Update to Ruby 4.0.0.

.devcontainer/Dockerfile

@@ -1,5 +1,5 @@
 # Make sure RUBY_VERSION matches the Ruby version in .ruby-version
-ARG RUBY_VERSION=3.4.7
+ARG RUBY_VERSION=4.0.0
 FROM ghcr.io/rails/devcontainer/images/ruby:$RUBY_VERSION
 
 # Ensure binding is always 0.0.0.0

.ruby-version

@@ -1 +1 @@
-3.4.7
+4.0.0

Dockerfile

@@ -8,7 +8,7 @@
 # For a containerized dev environment, see Dev Containers: https://guides.rubyonrails.org/getting_started_with_devcontainer.html
 
 # Make sure RUBY_VERSION matches the Ruby version in .ruby-version
-ARG RUBY_VERSION=3.4.7
+ARG RUBY_VERSION=4.0.0
 
 FROM --platform=$BUILDPLATFORM docker.io/library/ruby:${RUBY_VERSION}-slim AS base
 

Gemfile.lock

@@ -80,9 +80,9 @@ GEM
     bcrypt_pbkdf (1.1.2)
     bigdecimal (4.0.1)
     bindex (0.8.1)
-    bootsnap (1.20.0)
+    bootsnap (1.20.1)
       msgpack (~> 1.2)
-    brakeman (7.1.1)
+    brakeman (7.1.2)
       racc
     builder (3.3.0)
     bundler-audit (0.9.3)
@@ -150,6 +150,7 @@ GEM
       net-smtp
     marcel (1.1.0)
     mini_mime (1.1.5)
+    mini_portile2 (2.8.9)
     minitest (6.0.0)
       prism (~> 1.5)
     msgpack (1.8.0)
@@ -168,6 +169,9 @@ GEM
       net-protocol
     net-ssh (7.3.0)
     nio4r (2.7.5)
+    nokogiri (1.18.10)
+      mini_portile2 (~> 2.8.2)
+      racc (~> 1.4)
     nokogiri (1.18.10-aarch64-linux-gnu)
       racc (~> 1.4)
     nokogiri (1.18.10-aarch64-linux-musl)
@@ -181,6 +185,7 @@ GEM
     parser (3.3.10.0)
       ast (~> 2.4.1)
       racc
+    pg (1.6.2)
     pg (1.6.2-aarch64-linux)
     pg (1.6.2-aarch64-linux-musl)
     pg (1.6.2-arm64-darwin)

README.md

@@ -12,7 +12,7 @@ The purpose of this example is to provide details as to how one would go about u
 
 - Rails 8.1.1 or newer
 
-- Ruby 3.4.7 or newer
+- Ruby 4.0.0 or newer
 
 Note: This tutorial was updated on macOS 26.1 (Tahoe). Docker Desktop is ony needed if you're following the `Docker Installation`.