From: eregontp@...
Date: 2019-11-27T20:29:42+00:00
Subject: [ruby-core:95999] [Ruby master Feature#16345] Don't emit deprecation warnings by default.

Issue #16345 has been updated by Eregon (Benoit Daloze).


sam.saffron (Sam Saffron) wrote:
> Even with @Eregon's proposed patch running our test suite with warnings is unusable cause of pages of: 

Do you mean @mame's PR from #16289, that is https://github.com/ruby/ruby/pull/2458 ?

Could you try with Jeremy's approach in https://github.com/ruby/ruby/pull/2458#issuecomment-531269374:

```ruby
WARNINGS_SEEN = {}
def Warning.warn(str)
  unless WARNINGS_SEEN[str]
    WARNINGS_SEEN[str] = true
    super
  end
end
```

That approach should filter every duplicate warning.

If it's still too much, I guess a limit of e.g., 100 warnings might be a way to make it more reasonable (and also print warnings are omitted after 100 of them were printed).
A limit of 1 would be very inconvenient to work with when fixing the cause warnings, and not give an idea if an app still has many warnings or not.

----------------------------------------
Feature #16345: Don't emit deprecation warnings by default.
https://bugs.ruby-lang.org/issues/16345#change-82835

* Author: akr (Akira Tanaka)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
We propose that Ruby doesn't emit deprecation warnings by default.

Deprecation warnings are only useful during development for updating Ruby version.
They are not useful during development with current Ruby.
It is especially frustrating when deprecated warnings are generated in gems.
Also, deprecation warnings are totally useless in production environment.

So, we want to emit deprecation warnings only in useful situations.

We propose a command line argument `-W:deprecated` (or `--warning=deprecated`)
and the following methods to enable/disable deprecation warnings.

```ruby
Warning.disable(:deprecated)
Warning.enable(:deprecated)
Warning.enabled?(:deprecated)
```

Currently we don't propose a method to generate a deprecation warning
because currently our main intent is to disable deprecation warnings for 
keyword arguments, and the warnings are generated in C level.

Background:

We talked about keyword arguments during a developer meeting (2019-11-12).
https://bugs.ruby-lang.org/issues/16333
We expect many deprecation warnings to be generated in Ruby 2.7.
They are not useful except for development for Ruby transition, and
they may block transition to Ruby 2.7.

So, we have consensus to disable deprecation warnings by default.
Our design is intentionally minimum because we need this feature for Ruby 2.7.

We chose `Warning.disable(:deprecated)` instead of
re-defining `Warning.warn` in order to avoid string object generation.

Of course, we expect to extend this feature:
Ruby-level deprecation warning generation,
warnings other than deprecation, 
file-based restriction of warning generation, etc.
But this issue doesn't contain them.




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