it_rules]}
         __optInput.getCurrentUser = __getCurrentUser;
         __optInput.lookupAvatar = __lookupAvatar;
         __optInput.lookupPrimaryUserGroup = __lookupPrimaryUserGroup;
@@ -190,8 +203,8 @@ module PrettyText
         __optInput.watchedWordsLink = #{WordWatcher.word_matcher_regexps(:link).to_json};
       JS
 
-      if opts[:topicId]
-        buffer << "__optInput.topicId = #{opts[:topicId].to_i};\n"
+      if opts[:topic_id]
+        buffer << "__optInput.topicId = #{opts[:topic_id].to_i};\n"
       end
 
       if opts[:user_id]
@@ -279,10 +292,6 @@ module PrettyText
 
   def self.cook(text, opts = {})
     options = opts.dup
-
-    # we have a minor inconsistency
-    options[:topicId] = opts[:topic_id]
-
     working_text = text.dup
 
     sanitized = markdown(working_text, options)

spec/components/pretty_text_spec.rb

@@ -2072,4 +2072,32 @@ HTML
 
     expect(cooked).to match_html(html)
   end
+
+  context "customizing markdown-it rules" do
+    it 'customizes the markdown-it rules correctly' do
+      cooked = PrettyText.cook('This is some text **bold**', markdown_it_rules: [])
+
+      expect(cooked).to eq("<p>This is some text **bold**</p>")
+
+      cooked = PrettyText.cook('This is some text **bold**', markdown_it_rules: ["emphasis"])
+
+      expect(cooked).to eq("<p>This is some text <strong>bold</strong></p>")
+    end
+  end
+
+  context "enabling/disabling features" do
+    it "allows features to be overriden" do
+      cooked = PrettyText.cook(':grin: @mention', features_override: [])
+
+      expect(cooked).to eq("<p>:grin: @mention</p>")
+
+      cooked = PrettyText.cook(':grin: @mention', features_override: ["emoji"])
+
+      expect(cooked).to eq("<p><img src=\"/images/emoji/twitter/grin.png?v=10\" title=\":grin:\" class=\"emoji\" alt=\":grin:\"> @mention</p>")
+
+      cooked = PrettyText.cook(':grin: @mention', features_override: ["mentions", "text-post-process"])
+
+      expect(cooked).to eq("<p>:grin: <span class=\"mention\">@mention</span></p>")
+    end
+  end
 end