Support for conditional directives

[martijnversluis]

Conditional directives

All directives can be equipped with a selector by appending a selector name to the name of the directive, separated by a dash (hyphen) -. If the selector fails, the directive is skipped.

For example:

{define-ukulele Dm base-fret 1 frets 2 2 1 0}
{define-guitar  Dm base-fret 1 frets x 0 3 2 3 1}

This will define the appropriate Dm chord for either ukulele or guitar.

Selection can be reversed by appending a ! to the selector.

How selectors are defined depends on the ChordPro processing tool. The ChordPro program uses the config values for instrument.type and user.name.

See https://www.chordpro.org/chordpro/chordpro-directives/#conditional-directives

• parse selector on Tag
• store selector on Line and Paragraph
• allow testing the condition
• allow ! for reversing the selector
• render sections conditionally based on selector
• set metadata conditionally based on selector
• return chord definitions conditionally