Moving from CoffeeScript to ES6 is straightforward with decaffeinate, which converts .coffee files to modern JavaScript and may need manual cleanup afterward.

return inside a block can replace a method’s own result and skip later code, which can break Rails helpers like capture and lose html_safe? information.

A too-small /boot partition can block updates; switching initramfs compression to xz may shrink boot images without resizing the partition.

Ruby 2.6 adds Proc and Method composition, making functional-style chaining possible in Ruby code.

Using window.jQuery in ProvidePlugin can leave jQuery undefined in the browser while $ still works; assigning through global avoids the conflict.

Updating rows from a related table is needed when backfilling cached data. PostgreSQL and MySQL use different UPDATE join syntax for copying associated values.

PostCSS plugin output can be verified by compiling assets and checking Autoprefixer and CSS feature transforms from postcss-preset-env.

HTML emails often break when mail clients ignore external stylesheets. premailer-rails inlines CSS for Rails mailers, and inline image attachments improve compatibility.

Moving a Rails app from the Asset Pipeline to Webpacker requires inventorying bundled libraries, repackaging legacy assets, and adjusting deployment for pack-based assets.

Rails migration column sizes depend on type: :limit controls bytes or characters, and certain values map to MySQL tinyint, smallint, mediumint, bigint, text, mediumtext, or longtext.

Hidden and lesser-known Git and GitHub features can speed up everyday workflows and reduce friction for version control and collaboration.

Deployment can fail with a misleading Gemfile error when the server uses a newer Bundler than the version recorded in Gemfile.lock. Matching Bundler major versions on both sides prevents the install mismatch.

Timezone abbreviations are ambiguous and often unsupported in Rails time handling; ActiveSupport zone names and offsets avoid wrong parsing, DST mistakes, and misleading displays.

Reverting creates a new commit that undoes earlier changes, useful for backing out a single change or several related commits without rewriting history.

Flex items can overflow small screens because min-width:auto prevents shrinking below content size; min-width: 0 lets them fit available space.

Using self-hosted or purchased fonts with Webpack or Webpacker requires either bundling them from assets or packaging them locally for clean imports.

valid? no longer changes a record's state in rails_state_machine 1.1.2, preventing validation checks from causing unintended transitions.

Parallel test runs can exceed Redis’s default 16 databases on multi-core machines, causing ERR DB index is out of range; increasing the database limit resolves it.