From: samuel@... Date: 2021-06-04T04:22:37+00:00 Subject: [ruby-core:104160] [Ruby master Feature#15567] Allow ensure to match specific situations Issue #15567 has been updated by ioquatix (Samuel Williams). Here are some examples of situations where `$!` is used inside `ensure` block. In every case, there is a potential buggy behaviour. https://github.com/drbrain/net-http-persistent/blob/75574f2546a08aa2663b06a2e005bcf2ee304f13/lib/net/http/persistent.rb#L230 https://github.com/copiousfreetime/launchy/blob/80e723ebf2d9e73d35ae5de31a73268eb6c46ecc/lib/launchy.rb#L36-L40 https://github.com/rails/spring/blob/577cf01f232bb6dbd0ade7df2df2ac209697e741/lib/spring/application.rb#L296-L301 https://github.com/ahoward/open4/blob/2bc378285dcec9c88613fd4def57a58606c0680b/lib/open4.rb#L189-L192 I can find more, but I think it's sufficient to show the problem. ---------------------------------------- Feature #15567: Allow ensure to match specific situations https://bugs.ruby-lang.org/issues/15567#change-92335 * Author: ioquatix (Samuel Williams) * Status: Open * 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: