DEV: Support inverted guardian predicate methods

lib/guardian.rb

@@ -96,6 +96,21 @@ class Guardian
     end
   end
 
+  # Support `cannot_do?` as an alias of `if !can_do?` and `unless can_do?`.
+  def method_missing(name, *arguments)
+    prefix, check = name.to_s.split("_", 2)
+
+    if prefix == "cannot"
+      !send("can_#{check}", *arguments)
+    else
+      super
+    end
+  end
+
+  def respond_to_missing?(name)
+    name.to_s.start_with?("cannot_") || super
+  end
+
   attr_reader :request
 
   def initialize(user = nil, request = nil)
@@ -188,7 +203,7 @@ class Guardian
     # can_create_klass_on_parent?
     target = klass.name.underscore
     if parent.present?
-      return false unless can_see?(parent)
+      return false if cannot_see?(parent)
       target << "_on_#{parent.class.name.underscore}"
     end
     create_method = :"can_create_#{target}?"
@@ -605,7 +620,7 @@ class Guardian
     return false if SiteSetting.secure_uploads?
     return false if topic.blank?
     return false if topic.private_message?
-    return false unless can_see_topic?(topic)
+    return false if cannot_see_topic?(topic)
     is_staff?
   end
 

lib/guardian/ensure_magic.rb

@@ -19,6 +19,6 @@ module EnsureMagic
 
   # Make sure we can see the object. Will raise a NotFound if it's nil
   def ensure_can_see!(obj)
-    raise Discourse::InvalidAccess.new("Can't see #{obj}") unless can_see?(obj)
+    raise Discourse::InvalidAccess.new("Can't see #{obj}") if cannot_see?(obj)
   end
 end

lib/guardian/post_guardian.rb

@@ -217,7 +217,7 @@ module PostGuardian
   end
 
   def can_delete_post?(post)
-    return false if !can_see_post?(post)
+    return false if cannot_see_post?(post)
 
     # Can't delete the first post
     return false if post.is_first_post?
@@ -247,7 +247,7 @@ module PostGuardian
     return false if !SiteSetting.can_permanently_delete
     return false if !post
     return false if post.is_first_post?
-    return false if !is_admin? || !can_edit_post?(post)
+    return false if !is_admin? || cannot_edit_post?(post)
     return false if !post.deleted_at
     if post.deleted_by_id == @user.id && post.deleted_at >= Post::PERMANENT_DELETE_TIMER.ago
       return false
@@ -310,7 +310,7 @@ module PostGuardian
   def can_see_post?(post)
     return false if post.blank?
     return true if is_admin?
-    return false unless can_see_post_topic?(post)
+    return false if cannot_see_post_topic?(post)
     unless post.user == @user || Topic.visible_post_types(@user).include?(post.post_type)
       return false
     end

lib/guardian/post_revision_guardian.rb

@@ -4,7 +4,7 @@
 module PostRevisionGuardian
   def can_see_post_revision?(post_revision)
     return false unless post_revision
-    return false if post_revision.hidden && !can_view_hidden_post_revisions?
+    return false if post_revision.hidden && cannot_view_hidden_post_revisions?
 
     can_view_edit_history?(post_revision.post)
   end

lib/guardian/topic_guardian.rb

@@ -90,7 +90,7 @@ module TopicGuardian
   # Editing Method
   def can_edit_topic?(topic)
     return false if Discourse.static_doc_topic_ids.include?(topic.id) && !is_admin?
-    return false unless can_see?(topic)
+    return false if cannot_see?(topic)
 
     first_post = topic.first_post
 
@@ -107,7 +107,7 @@ module TopicGuardian
          SiteSetting.allow_uncategorized_topics ||
            topic.category_id != SiteSetting.uncategorized_category_id
        )
-      return false if !can_create_topic_on_category?(topic.category)
+      return false if cannot_create_topic_on_category?(topic.category)
     end
 
     # Editing a shared draft.
@@ -186,7 +186,7 @@ module TopicGuardian
         .count
     return false if all_posts_count > 1
 
-    return false if !is_admin? || !can_see_topic?(topic)
+    return false if !is_admin? || cannot_see_topic?(topic)
     return false if !topic.deleted_at
     if topic.deleted_by_id == @user.id && topic.deleted_at >= Post::PERMANENT_DELETE_TIMER.ago
       return false
@@ -247,7 +247,7 @@ module TopicGuardian
     end
 
     # Filter out topics with shared drafts if user cannot see shared drafts
-    if !can_see_shared_draft?
+    if cannot_see_shared_draft?
       default_scope =
         default_scope.left_outer_joins(:shared_draft).where("shared_drafts.id IS NULL")
     end
@@ -269,13 +269,13 @@ module TopicGuardian
   def can_see_topic?(topic, hide_deleted = true)
     return false unless topic
     return true if is_admin? && !SiteSetting.suppress_secured_categories_from_admin
-    return false if hide_deleted && topic.deleted_at && !can_see_deleted_topics?(topic.category)
+    return false if hide_deleted && topic.deleted_at && cannot_see_deleted_topics?(topic.category)
 
     if topic.private_message?
       return authenticated? && topic.all_allowed_users.where(id: @user.id).exists?
     end
 
-    return false if topic.shared_draft && !can_see_shared_draft?
+    return false if topic.shared_draft && cannot_see_shared_draft?
 
     category = topic.category
     can_see_category?(category) &&
@@ -327,8 +327,8 @@ module TopicGuardian
   end
 
   def can_edit_tags?(topic)
-    return false unless can_tag_topics?
-    return false if topic.private_message? && !can_tag_pms?
+    return false if cannot_tag_topics?
+    return false if topic.private_message? && cannot_tag_pms?
     return true if can_edit_topic?(topic)
 
     if topic&.first_post&.wiki &&
@@ -355,7 +355,7 @@ module TopicGuardian
 
   def can_move_posts?(topic)
     return false if is_silenced?
-    return false unless can_perform_action_available_to_group_moderators?(topic)
+    return false if cannot_perform_action_available_to_group_moderators?(topic)
     return false if topic.archetype == "private_message" && !is_staff?
     true
   end

lib/guardian/user_guardian.rb

@@ -102,7 +102,7 @@ module UserGuardian
   end
 
   def restrict_user_fields?(user)
-    (user.trust_level == TrustLevel[0] && anonymous?) || !can_see_profile?(user)
+    (user.trust_level == TrustLevel[0] && anonymous?) || cannot_see_profile?(user)
   end
 
   def can_see_staff_info?(user)