Bug #20700: `warn_cr_in_shebang()` doesn't fire if there's no `\n`

• Status: Feedback
• Assignee: -
• Target version: -
• ruby -v: ruby 3.3.4 (2024-07-09 revision be1089c8ec) [arm64-darwin23]
• Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN

[AMomchilov (Alexander Momchilov)]

The warn_cr_in_shebang() function looks for \r\n together, but the \r should emit a warning, regardless if there's also a \n or not.

#!/usr/bin/ruby

require "tempfile"
require "open3"

def run_rb(ruby_src)
  puts "===== Output of #{ruby_src.inspect}:"
  Tempfile.create("script.rb") do |f|
    f.print(ruby_src)
    f.close
    
    stdout_and_stderr_str, status = Open3.capture2e("/opt/rubies/3.3.4/bin/ruby", f.path)
    raise unless status.success?
    puts stdout_and_stderr_str
  end
end

run_rb("#!ruby")     # ✅ no warning
run_rb("#!ruby\r")   # ❌ no warning!
run_rb("#!ruby\r\n") # ✅ warns
run_rb("#!ruby -Eutf-8\r\n123") # ✅ warns

[nobu (Nobuyoshi Nakada)]

If there is not a \n, that file has only a comment.
It would be another thing than \r\n, I think.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Feedback

First of all, not all operating systems consider a line that doesn't end with a newline to be a shebang.

For example, a file with "#!/x\n" fails as "cannot execute: required file not found" both on Linux and macOS.
However, a file with "#!/x", no newline, just runs silently on macOS while fails on Linux as well as the above.

In addition, prism does not consider a line like macOS.

$ echo -ne $'#!ruby -Ex' | ruby -wc
ruby: unknown encoding name - x (RuntimeError)
bash: exit 1

$ echo -ne $'#!ruby -Ex' | ruby -wc --parser=prism
Syntax OK