Document expression arrays and text functions

[mwinters0]

I want to write a spam rule that allowlists a given domain if it is present in any header address. The expressions docs left me with many more questions.

Problem 1: Global variables is unclear about variable types.

• How are header variables like cc handled when they contain multiple values? Is this a single long string (the entire header value) or does Stalwart split these into an array of strings?

Problem 2: Email functions doesn't explain if or how text functions handle arrays.

• The ends_with docs (and all other text functions) say that they accept a string, not an array of strings.
• Given this example: ends_with(cc.domain, 'example.com') when there are multiple cc'ed addresses:
  • Is cc.domain an array or a string?
  • If it's an array, is this even legal?
  • If it's legal, is ends_with evaluated once per array element?
  • If so, is the expression true when all domains match (AND) , or when any match (OR)?
  • If this is OR, then how can I express an AND across all haystack elements?
• If the "haystack" can be an array, then can the "needle" be too?
  • Example: ends_with(cc.domain, ['foo.com', 'bar.com'])
  • Is this like Sieve where the expression is true if any haystack matches any needle?
• Can the haystack be an array of arrays?
  • Example: ends_with([from.domain, to.domain. cc.domain], ['foo.com', 'bar.com'])