[ruby-core:66193] [ruby-trunk - Feature #10042] Deprecate postfix rescue syntax for removal in 3.0

Issue #10042 has been updated by Charles Nutter.


The problem is that postfix rescue is almost always used incorrectly, ending up swallowing 99% of errors that Ruby programs raise. It also masks the very high cost of creating an exception and backtrace (high on MRI, higher on Rubinius, and very high on JRuby/JVM). Finding these bugs (or performance hits) can be very difficult.

I believe the potential for serious bugs outweighs the convenience of this syntax.

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Feature #10042: Deprecate postfix rescue syntax for removal in 3.0
https://bugs.ruby-lang.org/issues/10042#change-49891

* Author: Charles Nutter
* Status: Open
* Priority: Normal
* Assignee: 
* Category: core
* Target version: next minor
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The postfix rescue notation is convenient...but almost always is a really bad antipattern.

An example of the notation:

    Integer(f) rescue f # returns f if it is not parseable as an Integer

It silently ignores all StandardError raised by a piece of code...which often covers *many* more exceptions than the user *wants* to be ignoring.

It also hides the cost of constructing and throwing away all those ignored exceptions.

I believe Matz has even said in the past that he regrets adding the feature.

In any case, I propose that "rescue nil" should be deprecated with a warning (either always on or only when verbose) and we should plan to remove it in 3.0.

Who's with me?!



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