punctuation - Post-hyphenation of split compound words

Assuming that these two words

off-topic

on-topic

must be hyphenated, which of the punctuations in the following sentences is correct? (crucial part emphasized)

Regardless of whether it is an off or on-topic example, it is a brilliant consideration in the definition of this proposal.

Regardless of whether it is an off- or on-topic example, it is a brilliant consideration in the definition of this proposal.

I know you can get around this with a verbose constuction like off-topic or on-topic, or by not hyphenating either and treating off and on and topic as separate words, but neither suggestion really does anything to answer my question.

Answer

The standard way to deal with this in English is your second example, "off- or on-topic". Another example of where the hyphen would be preserved for both forms of the hyphenated word might be pre- and post-, e.g.

The pre- and post-match responses of the soccer fans were markedly different.