class Exception

Returns an exception object of the same class as self; useful for creating a similar exception, but with a different message.

With message nil, returns self:

x0 = StandardError.new('Boom') # => #<StandardError: Boom>
x1 = x0.exception              # => #<StandardError: Boom>
x0.__id__ == x1.__id__         # => true

With string-convertible object message (even the same as the original message), returns a new exception object whose class is the same as self, and whose message is the given message:

x1 = x0.exception('Boom') # => #<StandardError: Boom>
x0..equal?(x1)            # => false

# File ext/json/lib/json/add/exception.rb, line 9
def self.json_create(object)
  result = new(object['m'])
  result.set_backtrace object['b']
  result
end

See as_json.

static VALUE
exc_initialize(int argc, VALUE *argv, VALUE exc)
{
    VALUE arg;

    arg = (!rb_check_arity(argc, 0, 1) ? Qnil : argv[0]);
    return exc_init(exc, arg);
}

Returns a new exception object.

The given message should be a string-convertible object; see method message; if not given, the message is the class name of the new instance (which may be the name of a subclass):

Examples:

Exception.new         # => #<Exception: Exception>
LoadError.new         # => #<LoadError: LoadError> # Subclass of Exception.
Exception.new('Boom') # => #<Exception: Boom>

static VALUE
exc_s_to_tty_p(VALUE self)
{
    return RBOOL(rb_stderr_tty_p());
}

Returns true if exception messages will be sent to a terminal device.

static VALUE
exc_equal(VALUE exc, VALUE obj)
{
    VALUE mesg, backtrace;

    if (exc == obj) return Qtrue;

    if (rb_obj_class(exc) != rb_obj_class(obj)) {
        int state;

        obj = rb_protect(try_convert_to_exception, obj, &state);
        if (state || UNDEF_P(obj)) {
            rb_set_errinfo(Qnil);
            return Qfalse;
        }
        if (rb_obj_class(exc) != rb_obj_class(obj)) return Qfalse;
        mesg = rb_check_funcall(obj, id_message, 0, 0);
        if (UNDEF_P(mesg)) return Qfalse;
        backtrace = rb_check_funcall(obj, id_backtrace, 0, 0);
        if (UNDEF_P(backtrace)) return Qfalse;
    }
    else {
        mesg = rb_attr_get(obj, id_mesg);
        backtrace = exc_backtrace(obj);
    }

    if (!rb_equal(rb_attr_get(exc, id_mesg), mesg))
        return Qfalse;
    return rb_equal(exc_backtrace(exc), backtrace);
}

Returns whether object is the same class as self and its message and backtrace are equal to those of self.

# File ext/json/lib/json/add/exception.rb, line 29
def as_json(*)
  {
    JSON.create_id => self.class.name,
    'm'            => message,
    'b'            => backtrace,
  }
end

Methods Exception#as_json and Exception.json_create may be used to serialize and deserialize a Exception object; see Marshal.

Method Exception#as_json serializes self, returning a 2-element hash representing self:

require 'json/add/exception'
x = Exception.new('Foo').as_json # => {"json_class"=>"Exception", "m"=>"Foo", "b"=>nil}

Method JSON.create deserializes such a hash, returning a Exception object:

Exception.json_create(x) # => #<Exception: Foo>

static VALUE
exc_backtrace(VALUE exc)
{
    VALUE obj;

    obj = rb_attr_get(exc, id_bt);

    if (rb_backtrace_p(obj)) {
        obj = rb_backtrace_to_str_ary(obj);
        /* rb_ivar_set(exc, id_bt, obj); */
    }

    return obj;
}

Returns a backtrace value for self; the returned value depends on the form of the stored backtrace value:

• Array of Thread::Backtrace::Location objects: returns the array of strings given by Exception#backtrace_locations.map {|loc| loc.to_s }. This is the normal case, where the backtrace value was stored by Kernel#raise.

• Array of strings: returns that array. This is the unusual case, where the backtrace value was explicitly stored as an array of strings.

• nil: returns nil.

Example:

begin
  1 / 0
rescue => x
  x.backtrace.take(2)
end
# => ["(irb):132:in `/'", "(irb):132:in `<top (required)>'"]

see Backtraces.

static VALUE
exc_backtrace_locations(VALUE exc)
{
    VALUE obj;

    obj = rb_attr_get(exc, id_bt_locations);
    if (!NIL_P(obj)) {
        obj = rb_backtrace_to_location_ary(obj);
    }
    return obj;
}

Returns a backtrace value for self; the returned value depends on the form of the stored backtrace value:

• Array of Thread::Backtrace::Location objects: returns that array.

• Array of strings or nil: returns nil.

Example:

begin
  1 / 0
rescue => x
  x.backtrace_locations.take(2)
end
# => ["(irb):150:in `/'", "(irb):150:in `<top (required)>'"]

See Backtraces.

static VALUE
exc_cause(VALUE exc)
{
    return rb_attr_get(exc, id_cause);
}

Returns the previous value of global variable $!, which may be nil (see Global Variables):

begin
  raise('Boom 0')
rescue => x0
  puts "Exception: #{x0};  $!: #{$!};  cause: #{x0.cause.inspect}."
  begin
    raise('Boom 1')
  rescue => x1
    puts "Exception: #{x1};  $!: #{$!};  cause: #{x1.cause}."
    begin
      raise('Boom 2')
    rescue => x2
      puts "Exception: #{x2};  $!: #{$!};  cause: #{x2.cause}."
    end
  end
end

Output:

Exception: Boom 0;  $!: Boom 0;  cause: nil.
Exception: Boom 1;  $!: Boom 1;  cause: Boom 0.
Exception: Boom 2;  $!: Boom 2;  cause: Boom 1.

static VALUE
exc_detailed_message(int argc, VALUE *argv, VALUE exc)
{
    VALUE opt;

    rb_scan_args(argc, argv, "0:", &opt);

    VALUE highlight = check_highlight_keyword(opt, 0);

    extern VALUE rb_decorate_message(const VALUE eclass, VALUE emesg, int highlight);

    return rb_decorate_message(CLASS_OF(exc), rb_get_message(exc), RTEST(highlight));
}

Returns the message string with enhancements:

• Includes the exception class name in the first line.

• If the value of keyword highlight is true, includes bolding and underlining ANSI codes (see below) to enhance the appearance of the message.

Examples:

begin
  1 / 0
rescue => x
  p x.message
  p x.detailed_message                  # Class name added.
  p x.detailed_message(highlight: true) # Class name, bolding, and underlining added.
end

Output:

"divided by 0"
"divided by 0 (ZeroDivisionError)"
"\e[1mdivided by 0 (\e[1;4mZeroDivisionError\e[m\e[1m)\e[m"

This method is overridden by some gems in the Ruby standard library to add information:

• DidYouMean::Correctable#detailed_message.

• ErrorHighlight::CoreExt#detailed_message.

• SyntaxSuggest#detailed_message.

An overriding method must be tolerant of passed keyword arguments, which may include (but may not be limited to):

• :highlight.

• :did_you_mean.

• :error_highlight.

• :syntax_suggest.

An overriding method should also be careful with ANSI code enhancements; see Messages.

static VALUE
exc_exception(int argc, VALUE *argv, VALUE self)
{
    VALUE exc;

    argc = rb_check_arity(argc, 0, 1);
    if (argc == 0) return self;
    if (argc == 1 && self == argv[0]) return self;
    exc = rb_obj_clone(self);
    rb_ivar_set(exc, id_mesg, argv[0]);
    return exc;
}

Returns an exception object of the same class as self; useful for creating a similar exception, but with a different message.

With message nil, returns self:

x0 = StandardError.new('Boom') # => #<StandardError: Boom>
x1 = x0.exception              # => #<StandardError: Boom>
x0.__id__ == x1.__id__         # => true

With string-convertible object message (even the same as the original message), returns a new exception object whose class is the same as self, and whose message is the given message:

x1 = x0.exception('Boom') # => #<StandardError: Boom>
x0..equal?(x1)            # => false

static VALUE
exc_full_message(int argc, VALUE *argv, VALUE exc)
{
    VALUE opt, str, emesg, errat;
    VALUE highlight, order;

    rb_scan_args(argc, argv, "0:", &opt);

    highlight = check_highlight_keyword(opt, 1);
    order = check_order_keyword(opt);

    {
        if (NIL_P(opt)) opt = rb_hash_new();
        rb_hash_aset(opt, sym_highlight, highlight);
    }

    str = rb_str_new2("");
    errat = rb_get_backtrace(exc);
    emesg = rb_get_detailed_message(exc, opt);

    rb_error_write(exc, emesg, errat, str, opt, highlight, order);
    return str;
}

Returns an enhanced message string:

• Includes the exception class name.

• If the value of keyword highlight is true (not nil or false), includes bolding ANSI codes (see below) to enhance the appearance of the message.

• Includes the backtrace:

  • If the value of keyword order is :top (the default), lists the error message and the innermost backtrace entry first.

  • If the value of keyword order is :bottom, lists the error message the the innermost entry last.

Example:

def baz
  begin
    1 / 0
  rescue => x
    pp x.message
    pp x.full_message(highlight: false).split("\n")
    pp x.full_message.split("\n")
  end
end
def bar; baz; end
def foo; bar; end
foo

Output:

"divided by 0"
["t.rb:3:in `/': divided by 0 (ZeroDivisionError)",
 "\tfrom t.rb:3:in `baz'",
 "\tfrom t.rb:10:in `bar'",
 "\tfrom t.rb:11:in `foo'",
 "\tfrom t.rb:12:in `<main>'"]
["t.rb:3:in `/': \e[1mdivided by 0 (\e[1;4mZeroDivisionError\e[m\e[1m)\e[m",
 "\tfrom t.rb:3:in `baz'",
 "\tfrom t.rb:10:in `bar'",
 "\tfrom t.rb:11:in `foo'",
 "\tfrom t.rb:12:in `<main>'"]

An overriding method should be careful with ANSI code enhancements; see Messages.

static VALUE
exc_inspect(VALUE exc)
{
    VALUE str, klass;

    klass = CLASS_OF(exc);
    exc = rb_obj_as_string(exc);
    if (RSTRING_LEN(exc) == 0) {
        return rb_class_name(klass);
    }

    str = rb_str_buf_new2("#<");
    klass = rb_class_name(klass);
    rb_str_buf_append(str, klass);

    if (RTEST(rb_str_include(exc, rb_str_new2("\n")))) {
        rb_str_catf(str, ":%+"PRIsVALUE, exc);
    }
    else {
        rb_str_buf_cat(str, ": ", 2);
        rb_str_buf_append(str, exc);
    }

    rb_str_buf_cat(str, ">", 1);

    return str;
}

Returns a string representation of self:

x = RuntimeError.new('Boom')
x.inspect # => "#<RuntimeError: Boom>"
x = RuntimeError.new
x.inspect # => "#<RuntimeError: RuntimeError>"

static VALUE
exc_message(VALUE exc)
{
    return rb_funcallv(exc, idTo_s, 0, 0);
}

Returns to_s.

See Messages.

static VALUE
exc_set_backtrace(VALUE exc, VALUE bt)
{
    VALUE btobj = rb_location_ary_to_backtrace(bt);
    if (RTEST(btobj)) {
        rb_ivar_set(exc, id_bt, btobj);
        rb_ivar_set(exc, id_bt_locations, btobj);
        return bt;
    }
    else {
        return rb_ivar_set(exc, id_bt, rb_check_backtrace(bt));
    }
}

Sets the backtrace value for self; returns the given +value:

x = RuntimeError.new('Boom')
x.set_backtrace(%w[foo bar baz]) # => ["foo", "bar", "baz"]
x.backtrace                      # => ["foo", "bar", "baz"]

The given value must be an array of strings, a single string, or nil.

Does not affect the value returned by backtrace_locations.

See Backtraces.

# File ext/json/lib/json/add/exception.rb, line 46
def to_json(*args)
  as_json.to_json(*args)
end

Returns a JSON string representing self:

require 'json/add/exception'
puts Exception.new('Foo').to_json

Output:

{"json_class":"Exception","m":"Foo","b":null}

static VALUE
exc_to_s(VALUE exc)
{
    VALUE mesg = rb_attr_get(exc, idMesg);

    if (NIL_P(mesg)) return rb_class_name(CLASS_OF(exc));
    return rb_String(mesg);
}

Returns a string representation of self:

x = RuntimeError.new('Boom')
x.to_s # => "Boom"
x = RuntimeError.new
x.to_s # => "RuntimeError"