fix issue with 'SIGINT' handling in LineEditor#reset

[luke-gru]

@old_trap is the string "DEFAULT" and not a callable object (Proc)
if there are no other signal handlers for SIGINT signal to chain.

Found running 'make test-all' running Ruby's test suite and CTRL-C'ing the terminal, resulted in NoMethodError 'call' on string "DEFAULT".

[ghost]

in 9d95ae8 ; the code-

def reset(prompt = '', encoding = Encoding.default_external)

    @rest_height = (Reline::IOGate.get_screen_size.first - 1) - Reline::IOGate.cursor_pos.y

    @screen_size = Reline::IOGate.get_screen_size

    reset_variables(prompt, encoding)

    @old_trap = Signal.trap('SIGINT') {

      scroll_down(@highest_in_all - @first_line_started_from)

      Reline::IOGate.move_cursor_column(0)

      @old_trap.call if @old_trap.respond_to?(:call) # can also be string, ex: "DEFAULT"

    }

  end

explaining the code

old_trap is a function or object.

old_trap.respond_to?(:call) means check if function of old_trap called respond_to does has attribute call. so old_trap has call.
->
@old_trap.respond_to?(:call) means check if function of old_trap called respond_to has instance variable call or is old_trap the instance variable?
->
@old_trap.call if @old_trap.respond_to?(:call) means execute old_trap.call if @old_trap.respond_to?(:call) evaluates to true.

and all this is inside the braces in @old_trap = Signal.trap('SIGINT') { ... } , so assigned to old_trap and that's what is used by other functions.

---

[luke-gru]

@snow8gaia Sorry, I don't understand your comment.

[ghost]

I don't fully understand how this pull request fixes this? Its great that it does.

For eg:-

Found running 'make test-all' running Ruby's test suite and CTRL-C'ing the terminal, resulted in NoMethodError 'call' on string "DEFAULT"

So, you ran make test-all in order to run Ruby's test-suite. Then pressed CTRL+C while in the terminal; that resulted in a NoMethodError call on string "DEFAULT".

@old_trap is the string "DEFAULT" and not a callable object (Proc)
if there are no other signal handlers for SIGINT signal to chain.

@old_trap is the string
its a string? is the string "DEFAULT" a valid signal that can be receive from the OS? why is old_trap calling a non-callable?

if there are no other signal handlers for SIGINT signal to chain.

so the SIGINT signal can't chain the functions. and the functions take strings as input.
other handler functions are absent, why?

---

Thanks anyways.

[ghost]

ignore the timing of my earlier comment pull/34#issuecomment-503693550. Just read your response to issue/34#issuecomment-50368544; can't reply now.