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Feature #7688

closed

Error hiding with rb_rescue() on Comparable#==, #coerce and others

Added by Eregon (Benoit Daloze) about 11 years ago. Updated almost 7 years ago.

Status:
Closed
Target version:
-
[ruby-core:51389]

Description

Hello,

I believe error hiding is harmful because very dangerous
(it forgets errors which is likely unexpected) and hard to debug.

But I guess the compatibility is the main reason to keep these cases.

In the cases of Comparable#== and #coerce, I believe it is not worth to be compatible with this dangerous behavior
as it will at worse help to discover bugs in #<=> and #coerce methods which would raise an exception.

I doubt anyone rely on this and the #coerce spec (see #7645) itself makes me think this is unexpected behavior.
It would also simplify the spec, and no specific #coerce behavior would be needed to be defined as it would behave as a simple method call without edge cases.

So I think rb_rescue() or rb_rescue2(..., GenericErrorClass, ...) should be avoided if possible.
I analyzed these in the code base and it is used in a couple places:

  • compar.c in cmp_equal(): this is the main offender in this regard with #coerce

  • numeric.c in rb_num_coerce_{cmp,relop}() which call do_coerce(,,FALSE): This is the current subject of #7645.

  • io.c in io_close(): to avoid raising if #close fails, which is likely less problematic,
    although it would be nicer to rescue only IO-related errors and warn when an exception is raised.

  • range.c in range_init(): this is to provide a clearer error. I think it would be nice to show the original error as well.

Removing the general rescue in cmp_equal() revealed a couple bugs in RDoc due to this problem. I guess there are many others in the wild.

Can we please remove this anti-pattern?
I believe impact is only positive and that it should be done as soon as possible.

What do you think?


Related issues 2 (0 open2 closed)

Related to Ruby master - Bug #7940: Mistaken use of inline rescues in stdlibCloseddblack (David Black)02/24/2013Actions
Related to Ruby master - Bug #7645: BigDecimal#== slow when compared to true/falseClosedmrkn (Kenta Murata)01/02/2013Actions
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