From: duerst@... Date: 2019-09-19T09:11:34+00:00 Subject: [ruby-core:94986] [Ruby master Feature#16153] eventually_frozen flag to gradually phase-in frozen strings Issue #16153 has been updated by duerst (Martin D�rst). `freeze(eventual: false)` gives the impression that it will never be frozen, but the proposal is to have this mean that it is frozen immediately. So it would be better to say `freeze(immediately: true)` for what happens now, and `frozen(immediately: false)` for the new behavior. Please also note the use of the `ly` ending, which makes it more grammatical English (but can be decided on independently). ---------------------------------------- Feature #16153: eventually_frozen flag to gradually phase-in frozen strings https://bugs.ruby-lang.org/issues/16153#change-81606 * Author: Dan0042 (Daniel DeLorme) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- Freezing objects can give us a nice performance boost, but freezing previously non-frozen objects is a backward-incompatible change which is hard to handle because the place where the object is mutated can be far from where it was frozen, and tests might not cover the cases of frozen input vs non-frozen input. I propose adding a flag which gives us a migration path for freezing objects. For purposes of discussion I will call this flag "eventually_frozen". It would act as a pseudo-frozen flag where mutating the object would result in a warning instead of an error. It would also change the return value of `Object#frozen?` so code like `obj = obj.dup if obj.frozen?` would work as expected to remove the warning. Note that eventually_frozen strings cannot be deduplicated, as they are in reality mutable. This way it would be possible for Symbol#to_s (and many others) to return an eventually_frozen string in 2.7 which gives apps and gems time to migrate, before finally becoming a frozen deduplicated string in 3.0. This might even open up a migration path for eventually using `frozen_string_literal:true` as default. For example if it was possible to add `frozen_string_literal:eventual` to all files in a project (or as a global switch), we could run that in production to discover where to fix things, and then change it to `frozen_string_literal:true` for a bug-free performance boost. Proposed changes: * Object#freeze(eventual:false) * if `eventual` keyword is false, set frozen=true and eventually_frozen=false * if `eventual` keyword is true, set eventually_frozen=true UNLESS frozen flag is already true * String#+@ * if eventually_frozen is true, create a duplicate string with eventually_frozen=false * Object#frozen?(eventual:true) * return true if `eventual` keyword and eventually_frozen flag are both true * rb_check_frozen * output warning if eventually_frozen flag is true -- https://bugs.ruby-lang.org/ Unsubscribe: