[ruby-core:91247] [Ruby trunk Feature#5653] "I strongly discourage the use of autoload in any standard libraries" (Re: autoload will be dead)

Issue #5653 has been updated by fxn (Xavier Noria).


Let me add a couple of things.

In case const_missing is discussed, these are the reasons why implementing autoloading based on const_missing doesn't fly (from memory):

1) The nesting is unknown.
2) Whether the missing constant was relative is unknown.
3) Since const_missing is the last resort in the constant resolution algorithms, you may miss an autoload if some class/module up in the nesting or the ancestor chain happens to have a constant with the same name.
4) It is not thread-safe.

On the other hand, Zeitwerk is based on these techniques (some are not portable as of this writing, but would hope they are in the future for compatibility with CRuby):

1) Kernel#autoload, related API, and the fact that it is thread-safe.
2) Constants API.
3) Kernel#autoload calls Kernel#require (Zeitwerk decorates it).
4) TracePoint for the :class event if there is at least one explicit namespace (hotel.rb & hotel/pricing.rb), to support the very common edge case in which Hotel includes Hotel::Pricing and you need to set an autoload on Hotel for :Pricing before that line is reached. (I am aware of https://bugs.ruby-lang.org/issues/14104 and this week I have made some changes in that line, as in https://github.com/fxn/zeitwerk/commit/a1bd83b10521f41f7f74e921602839a1813d11e4).

Additionally, Zeitwerk by design uses internally absolute paths only, there are no lookups in $LOAD_PATH or autoload paths, gems using Zeitwerk should load a tad faster. Even more, a code base managed by Zeitwerk does not even need to be in $LOAD_PATH.

Any other information that you'd like to know please just tell me!





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Feature #5653: "I strongly discourage the use of autoload in any standard libraries" (Re: autoload will be dead)
https://bugs.ruby-lang.org/issues/5653#change-76493

* Author: matz (Yukihiro Matsumoto)
* Status: Assigned
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: Next Major
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Hi,
 
Today, I talked with NaHi about enhancing const_missing to enable
autoload-like feature with nested modules.  But autoload itself has
fundamental flaw under multi-thread environment.  I should have remove
autoload when I added threads to the language (threads came a few
months after autoload).
 
So I hereby declare the future deprecation of autoload.  Ruby will
keep autoload for a while, since 2.0 should keep compatibility to 1.9.
But you don't expect it will survive further future, e.g. 3.0.
 
I strongly discourage the use of autoload in any standard libraries.
 
matz.

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noname (500 Bytes)
5653.pdf (38.3 KB)


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