Issue #15966 has been updated by Eregon (Benoit Daloze).


matz (Yukihiro Matsumoto) wrote:

Thank you for looking at this.

> * Broader audience: I think people who try trunk and previews are big enough for sampling.

I think very few people actually try `trunk` though.
On the other hand, I think many more people reply on the bug tracker and even more so on social media (e.g., Twitter, GitHub).
I believe their opinions matter too.

> I agree to set up the rule to remove half-baked features before the release.

That sounds good, at least it addresses the concern that the feature might not be polished yet and would get in a release because there was not enough time.
Let's establish this rule then.
I think currently it is clear that both features mentioned above feel half-baked.

---

There is another concern that the rule does not address: the frustration by people seeing a feature being added without much discussion.
Basically, I think they feel (at least I do) committers only ask or care about their opinion after the feature is committed, which is of course not ideal.
This might be hard to solve, but I think we need to get better at this.

For instance, I think committing the pipeline operator is not the best way to trigger a productive discussion about it.
I would be very interested to know your opinion on this.

Here are a few ideas on how to collect feedback in a more productive and positive way:
* Opening a Pull Request on GitHub and asking for feedback on the feature. That way, everyone can see it and understand it's not fully decided yet (not yet committed), and they can even try it if they want.
* Asking opinions on Twitter and the bug tracker. This is usually done by discussing on the bug tracker, but for both features mentioned above, I think there was not enough discussion (basically none) before it was committed.
I think asking on Twitter triggers more feedback than the bug tracker, so it is a useful addition, because only a small fraction of the community follows all posts on the bug tracker/the ruby-core mailing list.

I think having a description of the new feature in any of these places would improve the discussion a lot, by being more precise about what the feature is about and what's the reason behind it.

My proposal about experimental flags was a way to try to address this concern, by making it clear the feature is not final and solicits feedback.
Probably it's not the best way to do it, and the 2 ideas I just described seem more straightforward to request feedback.

Sometimes, we might not realize that a feature might trigger a lot of discussion.
I think it's easy to detect though, if we take the care to create a ticket on the issue tracker (or a PR) first and read what people think there.
If there seems to be a lot of disagreement or push back, that sounds like a good time to collect more feedback, *before* committing the feature.
I think syntax changes often need more discussion.

----------------------------------------
Feature #15966: Introducing experimental features behind a flag, disabled by default
https://bugs.ruby-lang.org/issues/15966#change-79923

* Author: Eregon (Benoit Daloze)
* Status: Rejected
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 2.7
----------------------------------------
I feel frustrated with some recent experimental features being added in `trunk`. These features, in my opinion:
* did not have enough discussion before being introduced.
* are going to be almost impossible to remove or even improve.
* got criticisms from hundreds of Rubyists in a couple days, illustrating the feature has major issues.

I think some (or maybe all?) experimental features being added to the language should be disabled by default, and enabled by a flag.
For instance, we could use the features system and have `--enable-experimental=...`.

For instance I'm thinking to 2 experimental features which have many problems reported by many people:
* #4475 / #15723 / #15897 Numbered parameters (`@1`, `@2`, ...)
  I think nobody realized matz would say "yes" after 1 month on https://bugs.ruby-lang.org/issues/4475#note-14, and so there was *zero* discussion about `@1`, `@2` before it was merged, and now we might get stuck with it.
  Many people shared their opinions after, and I think we should consider them carefully, which means not releasing `@1`, `@2` "accidentally" in 2.7.

* #15799 The pipeline operator (`|>`).
  Very little discussion before it was introduced also (the bug was only opened 2 weeks).
  The discussion on the bug tracker seems to have been mostly ignored, the feature was added without a response to concerns on the bug tracker.

Even though both these feature are documented as experimental, if they are released in 2.7, they will not be experimental in any way: there is no warning, nothing special to use it.
So there is no hope to change them if they get in Ruby 2.7.

With the new flag, these experimental features would then be disabled by default, until the core team decides they are stable enough (e.g., there are no major issues with it anymore),
and could still be tried as soon as implemented using e.g., `--enable-experimental=nbargs,pipeline`.

This would allow experimenting with the feature, and discuss about it,
and yet not having the feature set in stone and still be able to change it or remove it.

When such a feature is introduced in Ruby, there is very little chance for it to change or be removed.
In fact, it requires many people in the community to  invest significant time to express the problems of the feature and yet sometimes it's not enough.
If by December, no agreement was reached or no decision by matz was taken, the feature will stay (basically forever) whether it's good or has many issues.
This is not a good process. It requires massive efforts from many people in the community and might result in nothing changed.

By massive efforts from many people, I mean for example:
* Going to Japan in person to discuss with Japanese MRI committers and get a better idea of motivations, thoughts, concerns.
  MRI committers outside Japan and Rubyists in general cannot attend or express their opinion at developer meetings where many decisions are taken, and so have to rely on Japanese MRI committers to relay their opinions.

* Summarizing threads of 100+ comments, and preparing slides or a summary for discussion at a developer meeting (it takes hours).
* Trying to get the motivation for the feature written down on the issue tracker, since often it is not well explained on the issue tracker.
* Writing blog posts sharing thoughts and how to improve the feature/why it should be removed.
* Posting comments on the MRI bug tracker (inconvenient for many people, requires extra account, we see more responses on Twitter or GitHub).
* Writing [blog posts](http://katafrakt.me/2019/06/15/im-worried-about-ruby-future/) or issues like this one to express the general problems of the process for introducing experimental features.

Also, people sometimes respond rather aggressively (me too, I am sorry about that),
because I think people feel it's already too late to share opinions and have an impact on the decision,
the feature might have many problems and yet it's extremely unlikely to change.
I can say it's not a comfortable situation at least, I feel ignored, watching things go wrong and not being able to do much about it.

So I propose `--enable-experimental=...` to make the introduction of experimental features more smooth and allow discussion before the feature is basically written in stone.
What do you think?



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