From: matz@... Date: 2019-02-07T07:08:52+00:00 Subject: [ruby-core:91457] [Ruby trunk Feature#15567] Allow ensure to match specific situations Issue #15567 has been updated by matz (Yukihiro Matsumoto). Status changed from Open to Rejected The language feature similar to `ensure` can be observed in many languages (`unwind-protocol` in Lisp, `defer` in Go, `finally` in Java and others), but neither of them considers the situation. That indicates there's no real-world use-case for it. So currently I believe there's no benefit enough the implementation cost and making the language more complex. Matz. ---------------------------------------- Feature #15567: Allow ensure to match specific situations https://bugs.ruby-lang.org/issues/15567#change-76717 * Author: ioquatix (Samuel Williams) * Status: Rejected * Priority: Normal * Assignee: ioquatix (Samuel Williams) * Target version: ---------------------------------------- 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: