Filter backtrace before format in handle_exception

handle_exception now applies the filter_backtrace to exception
backtraces prior to formatting the lines with Exception#full_message

This fixes a bug in upstream projects, notably Rails, where the
backtrace filtering logic expects the lines to be formatted as
Exception#backtrace.

Co-authored-by: Hartley McGuire <[email protected]>

lib/irb.rb

@@ -1216,12 +1216,15 @@ def encode_with_invalid_byte_sequence(str, enc)
     end
 
     def handle_exception(exc)
+      exc = exc.dup
       if exc.backtrace[0] =~ /\/irb(2)?(\/.*|-.*|\.rb)?:/ && exc.class.to_s !~ /^IRB/ &&
          !(SyntaxError === exc) && !(EncodingError === exc)
         # The backtrace of invalid encoding hash (ex. {"\xAE": 1}) raises EncodingError without lineno.
         irb_bug = true
       else
         irb_bug = false
+        backtrace = exc.backtrace.map { |l| @context.workspace.filter_backtrace(l) }.compact
+        exc.set_backtrace(backtrace)
       end
 
       if RUBY_VERSION < '3.0.0'
@@ -1246,7 +1249,6 @@ def handle_exception(exc)
           lines = m.split("\n").reverse
         end
         unless irb_bug
-          lines = lines.map { |l| @context.workspace.filter_backtrace(l) }.compact
           if lines.size > @context.back_trace_limit
             omit = lines.size - @context.back_trace_limit
             lines = lines[0..(@context.back_trace_limit - 1)]