It looks good, but non-mandatory fields have an ID of -1, so it
doesn't actually work. Some places got around this by converting
the ID to unsigned, but this just hides the real issue from
unsuspecting coders.
Fixes https://gitlab.com/kicad/code/kicad/issues/4140
Please note that the symbol cache is not embedded in the schematic file
to allow for round robin testing with the existing file format. Once
the parser round robin testing is complete, the symbol cache will be
embedded in the schematic file.
This implements all existing symbol library object support and the ability
to save and load symbol library files between file formats for round robin
testing.
CHANGES: Symbol library file format has been converted to s-expressions.
Add support code for picking apart symbols at some future junction that
will allow full inheritance conversion of existing symbol libraries. For
now, symbols arranged by unit and body style numbers are nested for round
robin testing of symbol libraries once the parser is complete.