Issue #8661 has been updated by kou (Kouhei Sutou).


I like this change. It's unbelievable.

I thought that I don't like this feature because I was confused Python's backtrace behavior (most recent call last).

I used trunk in a few weeks but I was not confused the current behavior. Instead it was convenient.

I noticed that I confirm error message and then backtrace on error. It was convenient that error message is shown at the last. I could confirm backtrace from the bottom to the top naturally.

Python's backtrace behavior doesn't show index:

```python
def a():
    x()

def b():
    a()

b()
```

```console
% python /tmp/a.py
Traceback (most recent call last):
  File "/tmp/a.py", line 7, in <module>
    b()
  File "/tmp/a.py", line 5, in b
    a()
  File "/tmp/a.py", line 2, in a
    x()
NameError: global name 'x' is not defined
```

Ruby 2.5's one shows index:

```ruby
def a
  x
end

def b
  a
end

b
```

```console
% ruby /tmp/a.rb
Traceback (most recent call last):
	2: from /tmp/a.rb:9:in `<main>'
	1: from /tmp/a.rb:6:in `b'
/tmp/a.rb:2:in `a': undefined local variable or method `x' for main:Object (NameError)
```

It may be helpful to recognize backtrace order.


I've added the same behavior to test-unit and released a new version.


----------------------------------------
Feature #8661: Add option to print backstrace in reverse order(stack frames first & error last)
https://bugs.ruby-lang.org/issues/8661#change-68267

* Author: gary4gar (Gaurish Sharma)
* Status: Closed
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 
----------------------------------------
Currently the way ruby prints the backtrace is that the error comes first & then the stack frames. like this

```
  Main Error Message
stack frame 1
stack frame 2
stack frame 3
.....
```

 this is perfectly fine provided

1. Backstraces are short, so fits in terminal.hence, no need to scroll.
2. you read it from top to bottom.


But, I am a rails developer where 

1. Backstraces are always HUGE, therefore seldom don't fit in terminal. Means LOTS of scrolling to do everytime we get an error.
2. in terminal we tend to read backstraces from bottom to top, especially when tailing(tail -f) the production logs. 
3. people, who practice Test-driven development literally spend most of their time scrolling to read backstraces to the point most end up buying a larger display.

Proposed Solution:
 Please add a way so we can configure backstraces to be printed in reverse order. so if you are reading from bottom, say from terminal, you can get the main error message without need to scroll. like this


```
stack frame 3
stack frame 2
stack frame 1
 Main Error Message
..... 
```

this would save lot of time because when the error message is print at the bottom, no need to scroll for reading it. Not sure if this can be done today. I tried Overriding Exception#backtrace but it caused stack level too deep & illegal hardware instruction Error.

Attached are currently what backstrace currently looks like & how there be an option to make it look for comparison.

---Files--------------------------------
current.log (5.13 KB)
proposed.log (4.9 KB)


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