If the environment variable LANG is empty, the debugger command will error

[naitoh]

Your environment

• ruby -v:

ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [arm64-darwin24]

• rdbg -v:

rdbg 1.10.0

Describe the bug

If the environment variable LANG is empty, the debugger command will error.

To Reproduce

$ LANG= ruby -e 'puts Encoding.default_external' 
US-ASCII
$ LANG= ruby -e 'require "debug"; debugger' 
# No sourcefile available for -e
=>#0	<main> at -e:1
#<Thread:0x0000000105e9c040@DEBUGGER__::SESSION@server /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:179 run> terminated with exception (report_on_exception is true):
/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:207:in 'String#strip!': invalid byte sequence in US-ASCII (Encoding::CompatibilityError)
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:207:in 'block in DEBUGGER__::Console#load_history'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:206:in 'Array#each'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:206:in 'DEBUGGER__::Console#load_history'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:183:in 'DEBUGGER__::Console#load_history_if_not_loaded'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:25:in 'DEBUGGER__::Console#readline_setup'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:100:in 'DEBUGGER__::Console#readline'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:78:in 'block in DEBUGGER__::UI_LocalConsole#readline'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:90:in 'block in DEBUGGER__::UI_LocalConsole#setup_interrupt'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:1989:in 'DEBUGGER__::Session#intercept_trap_sigint'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:83:in 'DEBUGGER__::UI_LocalConsole#setup_interrupt'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:77:in 'DEBUGGER__::UI_LocalConsole#readline'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:445:in 'DEBUGGER__::Session#wait_command'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:405:in 'block in DEBUGGER__::Session#wait_command_loop'
	from <internal:kernel>:168:in 'Kernel#loop'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:404:in 'DEBUGGER__::Session#wait_command_loop'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:330:in 'DEBUGGER__::Session#process_event'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:255:in 'DEBUGGER__::Session#session_server_main'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:207:in 'block in DEBUGGER__::Session#activate'
nil
#<Encoding::CompatibilityError: invalid byte sequence in US-ASCII>
@@@ #<Thread:0x00000001026daf80 run>
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:1248:in 'Thread#backtrace'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:1248:in 'block in DEBUGGER__::ThreadClient#wait_next_action_'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:1246:in 'Array#each'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:1246:in 'DEBUGGER__::ThreadClient#wait_next_action_'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:875:in 'block in DEBUGGER__::ThreadClient#wait_next_action'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:866:in 'block in DEBUGGER__::ThreadClient#fiber_blocking'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:866:in 'Fiber.blocking'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:866:in 'DEBUGGER__::ThreadClient#fiber_blocking'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:875:in 'DEBUGGER__::ThreadClient#wait_next_action'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:320:in 'DEBUGGER__::ThreadClient#suspend'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:251:in 'DEBUGGER__::ThreadClient#on_breakpoint'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/breakpoint.rb:69:in 'DEBUGGER__::Breakpoint#suspend'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/breakpoint.rb:170:in 'block in DEBUGGER__::LineBreakpoint#setup'
 > /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:2641:in 'Kernel#debugger'
 > -e:1:in '<main>'
["DEBUGGER Exception: /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/thread_client.rb:1252", #<Encoding::CompatibilityError: invalid byte sequence in US-ASCII>, ["/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:207:in 'String#strip!'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:207:in 'block in DEBUGGER__::Console#load_history'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:206:in 'Array#each'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:206:in 'DEBUGGER__::Console#load_history'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:183:in 'DEBUGGER__::Console#load_history_if_not_loaded'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:25:in 'DEBUGGER__::Console#readline_setup'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:100:in 'DEBUGGER__::Console#readline'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:78:in 'block in DEBUGGER__::UI_LocalConsole#readline'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:90:in 'block in DEBUGGER__::UI_LocalConsole#setup_interrupt'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:1989:in 'DEBUGGER__::Session#intercept_trap_sigint'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:83:in 'DEBUGGER__::UI_LocalConsole#setup_interrupt'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:77:in 'DEBUGGER__::UI_LocalConsole#readline'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:445:in 'DEBUGGER__::Session#wait_command'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:405:in 'block in DEBUGGER__::Session#wait_command_loop'", "<internal:kernel>:168:in 'Kernel#loop'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:404:in 'DEBUGGER__::Session#wait_command_loop'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:330:in 'DEBUGGER__::Session#process_event'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:255:in 'DEBUGGER__::Session#session_server_main'", "/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:207:in 'block in DEBUGGER__::Session#activate'"]]
/Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:207:in 'String#strip!': invalid byte sequence in US-ASCII (Encoding::CompatibilityError)
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:207:in 'block in DEBUGGER__::Console#load_history'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:206:in 'Array#each'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:206:in 'DEBUGGER__::Console#load_history'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:183:in 'DEBUGGER__::Console#load_history_if_not_loaded'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:25:in 'DEBUGGER__::Console#readline_setup'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/console.rb:100:in 'DEBUGGER__::Console#readline'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:78:in 'block in DEBUGGER__::UI_LocalConsole#readline'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:90:in 'block in DEBUGGER__::UI_LocalConsole#setup_interrupt'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:1989:in 'DEBUGGER__::Session#intercept_trap_sigint'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:83:in 'DEBUGGER__::UI_LocalConsole#setup_interrupt'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/local.rb:77:in 'DEBUGGER__::UI_LocalConsole#readline'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:445:in 'DEBUGGER__::Session#wait_command'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:405:in 'block in DEBUGGER__::Session#wait_command_loop'
	from <internal:kernel>:168:in 'Kernel#loop'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:404:in 'DEBUGGER__::Session#wait_command_loop'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:330:in 'DEBUGGER__::Session#process_event'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:255:in 'DEBUGGER__::Session#session_server_main'
	from /Users/naitoh/.rbenv/versions/3.4.1/lib/ruby/gems/3.4.0/gems/debug-1.10.0/lib/debug/session.rb:207:in 'block in DEBUGGER__::Session#activate'

Expected behavior

It should work as follows.

$ ruby -e 'puts Encoding.default_external' 
UTF-8
$ ruby -e 'require "debug"; debugger' 
# No sourcefile available for -e
=>#0	<main> at -e:1
(rdbg)