FIX: Reintroduce auto_silence_first_post_regex (#12223)

Follow-up to 533800a87b.

config/locales/server.en.yml

@@ -1942,6 +1942,7 @@ en:
     min_first_post_typing_time: "Minimum amount of time in milliseconds a user must type during first post, if threshold is not met post will automatically enter the needs approval queue. Set to 0 to disable (not recommended)"
     auto_silence_fast_typers_on_first_post: "Automatically silence users that do not meet min_first_post_typing_time"
     auto_silence_fast_typers_max_trust_level: "Maximum trust level to auto silence fast typers"
+    auto_silence_first_post_regex: "Case insensitive regex that if passed will cause first post by user to be silenced and sent to approval queue. Example: raging|a[bc]a , will cause all posts containing raging or aba or aca to be silenced on first. Only applies to first post."
     reviewable_claiming: "Does reviewable content need to be claimed before it can be acted upon?"
     reviewable_default_topics: "Show reviewable content grouped by topic by default"
     reviewable_default_visibility: "Don't show reviewable items unless they meet this priority"
@@ -4903,6 +4904,7 @@ en:
       trust_level: "Users at low trust levels must have replies approved by staff. See `approve_unless_trust_level`."
       new_topics_unless_trust_level: "Users at low trust levels must have topics approved by staff. See `approve_new_topics_unless_trust_level`."
       fast_typer: "New user typed their first post suspiciously fast, suspected bot or spammer behavior. See `min_first_post_typing_time`."
+      auto_silence_regexp: "New user whose first post matches the `auto_silence_first_post_regex` setting."
       watched_word: "This post included a Watched Word. See your <a href='%{base_url}/admin/logs/watched_words'>list of watched words</a>."
       staged: "New topics and posts for staged users must be approved by staff. See `approve_unless_staged`."
       category: "Posts in this category require manual approval by staff. See the category settings."

config/site_settings.yml

@@ -1660,6 +1660,7 @@ spam:
   min_first_post_typing_time: 3000
   auto_silence_fast_typers_on_first_post: true
   auto_silence_fast_typers_max_trust_level: 0
+  auto_silence_first_post_regex: ""
   high_trust_flaggers_auto_hide_posts: true
   cooldown_hours_until_reflag:
     default: 24

db/migrate/20210204190020_move_auto_silence_first_post_regex_to_watched_words.rb

@@ -1,24 +0,0 @@
-# frozen_string_literal: true
-
-class MoveAutoSilenceFirstPostRegexToWatchedWords < ActiveRecord::Migration[6.0]
-  def up
-    execute <<~SQL
-      INSERT INTO watched_words (word, action, created_at, updated_at)
-      SELECT value, 3, created_at, updated_at
-      FROM site_settings
-      WHERE name = 'auto_silence_first_post_regex'
-      ON CONFLICT DO NOTHING
-    SQL
-
-    execute <<~SQL
-      INSERT INTO watched_words (word, action, created_at, updated_at)
-      SELECT unnest(string_to_array(value, '|')), 3, created_at, updated_at
-      FROM site_settings
-      WHERE name = 'auto_silence_first_post_regex'
-      ON CONFLICT DO NOTHING
-    SQL
-  end
-
-  def down
-  end
-end

lib/new_post_manager.rb

@@ -54,6 +54,25 @@ class NewPostManager
     manager.user.trust_level <= SiteSetting.auto_silence_fast_typers_max_trust_level
   end
 
+  def self.matches_auto_silence_regex?(manager)
+    args = manager.args
+
+    pattern = SiteSetting.auto_silence_first_post_regex
+
+    return false unless pattern.present?
+    return false unless is_first_post?(manager)
+
+    begin
+      regex = Regexp.new(pattern, Regexp::IGNORECASE)
+    rescue => e
+      Rails.logger.warn "Invalid regex in auto_silence_first_post_regex #{e}"
+      return false
+    end
+
+    "#{args[:title]} #{args[:raw]}" =~ regex
+
+  end
+
   def self.exempt_user?(user)
     user.staff?
   end
@@ -83,6 +102,8 @@ class NewPostManager
 
     return :fast_typer if is_fast_typer?(manager)
 
+    return :auto_silence_regex if matches_auto_silence_regex?(manager)
+
     return :staged if SiteSetting.approve_unless_staged? && user.staged?
 
     return :category if post_needs_approval_in_its_category?(manager)
@@ -147,6 +168,8 @@ class NewPostManager
     I18n.with_locale(SiteSetting.default_locale) do
       if is_fast_typer?(manager)
         UserSilencer.silence(manager.user, Discourse.system_user, keep_posts: true, reason: I18n.t("user.new_user_typed_too_fast"))
+      elsif matches_auto_silence_regex?(manager)
+        UserSilencer.silence(manager.user, Discourse.system_user, keep_posts: true, reason: I18n.t("user.content_matches_auto_silence_regex"))
       elsif reason == :email_spam && is_first_post?(manager)
         UserSilencer.silence(manager.user, Discourse.system_user, keep_posts: true, reason: I18n.t("user.email_in_spam_header"))
       end

spec/requests/posts_controller_spec.rb

@@ -857,6 +857,26 @@ describe PostsController do
         end
       end
 
+      it 'silences correctly based on auto_silence_first_post_regex' do
+        SiteSetting.auto_silence_first_post_regex = "I love candy|i eat s[1-5]"
+
+        post "/posts.json", params: {
+          raw: 'this is the test content',
+          title: 'when I eat s3 sometimes when not looking'
+        }
+
+        expect(response.status).to eq(200)
+        parsed = response.parsed_body
+
+        expect(parsed["action"]).to eq("enqueued")
+        reviewable = ReviewableQueuedPost.find_by(created_by: user)
+        score = reviewable.reviewable_scores.first
+        expect(score.reason).to eq('auto_silence_regex')
+
+        user.reload
+        expect(user).to be_silenced
+      end
+
       it "can send a message to a group" do
         group = Group.create(name: 'test_group', messageable_level: Group::ALIAS_LEVELS[:nobody])
         user1 = user