modal verbs - Conditionals in the future

My colleague and I have a hot discussion about which is correct.

My version is:

If you don't fix the bug I will send you a patch.

and his one is:

I would send you a patch if you don't fix the problem.

Discussion context is: there is a bug in a project. I will send a patch in case that it will not be fixed this evening.

I've written mine following academic definitions of "future conditionals" and my colleague's version looks unnatural for me. So who is right? If neither - what would be a correct sentence?

Answer

Yours is the correct option, but not because of clause order. The main difference is that you use if ... then I will, and your friend uses I would... if.

Both the following are correct:

If you don't fix the bug I will send you a patch.

I will send you a patch if you don't fix the bug.

However, replacing the will with would makes either one incorrect, since the do in don't refers to an event which is likely to happen (known as First Conditional) and would refers to an event which is not likely to happen (known as Second Conditional). Since you are referring to events which are likely to happen, you should use don't and will. Otherwise you would use didn't and were.