Feature #17259: Kernel#warn should ignore <internal: entries

• Status: Closed
• Assignee: -
• Target version: 3.0

[Eregon (Benoit Daloze)]

Kernel#warn currently does not skip <internal: entries from core library methods defined in Ruby.
This can cause rather unhelpful locations to be used for warnings.

For instance:

$ ruby -v --disable=gems -e 'def deprecated; warn "use X instead", uplevel: 1; end; tap(&:deprecated)'
ruby 3.0.0preview1 (2020-09-25 master 0096d2b895) [x86_64-linux]
<internal:kernel>:90: warning: use X instead
# expected: "-e:1: warning: use X instead"

Note that RubyGems overrides Kernel#warn since https://github.com/rubygems/rubygems/pull/2442 and https://github.com/rubygems/rubygems/blob/c1bafab1d84e0aad06e377e9db4b74cccab4b43a/lib/rubygems/core_ext/kernel_warn.rb#L42,
so --disable-gems is needed to observe this behavior.
I think it is very suboptimal that RubyGems needs to monkey-patch Kernel#warn to remove RubyGems' require from Kernel#warn location.
That is both fragile (as we've seen from various incompatible behavior and bugs in that monkey-patch) and inefficient (walking the stack multiple times).

So I would suggest to actually skip all backtraces entries starting with <internal: for Kernel#warn(message, uplevel:).
BTW this is already what TruffleRuby does.

As a bonus, by filtering out <internal:, RubyGems could define its require in an eval(code, nil, '<internal:rubygems-require>', line) and it would automatically be skipped, without needing to monkey-patch Kernel#warn at all!

[Eregon (Benoit Daloze)]

• Description updated (diff)

[jeremyevans0 (Jeremy Evans)]

I agree with removing the Rubygems override of Kernel#warn (the only Kernel method Rubygems should override is require). Skipping <internal: entries for uplevel makes sense to me.

[nobu (Nobuyoshi Nakada)]

Essentially uplevel: option is useless in some cases.
For instance, it cannot work to skip frames in the same file or directory.

[Eregon (Benoit Daloze)]

nobu (Nobuyoshi Nakada) wrote in #note-3:

Essentially uplevel: option is useless in some cases.
For instance, it cannot work to skip frames in the same file or directory.

Yes, some libraries might want to emit warnings and ignore their own my_gem/lib/.
That however would need to make warn somehow take some extra context, because only warnings of that library should ignore my_gem/lib/, other calls to warn should not.
Maybe warn(message, uplevel: n, ignore: [path1, path2]).
That would not work for RubyGems' require, where warning are not emitted by RubyGems but by anything else.

In practice, I think gems should be able to know if they call themselves directly or not, so there should be no need to skip my_gem/lib/.
I might be wrong about that.

OTOH for core library methods and RubyGems' require, it seems clear it would never be useful to show their location for warn(uplevel:).
So I think ignoring <internal: is a useful step on its own, and such entries should be ignored by default.

It also keeps compatibility with older Rubies which had less core methods defined in Ruby, which should be a transparent implementation detail, at least for warn(uplevel:).

[nobu (Nobuyoshi Nakada)]

• Tracker changed from Bug to Feature
• ruby -v deleted (ruby 3.0.0preview1 (2020-09-25 master 0096d2b895) [x86_64-linux])
• Backport deleted (2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN)

[Eregon (Benoit Daloze)]

PR: https://github.com/ruby/ruby/pull/3647

[matz (Yukihiro Matsumoto)]

Accepted.

Matz.

[Eregon (Benoit Daloze)]

• Status changed from Open to Closed

Applied in changeset git|cffdacb15a363321e1c1879aa7d94924acafd1cf.

---

Ignore <internal: entries from core library methods for Kernel#warn(message, uplevel: n)

• Fixes [Bug #17259]

[Eregon (Benoit Daloze)]

PR to RubyGems so RubyGems won't need to override Kernel#warn anymore: https://github.com/rubygems/rubygems/pull/4075