Feature #19752: Allow `--backtrace-limit` to appear in RUBYOPT

• Status: Closed
• Assignee: matz (Yukihiro Matsumoto)
• Target version: -

[tomstuart (Tom Stuart)]

The --backtrace-limit option was added in #8661 but it is not currently supported in the RUBYOPT environment variable, which appears to be a mistake. Unlike other long options which are not allowed in RUBYOPT (e.g. --copyright, --version, --dump and --help) it does not cause the interpreter to terminate, and cannot cause harm if read from the environment. During the initial discussion about the --backtrace-limit feature, Matz suggested that he expected RUBYOPT to allow this option.

Patch here, which also documents --backtrace-limit on Ruby’s man page: https://github.com/ruby/ruby/pull/8010

[mame (Yusuke Endoh)]

• Status changed from Open to Assigned
• Assignee set to matz (Yukihiro Matsumoto)

The proposed patch includes a change to treat it as unspecified with -1. I would like to get Matz's approval on this.

[tomstuart (Tom Stuart)]

My main goal is to allow RUBYOPT to support --backtrace-limit.

I am happy to remove the ability to say --backtrace-limit=-1 from my patch if it’s undesirable, but since -1 is already a meaningful value for the backtrace limit, it seems useful and unsurprising to allow it. For example, this makes it possible to use RUBYOPT to restore the default backtrace limit by saying RUBYOPT="--backtrace-limit=-1" ruby --backtrace-limit=5.

[matz (Yukihiro Matsumoto)]

Basically accepted, including --backtrace-limit=-1. But as far as I understand, command line options are (and should be) higher precedence than RUBYOPT.

Matz.

[tomstuart (Tom Stuart)]

Thank you for accepting!

Currently (i.e. on master with this patch applied), --backtrace-limit in RUBYOPT has higher precedence than the command line option:

% ruby -v
ruby 3.3.0dev (2023-07-13T07:54:27Z backtrace-limit-fi.. b1b0395cd1) [arm64-darwin22]
last_commit=Add `--backtrace-limit` option to the man page

% RUBYOPT="--backtrace-limit=10" ruby --backtrace-limit=5 -e "puts Thread::Backtrace.limit"
10

Is this a bug?

[matz (Yukihiro Matsumoto)]

Yes, it should be fixed. I think @nobu (Nobuyoshi Nakada) is working on it.

Matz.

[nobu (Nobuyoshi Nakada)]

https://github.com/ruby/ruby/pull/8068

Also you'll need the tests.

    env = {"RUBYOPT" => "--backtrace-limit=5"}
    assert_in_out_err([env], "p Thread::Backtrace.limit", ['5'], [])
    assert_in_out_err([env, "--backtrace-limit=1"], "p Thread::Backtrace.limit", ['1'], [])

[tomstuart (Tom Stuart)]

Thank you @nobu (Nobuyoshi Nakada). I’ve rebased https://github.com/ruby/ruby/pull/8010 onto master to include your fix, and added your test.

[nobu (Nobuyoshi Nakada)]

• Status changed from Assigned to Closed