Add username checker

Author: adrien1018

app/validators/username_convention_validator.rb

@@ -1,13 +1,14 @@
 class UsernameConventionValidator < ActiveModel::EachValidator
   def validate_each(record, field, value)
     unless value.blank?
-      unless Rails.configuration.x.settings.dig(:unicode_username)
-        record.errors.add field, "is not alphanumeric (letters, numbers, underscores or periods)" unless value =~ /^[[:alnum:]._-]+$/
-        record.errors.add field, "should start with a letter" unless value[0] =~ /[A-Za-z]/
-        record.errors.add field, "contains illegal characters" unless value.ascii_only?
+      if Rails.configuration.x.settings.dig(:unicode_username)
+        record.errors.add field, "contains illegal characters" if /[\/]/.match(value)
+      else
+        record.errors.add field, "is not alphanumeric (letters, numbers, underscores or periods)" unless /^[a-zA-Z0-9._\-]+$/.match(value)
+        record.errors.add field, "should start with a letter" unless /^[A-Za-z]/.match(value)
       end
       record.errors.add field, "is forbidden" if ['sign_in', 'sign_up'].include? value
-      record.errors.add field, "should not be purely numeric" if value =~ /^[0-9]+$/
+      record.errors.add field, "should not be purely numeric" if /^[0-9]+$/.match(value)
     end
   end
 end

lib/tasks/check_invalid_username.rake

@@ -0,0 +1,29 @@
+namespace :user do
+  desc "Check if there are accounts with invalid usernames"
+  task :check_invalid_username => :environment do
+    lst = User.where.not('username REGEXP ?', '^[A-Za-z][a-zA-Z0-9._\-]*$')
+    unless lst
+      puts 'There are no accounts with invalid usernames.'
+      return
+    end
+    breaking, lst = lst.partition{|x| /[\/]/.match(x.username) }
+    pure_numeric, lst = lst.partition{|x| /^[0-9]+$/.match(x.username) }
+    overriden, lst = lst.partition{|x| ['sign_in', 'sign_up'].include? x.username }
+    unless breaking.empty?
+      puts "Accounts that can cause crash when rendering (username containing /):"
+      breaking.each {|x| puts "User ID #{x.id}: #{x.username}" }
+    end
+    unless overriden.empty?
+      puts "Accounts whose user page will be unreachable (username colliding with existing endpoints):"
+      overriden.each {|x| puts "User ID #{x.id}: #{x.username}" }
+    end
+    unless pure_numeric.empty?
+      puts "Accounts that normally don't cause issues, but may override other's user page when visiting by /users/[user-id] (purely numeric usernames):"
+      pure_numeric.each {|x| puts "User ID #{x.id}: #{x.username}" }
+    end
+    unless lst.empty?
+      puts "Accounts that don't cause issues, but violates the default username policy:"
+      lst.each {|x| puts "User ID #{x.id}: #{x.username}" }
+    end
+  end
+end