What causes "DEPRECATION WARNING: #{message} (called from #{offending_line})" in mislav/will_paginate?

Open the file:line printed in '(called from ...)' and migrate that call to the replacement named in the message

DEPRECATION WARNING: #{message} (called from #{offending_lin

Error message

DEPRECATION WARNING: #{message} (called from #{offending_line})

What it means

WillPaginate::Deprecation.warn is not a raised exception but the gem's deprecation channel: it formats 'DEPRECATION WARNING: <message> (called from <file:line>)' using origin_of_call(caller) and writes it to Rails.logger when defined, else falls back to Kernel#warn (stderr). Seeing it means the library detected you using an API scheduled for removal and pinpointed the exact call site.

Source

Thrown at lib/will_paginate/deprecation.rb:3

module WillPaginate::Deprecation
  class << self
    def warn(message, stack = caller)
      offending_line = origin_of_call(stack)
      full_message = "DEPRECATION WARNING: #{message} (called from #{offending_line})"
      logger = rails_logger || Kernel
      logger.warn full_message
    end

    private

    def rails_logger
      defined?(Rails.logger) && Rails.logger
    end

    def origin_of_call(stack)
      lib_root = File.expand_path('../../..', __FILE__)
      stack.find { |line| line.index(lib_root) != 0 } || stack.first
    end
  end

View on GitHub (pinned to 50017c3eb0)

Solutions

Open the file:line printed in '(called from ...)' and migrate that call to the replacement named in the message
Triage in bulk: grep the test suite output for 'DEPRECATION WARNING:' lines mentioning will_paginate and fix each unique call site
Temporarily silence noise by routing logs, but never ship the deprecated call past the next major upgrade

Example fix

// before
# log: DEPRECATION WARNING: ... (called from app/models/post.rb:8:in `old_style')
class Post < ActiveRecord::Base
  def old_style
    WillPaginate::Collection.new(1, 10) # deprecated call at post.rb:8
  end
end

// after
class Post < ActiveRecord::Base
  def old_style
    page(1).per(10) # current scope-based API
  end
end

Defensive patterns

Strategy: validation

Validate before calling

# make deprecations fail specs instead of scrolling past (config/environments/test.rb)
WillPaginate::Deprecation.singleton_class.prepend(Module.new do
  def warn(message, stack = caller)
    raise "WillPaginate deprecation: #{message} (called from #{WillPaginate::Deprecation.send(:origin_of_call, stack)})"
  end
end)

Prevention

Promote will_paginate deprecation warnings to test failures (snippet above) so each one is fixed at the call site it names
After upgrading will_paginate or Rails, grep logs for 'DEPRECATION WARNING' lines with '(called from ...)' and burn them down before the next major bump
Pin the gem version in the Gemfile and read its CHANGELOG before upgrading to learn which deprecated APIs become hard errors

When it happens

Trigger: Any library-internal WillPaginate::Deprecation.warn call — typically legacy API usage detected during gem upgrade paths (old option names, removed class methods, changed signatures). The '(called from ...)' suffix names the file and line in your app that triggered it, since caller frames are captured at warn time.

Common situations: Bumping will_paginate after a Rails upgrade and logs flooding with deprecations; CI logs where Kernel fallback prints to stderr because Rails.logger isn't defined yet (e.g., during boot/initializers); teams ignoring warnings until the next major version turns them into hard errors.

Related errors

AI-assisted analysis of mislav/will_paginate@50017c3eb0 (2026-08-21). Data as JSON: /api/errors/46ab6c01645a17ca. Report an issue: GitHub.