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MRI's rb_f_readline calls ARGF.readline (argf_readline directly when the receiver is ARGF, otherwise forward). Kernel#readline called Kernel#gets and raised EOFError on nil, so a non-IO $stdin had its lines counted in ARGF.lineno and ARGF.readline overrides were ignored. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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October 16, 2026 02:05
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Follow-up to #9785, as discussed there (headius: "I support both the Kernel.readline => ARGF move and the deprecation cleanups").
MRI's
rb_f_readlinecallsARGF.readline(argf_readlinedirectly when the receiver is ARGF, otherwiseforward). JRuby'sKernel#readlinecalledKernel#getsand raised EOFError onnil. That differs from MRI in two observable ways, both measured in this comment:jruby-10.0$stdin:readline; readline; [$., ARGF.lineno][0, 0][2, 2][0, 0]def ARGF.readline(*) = "patched\n"; readline"patched\n""a\n""patched\n"def ARGF.gets(*) = "patched\n"; readline"a\n""patched\n""a\n"The last row is the compatibility risk: code that stubs
ARGF.getsto feed a top-levelreadlinestops working, and code that stubsARGF.readlinestarts working. That is the CRuby behavior.Changes
RubyKernel.readlinemirrorsKernel#gets:RubyArgsFile.readlinewhenrecvis ARGF, otherwise a forwardedreadlinecall.KernelSitesgets areadlinecall site next togets.Kernel#readline calls ARGF.readline(fails onjruby-10.0with the mock never receivingreadline, passes here).Testing
mspec ciovercore/{kernel,argf,io}: 4503 examples, 2 failures. Those are the same twoKernel#require ... c-extension file exists but loading failsfailures as unmodifiedjruby-10.0.🤖 Generated with Claude Code