Unlike geda-gaf, Lepton EDA supports attributes with empty values since version 1.9.17.
Since the fork, several new attributes have been introduced in Lepton. They may not be supported in the legacy code of geda-gaf.\
The attribute symbol= changes meaning of symbols in schematic,
that is, the way how lepton-netlist treats them. Such symbols will be
processed in a special way, not as ordinary components.
The reason is that graphical=1 attribute is overloaded and the netlister has to use various tricks (e.g. in DRC) to make things done.
symbol=nc means that the symbol will be treated as a no-connect symbol. The netlister won’t output its connection in the full list of schematic connections. DRC will suppress errors on connections having only one pin connected to such a symbol. The attribute is equivalent to the legacy set of attributes as follows:
graphical=1 device=DRC_Directive value=NoConnection
Other possible future uses of the symbol= attribute are given below.
Not implemented yet.
The attribute could be used to filter out power symbols from schematic components.
It could replace the net= and graphical= attributes, as well as some DRC attributes, to make the DRC logic more strict, and solve some net renaming issues.
Not implemented yet.
The attribute could be used to mark ports in hierarchical schematics in order to simplify the netlister logic.