Bug #12588
closed
When an exception is re-raised in the "rescue" clause, the back trace does not contain the line in that clause
Description
Given:
$ cat -n foo.rb 1 def foo 2 raise StandardError 3 rescue StandardError => e 4 raise e 5 end 6 7 foo one would reasonably expect to see line 4 to be in the back trace when this file is executed, but one does not.
$ ruby -v foo.rb ruby 2.2.4p230 (2015-12-16 revision 53155) [x86_64-darwin14] foo.rb:2:in `foo': StandardError (StandardError) from foo.rb:7:in `<main>' 
Updated by nobu (Nobuyoshi Nakada) about 9 years ago
I think it's intentional, and don't see why it should contain a new line.
Updated by matz (Yukihiro Matsumoto) about 9 years ago
- Status changed from Open to Rejected
I don't see any "reasonable expectancy". Use-case? Probably you want to use Exception#cause?
Matz.
Updated by hasari (Hiro Asari) about 9 years ago
The current stacktrace is misleading. Without line 4 in it, the implication is that the exception was found on line 2, and was not caught by rescue. In this simple case, the stack trace should contain lines [4,7], not [2,7].
I am not sure how I can use Exception#cause. I tried:
$ cat -n foo.rb 1 def foo 2 raise StandardError 3 rescue StandardError => e 4 puts e.cause.class 5 raise e.cause 6 end 7 8 foo $ ruby -v foo.rb ruby 2.4.0dev (2016-09-21 trunk 56200) [x86_64-darwin15] NilClass foo.rb:5:in `raise': exception object expected (TypeError) from foo.rb:5:in `rescue in foo' from foo.rb:2:in `foo' from foo.rb:8:in `<main>' 
Updated by shyouhei (Shyouhei Urabe) about 9 years ago
Hiro Asari wrote:
I am not sure how I can use
Exception#cause.
Exception#cause makes sense when you raise another exception from inside of a rescue clause. Take a look at this example:
def foo raise 'raised in #foo' end def bar foo rescue raise 'raised in #bar' end def baz bar rescue => e p e # => #<RuntimeError: raised in #bar> p e.cause # => #<RuntimeError: raised in #foo> end baz