main: filter_output loses line prefixes

If the watched process ends a push to the pipe without a newline at the
end, but with newlines in the middle, then sep_rx.split() will return
with multiple entries, the last of which will not end with a newline
and yet not be the empty string.  This line prefix needs to be stashed
into the pending buffer, too.

This turns out to be exactly the same logic as if sep_rx.split had not
split the string, so eliminate one layer of conditionals.

This version incorporates feedback from Rob Browning to continue to pass
a list to extend().

Signed-off-by: Nathaniel Filardo <[email protected]>

main.py

@@ -204,16 +204,15 @@ def filter_output(src_out, src_err, dest_out, dest_err):
                     print_clean_line(dest, pending.pop(fd, []), width)
                 else:
                     split = sep_rx.split(buf)
-                    if len(split) > 2:
-                        while len(split) > 1:
-                            content, sep = split[:2]
-                            split = split[2:]
-                            print_clean_line(dest,
-                                             pending.pop(fd, []) + [content],
-                                             width,
-                                             sep)
-                    else:
-                        assert(len(split) == 1)
+                    while len(split) > 1:
+                        content, sep = split[:2]
+                        split = split[2:]
+                        print_clean_line(dest,
+                                         pending.pop(fd, []) + [content],
+                                         width,
+                                         sep)
+                    assert(len(split) == 1)
+                    if split[0] :
                         pending.setdefault(fd, []).extend(split)
     except BaseException as ex:
         pending_ex = chain_ex(add_ex_tb(ex), pending_ex)