Commodity directive and format subdirective implementation

[darylwright]

• I'm submitting a ... [ ] bug report [ * ] feature request [ ] question about the decisions made in the repository [ ] question about how to use this project

• Summary

  • The commodity directive needs to be implemented as per the hledger documentation.
  • The format subdirective needs to be implemented alongside the commodity directive.
  • Subdirective comments are supported below the commodity directive in any order relative to the format subdirective (if present).
  • All other subdirectives are ignored and should not cause parsing errors.
  • We should examine other directives and how they handle subdirectives. Notably, the format subdirective should be ignored under all other directives and should not cause parsing errors.
  • Additionally, we should also implement the default commodity directive (or D directive) as it is functionally identical to a commodity directive without the format subdirective.

• Other information (e.g. detailed explanation, stack traces, related issues, suggestions how to fix, links for us to have context, eg. StackOverflow, personal fork, etc.)

  • N/A

[darylwright]

We should examine other directives and how they handle subdirectives. Notably, the format subdirective should be ignored under all other directives and should not cause parsing errors.

The format subdirective is invalid under the default commodity (D) directive. Subdirective comments are successfully parsed/ignored.

[darylwright]

Work is ongoing in https://github.com/darylwright/hledger-parser/tree/feature/commodity_directive

[darylwright]

Regarding the following points:

• All other subdirectives are ignored and should not cause parsing errors.
• We should examine other directives and how they handle subdirectives. Notably, the format subdirective should be ignored under all other directives and should not cause parsing errors.

This is something that concerns the behaviour of subdirectives in all top-level directives, and is therefore beyond the scope of this already large feature. It's debatable whether we should respect hledger behaviour here or not, especially given that it concerns subdirectives that are invalid anyway. This could also risk creating unnecessary clutter in the parsing diagrams, making them less readable. Disregarding the above two points for now.