Re: Lua filters: validating input and output formats

[Albert Krewinkel <albert+pandoc-9EawChwDxG8hFhg+JK9F0w@public.gmane.org>]

BPJ <melroch-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:

> I'm writing a filter which walks a table read from CSV, which are all
> read in as literal strings by Pandoc, and parses them with pandoc.read.
> In order to know which format to read the filter inspects a metadata
> field expecting the value to be the one to pass as second argument to
> pandoc.read. However there is easy way to validate that value before
> calling pandoc.read. To be sure I could create a table mapping every
> name returned by --list-input-formats to `true`, but it would seem that
> rather than every filter which needs this information (and conversely
> output formats for pandoc.write) maintaining its own lookup it would be
> better if the Lua API provided it, either as a pair of functions
> returning true if their argument is a valid format, or as (objects
> which act as) tables (sets) with valid formats mapped to true, which is
> something I assume Pandoc already has provision for internally. Does
> this seem like a good idea, or is my use case with the filter taking
> this info from the user too unusual to warrant this?

That seems like a good idea to me. I've created a PR:
https://github.com/jgm/pandoc/pull/8177