"Bon/bonne chance!": spelling and loanword specifics?

The adjective bon crossed over the Channel "in phrases such as bon apétit (1860), literally "good appetite;" bon-ton (1744) "good style;" bon mot." (Online Etymology Dictionary) Also with bon, bon-accord, bon(-)vivant, bon voyage etc.

The OED1(NED) refers to the "bon, bone, BOON q.v." form. Then the boon (būn) entry says used especially with originally French phrases. So you had bone (and bonne as a variant), like in bone chere, and bone fortune. Yet after the 16th, the NED explains the form was mostly dropped.

Books yields ngrams for both bon/bonne chance; the former, similar to the earlier phrases (i.e. bon voyage), and the latter, spelled like in the source language and sometimes appearing in quotation marks in the output. The pronunciation of bon can vary (bɒn, bɔn, bɔːn), and overlap that of the noun bonne (/bɔn/, i.e. the maid).

• Do you write bon chance or bonne chance? Does the modern OED carry/reference/distinguish either? Is it sufficiently in use to say?
• Is bon chance a partial borrowing, a semantic calque, an example of phono-semantic matching in loanword translation? How does borrowing generally deal with the peculiarities of the source language, such as grammatical gender?

Solution 1:

Bonne chance. I agree with Peter Shor: if we want to use someone else's language, I think we should do it the proper way, which means their way. I love both English and French and - whatever any book says - I think we should never use a masculine adjective with a feminine noun.

Solution 2:

Living as I do on the border with Quebec, and working daily within it's lovely confines... I'd get a can 'o whoopass handed to me if I were to butcher their language with "Bon chance" ! lol.

If you borrow a foreign phrase - much as if you borrow my lawnmower - you should return it undamaged!