Parseability of trailing parameters of certain numeric replies

[jwodder]

The following numeric replies include information in their trailing parameters that a client would likely want to extract programmatically, but said parameters are represented as human-friendly text — but, on the other hand, the documentation for these replies does not state that the text used in these parameter may vary or should not be machine-parsed. Is this an oversight, or is it acceptable for a client to parse the trailing parameters of these replies? If the latter, exactly what formats can the parameters be expected to take?

• RPL_LUSERCLIENT
• RPL_LUSERME
• RPL_LOCALUSERS¹
• RPL_GLOBALUSERS¹
• RPL_WHOISCERTFP
• RPL_WHOISHOST
• RPL_WHOISMODES

Footnotes

1. I am aware that RPL_LOCALUSERS and RPL_GLOBALUSERS replies should include the relevant information as separate parameters for machine-parsing, but these parameters are not required, so when they're absent, is it acceptable to try to extract them from the trailing parameter instead? ↩ ↩²

[progval]

From https://modern.ircdocs.horse/#numerics:

Note that for numerics with “human-readable” informational strings for the last parameter which are not designed to be parsed, such as in RPL_WELCOME, servers commonly change this last-param text. Clients SHOULD NOT rely on these sort of parameters to have exactly the same human-readable string as described in this document. Clients that rely on the format of these human-readable final informational strings may fail. We do try to note numerics where this is the case with a message like “The text used in the last param of this message varies wildly”.

[jwodder]

@progval But how do I know whether a given parameter is "not designed to be parsed" unless the documentation says "The text used in the last param of this message varies wildly"? Or am I supposed to interpret that paragraph as saying that all human-readable informational trailing parameters are not designed to be parsed, regardless of whether the documentation says they vary or not?

[progval]

It says that in general it should not be parsed, and especially not when the documentation says that particular numeric "varies wildly".

[jwodder]

Then I think the current text is grammatically ambiguous, and I'd suggest rewriting the opening sentence of the paragraph to something like:

Note that some numerics, such as RPL_WELCOME, have “human-readable” informational strings for the last parameter; these strings are not designed to be parsed, and servers commonly change such last-param texts.