Module: Xqsr3::Diagnostics::Exceptions::WithCause

Defined in:
lib/xqsr3/diagnostics/exceptions/with_cause.rb

Overview

This inclusion module adds to an exception class the means to chain a cause (aka inner-exception), which is then exposed with the cause attribute.

Examples:

Passing an exception cause as a parameter

class ConfigurationError < StandardError
  include Xqsr3::Diagnostics::Exceptions::WithCause
end

cause = ArgumentError.new 'port is not numeric'
error = ConfigurationError.new cause

error.cause # => cause
error.chained_message # => 'port is not numeric'

Constant Summary collapse

INSPECT_HIDDEN_FIELDS =

Array of hidden fields.

[ 'has_implicit_message', 'uses_cause_message' ]

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#cause ⇒ Object (readonly)

The cause / inner-exception, if any, specified to the instance initialiser. This attribute shadows Exception#cause (the interpreter's raise-chain cause); for includers, #cause refers to this module's @cause.



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# File 'lib/xqsr3/diagnostics/exceptions/with_cause.rb', line 147

def cause
  @cause
end

#options ⇒ Object (readonly)

The options passed to the initialiser, with :cause removed, if present.



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# File 'lib/xqsr3/diagnostics/exceptions/with_cause.rb', line 151

def options
  @options
end

Instance Method Details

#chained_backtrace ⇒ Object

A combination of the backtrace(s) of all chained exception(s).



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# File 'lib/xqsr3/diagnostics/exceptions/with_cause.rb', line 198

def chained_backtrace

  b = backtrace

  return b unless cause

  cb = cause.respond_to?(:chained_backtrace) ? cause.chained_backtrace : cause.backtrace

  (cb - b) + b
end

#chained_message(**options) ⇒ Object

Message obtained by concatenation of all chained exceptions' messages.

Signature

  • Parameters:

    • options (+Hash+) Options that control the behaviour of the method;

  • Options:

    • :separator (+String+) A string used to separate each chained exception message. Defaults to ": ";


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# File 'lib/xqsr3/diagnostics/exceptions/with_cause.rb', line 162

def chained_message **options

  return message unless cause
  return message if @uses_cause_message

  m = message
  c = cause
  cm = c.respond_to?(:chained_message) ? c.chained_message(**options) : c.message

  return m if (cm || '').empty?
  return cm if (m || '').empty?

  sep = options[:separator] || ': '

  "#{m}#{sep}#{cm}"
end

#chainees ⇒ Object

An array of exceptions in the chain, excluding self.



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# File 'lib/xqsr3/diagnostics/exceptions/with_cause.rb', line 180

def chainees

  return [] unless cause

  r = [ cause ]

  r += cause.chainees if cause.respond_to? :chainees

  r
end

#exceptions ⇒ Object

An array of exceptions in the chain, including self.



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# File 'lib/xqsr3/diagnostics/exceptions/with_cause.rb', line 192

def exceptions

  [ self ] + chainees
end

#initialize(*args, **options) ⇒ Object

Defines an initializer for an exception class that allows a cause (aka an inner exception) to be specified, either as the first or last argument or as a :cause option.

Signature

  • Parameters:

    • args 0+ arguments passed through to the +include+-ing class' initialiser;
    • options (+Hash+) Options that control the behaviour of the method;

  • Options:

    • :cause - The exception to be used as a cause, and ensures that that is not inferred from the arguments. May be nil to ensure that no cause is inferred;


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# File 'lib/xqsr3/diagnostics/exceptions/with_cause.rb', line 90

def initialize(*args, **options)

  @uses_cause_message = false

  cz = options[:cause]

  if cz

    options = options.reject { |k, v| k == :cause }

    @has_implicit_message = args.empty?

    super(*args)

    warn 'unexpected implicit message' if @has_implicit_message && self.message != self.class.to_s

    @cause = cz
  else

    cz_ix = args.index { |arg| ::Exception === arg }

    if cz_ix

      args = args.dup

      cz = args.delete_at cz_ix

      if args.empty?

        if !(cz.message || '').empty? && cz.class.to_s != cz.message

          @uses_cause_message = true

          args = [ cz.message ]
        end
      end
    else

      cz = $!
    end

    @has_implicit_message = args.empty?

    super(*args)

    warn 'unexpected implicit message' if @has_implicit_message && self.message != self.class.to_s

    @cause = cz
  end

  @options = options
end