From 3360f91733a3aaba670c55427f9195da9c02d981 Mon Sep 17 00:00:00 2001
From: Tom Hughes <tom@compton.nu>
Date: Sun, 25 Feb 2024 13:16:40 +0000
Subject: [PATCH] Require display names to have a minimum unicode width of 3
 columns

Fixes #4538
---
 .rubocop_todo.yml                 |  2 +-
 Gemfile                           |  3 +++
 Gemfile.lock                      |  1 +
 app/models/user.rb                |  3 ++-
 app/validators/width_validator.rb | 11 +++++++++++
 test/models/user_test.rb          | 12 ++++++++++++
 6 files changed, 30 insertions(+), 2 deletions(-)
 create mode 100644 app/validators/width_validator.rb

diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 6c917e218..fdc7c35a5 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -66,7 +66,7 @@ Metrics/BlockNesting:
 # Offense count: 26
 # Configuration parameters: CountComments, CountAsOne.
 Metrics/ClassLength:
-  Max: 313
+  Max: 314
 
 # Offense count: 59
 # Configuration parameters: AllowedMethods, AllowedPatterns.
diff --git a/Gemfile b/Gemfile
index 63d9c49e8..832b96c9a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -136,6 +136,9 @@ gem "aws-sdk-s3"
 # Used to resize user images
 gem "image_processing"
 
+# Used to validate widths
+gem "unicode-display_width"
+
 # Gems useful for development
 group :development do
   gem "better_errors"
diff --git a/Gemfile.lock b/Gemfile.lock
index 24beeb4d1..234090689 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -683,6 +683,7 @@ DEPENDENCIES
   sprockets-exporters_pack
   strong_migrations
   terser
+  unicode-display_width
   validates_email_format_of (>= 1.5.1)
   vendorer
   webmock
diff --git a/app/models/user.rb b/app/models/user.rb
index 6fa0f330e..125e5e973 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -98,7 +98,8 @@ class User < ApplicationRecord
                            :normalized_uniqueness => { :case_sensitive => false }
   validates :display_name, :if => proc { |u| u.display_name_changed? },
                            :characters => { :url_safe => true },
-                           :whitespace => { :leading => false, :trailing => false }
+                           :whitespace => { :leading => false, :trailing => false },
+                           :width => { :minimum => 3 }
   validate :display_name_cannot_be_user_id_with_other_id, :if => proc { |u| u.display_name_changed? }
   validates :email, :presence => true, :confirmation => true, :characters => true
   validates :email, :if => proc { |u| u.email_changed? },
diff --git a/app/validators/width_validator.rb b/app/validators/width_validator.rb
new file mode 100644
index 000000000..a3a4d414c
--- /dev/null
+++ b/app/validators/width_validator.rb
@@ -0,0 +1,11 @@
+class WidthValidator < ActiveModel::Validations::LengthValidator
+  module WidthAsLength
+    def length
+      Unicode::DisplayWidth.of(to_s)
+    end
+  end
+
+  def validate_each(record, attribute, value)
+    super(record, attribute, value.extend(WidthAsLength))
+  end
+end
diff --git a/test/models/user_test.rb b/test/models/user_test.rb
index 42949504f..92e7d419c 100644
--- a/test/models/user_test.rb
+++ b/test/models/user_test.rb
@@ -67,6 +67,18 @@ class UserTest < ActiveSupport::TestCase
     assert_not_predicate user, :valid?, "should not allow nil value"
   end
 
+  def test_display_name_width
+    user = build(:user)
+    user.display_name = "123"
+    assert_predicate user, :valid?, "should allow 3 column name name"
+    user.display_name = "12"
+    assert_not_predicate user, :valid?, "should not allow 2 column name"
+    user.display_name = "1\u{200B}2"
+    assert_not_predicate user, :valid?, "should not allow 2 column name"
+    user.display_name = "\u{200B}\u{200B}\u{200B}"
+    assert_not_predicate user, :valid?, "should not allow 0 column name"
+  end
+
   def test_display_name_valid
     # Due to sanitisation in the view some of these that you might not
     # expect are allowed
-- 
2.39.5