From: samuel@... Date: 2021-06-01T23:15:34+00:00 Subject: [ruby-core:104131] [Ruby master Feature#15567] Allow ensure to match specific situations Issue #15567 has been updated by ioquatix (Samuel Williams). I suspect that there is existing buggy code which has ensure blocks and checks `$!` which fails in the case I mentioned. I think the ensure block should be able to capture the current exception without using a global. I like the proposed syntax: ``` begin ... ensure => exception if exception abort else commit end end ``` It allows existing code that uses `if $!` to be retrofitted to do the correct thing. ---------------------------------------- Feature #15567: Allow ensure to match specific situations https://bugs.ruby-lang.org/issues/15567#change-92303 * Author: ioquatix (Samuel Williams) * Status: Rejected * Priority: Normal * Assignee: ioquatix (Samuel Williams) ---------------------------------------- There are some situations where `rescue Exception` or `ensure` are not sufficient to correctly, efficiently and easily handle abnormal flow control. Take the following program for example: ``` def doot yield ensure # Did the function run to completion? return "abnormal" if $! end puts doot{throw :foo} puts doot{raise "Boom"} puts doot{"Hello World"} catch(:foo) do puts doot{throw :foo} end ``` Using `rescue Exception` is not sufficient as it is not invoked by `throw`. Using `ensure` is inefficient because it's triggered every time, even though exceptional case might never happen or happen very infrequently. I propose some way to limit the scope of the ensure block: ``` def doot yield ensure when raise, throw return "abnormal" end ``` The scope should be one (or more) of `raise`, `throw`, `return`, `next`, `break`, `redo`, `retry` (everything in `enum ruby_tag_type` except all except for `RUBY_TAG_FATAL`). Additionally, it might be nice to support the inverted pattern, i.e. ``` def doot yield ensure when not return return "abnormal" end ``` Inverted patterns allow user to specify the behaviour without having problems if future scopes are introduced. `return` in this case matches both explicit and implicit. -- https://bugs.ruby-lang.org/ Unsubscribe: