Warning Signs ⚠️⚠️

The Warning Signs gem builds upon the ideas of the Ruby Warning Gem and Stop ignoring your Rails (and Ruby) deprecations!.

The idea is to provide an easily-configurable way to manage deprecation warnings from Ruby and Rails to support your upgrades.

Installing Warning Signs

To install Warning Signs add

gem "warning_signs"

to your gemfile, you will most likely want it to be in all environments, but under some use cases, you may not need it in production.

Using Warning Signs

The Warning Signs gem looks for a .warning_signs.yml file when the Rails application starts. If it does not find the file, it will not load and the processing of deprecations will be unaffected.

You should remove any environment settings in Rails that are managing config.active_support.deprecation, or at least those that are not set to :notify -- use WarningSigns to handle those settings...

Handlers

Warning Signs allows you to define handlers in the YAML file. A handler consists of the following:

  • Patterns to match, which can be specified with only to match the patterns specified and no others, or with except to match all patterns except the given ones. If no patterns are specified, all patterns match.
  • A source, either ruby for deprecations triggered with Ruby's Warn module, or rails for deprecations triggered with Rails' ActiveSupport::Deprecation. If a source is not specified, the handler matches both sources.
  • Environments and behaviors. An environment is either the name of a Rails environment, the special word all which matches all environments, or the special word other, which matches any environment not specifically
    invoked.
  • Each environment can specify one or more behaviors:
    • log sends a message to the Rails logger
    • stderr sends a message to the standard error stream
    • raise raises an exception
    • ignore does nothing

Handlers are matched in order. If no handler applies to a deprecation warning, Ruby warnings is ignored, Rails warnings are passed through the ActiveSupport notification mechanism.

The following example logs all deprecation warnings:

handlers:
  - environment: all
    behavior: log

Environments

Multiple environments need to be handled in a nested list. This example raises exceptions in the test environment, but logs in other environments

handlers:
  - environments:
      - environment: test
        behavior: raise
      - environment: other
        behavior: log

Sources

This example raises exceptions for Ruby deprecations, but ignores Rails deprecations:

handlers:
  - source: ruby
    environment: all
    behavior: raise
  - source: rails
    environment: all
    behavior: ignore

A single environment can have multiple behaviors. This is helpful if you are, say dealing with end-to-end specs that swallow exceptions:

handlers:
  - environment: all
    behaviors: 
      - raise
      - log

No matter what order you have the behaviors in, a raise behavior will be executed last so that the other behaviors happen before the exception is invoked.

Message Formatters

Message formatters can affect how and what data is passed to the output channel. You can define one handler:

handlers:
  - environment: all
    behavior: log
    message_formatter:
      backtrace_lines: 3
      format: hash
      filter_backtrace: filter_internals

There are a few attributes of message formatter that you can set

  • backtrace_lines is the number of filtered lines of backtrace, after the current line, that are sent to the output. The default is zero. (For raising exceptions, the default is the entire backtrace).
  • format can be text, json, hash, or yaml. Non text formats are hashes with keys message and backtrace, with the json and yaml formats converted to strings in those formats.
  • filter_backtrace has three settings. The default is yes, which filters out Ruby internals, references to warning signs itself, and lines from gems. To not filter at all, say no. To filter internals but not gems, say filter_internals.

If a message formatter is not specified, the default is a hash with zero backtrace lines.

Or you can define multiple message formatters. These can separate format based on output behavior.

In this example, log behaviors are sent in hash format, while stderr behaviors are sent in text format. Instead of an only list, an except list can be specified.

handlers:
  - environment: all
    behaviors:
      - log
      - stderr
      - raise
    message_formatters:
      - backtrace_lines: 3
        format: hash
        behaviors:
          only:
            - log
      - backtrace_lines: 3
        format: text
        behaviors:
          only:
            - stderr

You can also define multiple message formatters based on environment.

In this case, logs in production get hash format, while logs in development get yaml format.

handlers:
  - environment: all
    behaviors:
      - log
    message_formatters:
      - backtrace_lines: 3
        format: hash
        environments:
          only:
            - production
      - backtrace_lines: 3
        format: yaml
        environments:
          only:
            - development

Environments can also be listed negatively with except.

Environment and behavior matching can be used together.

If no message formatter matches a given message, the default is text format with no backtrace lines.

Pattern Matching

A common pattern is to focus only on specific deprecations and ignore others. For example, this setting file would raise on Ruby keyword argument deprecations and ignore other ruby deprecations

handlers:
  - source: ruby
    only:
      - "Using the last argument as keyword parameters is deprecated"
      - "Passing the keyword argument as the last hash parameter is deprecated"
      - "Splitting the last argument into positional and keyword parameters is deprecated"
    environment: all
    behavior: log

Patterns are matched if the deprecation message contains the pattern as a substring.

The pattern can be a regular expression, denoted by using regular expression syntax inside the string in the YAML:

handlers:
  - source: ruby
    only:
      - "/Using .* argument/"
    environment: all
    behavior: log

The pattern inside the slashes is converted to a Ruby Regexp and patterns are matched if the regexp and the deprecation warning message match.

Another pattern is to have a list of ignored deprecations and then remove messages one by one and manage them individually.

In this case, the except pattern is used to excuse those known patterns from the list. Other patterns will raise in test, or log in other environments. 

handlers:
  - source: rails
    except:
      - "Class level methods will no longer inherit scoping from `create!` in"
      - "Uniqueness validator will no longer enforce case sensitive comparison"
      - "app/models/user.rb"
    environments:
      - environment: test
        behavior: raise
      - environment: other
        behavior: log

Ruby Warning Types

Ruby warnings can have an optional category, there are two predefined categories, deprecated and experimental. You can specify a handler to match those categories based on an "only" or "except" matcher. If you want to specially handle warnings that do not have a defined category, you can refer to them as blank.

This handler only handles Ruby warnings that are deprecated, other warnings are ignored.

handlers:
  - environment: all
    ruby_warnings:
      only:
        - deprecated
    behavior: log

This handler handles any Ruby warning with a category

handlers:
  - environment: all
    ruby_warnings:
      except:
        - blank
    behavior: log