xgettext: Python: Add support for f-strings.
Reported by Ben <gnu@mail.qoben.com>
at <https://savannah.gnu.org/bugs/?61596>.
* gettext-tools/src/x-python.c (P7_498_START_OF_EXPRESSION): New macro.
(token_type_498, token_type_l498, token_type_m498, token_type_r498): New enum
items.
(free_token): Treat token_type_498 like token_type_string.
(phase7_getuc): Accept an f_string parameter. Use it to combine {{ to { and
}} to }.
(f_string_depth): New variable.
(struct f_string_level): New type.
(f_string_stack, f_string_stack_alloc): New variables.
(new_f_string_level): New function.
(open_pb): Renamed from open_pbb.
(phase5_get): Consider also the f_string_stack. Accept f"...", fr"...", rf"..."
syntax. Recognize tokens of type token_type_498, token_type_l498,
token_type_m498, token_type_r498.
(x_python_lex): Treat token_type_498 like token_type_string.
(extract_balanced): Handle the new token types.
(extract_python): Initialize f_string_depth and the f_string_stack.
* gettext-tools/tests/xgettext-python-1: Test also the backslash handling in
f-strings.
* gettext-tools/tests/xgettext-python-8: New file.
* gettext-tools/tests/Makefile.am (TESTS): Add it.
* gettext-tools/doc/lang-python.texi (Python): Explain the limitations of
f-string support.
* NEWS: Mention the change.
