I pretty squarely disagree with Rob Pike on that one. Copying is how you introduce bugs and insulate yourself from upstream bugfixes. I'm suggesting that you should try to remove code first, add a dependency on well-trusted code if that doesn't work, and only copy/reinvent as a last resort.
> I pretty squarely disagree with Rob Pike on that one.
TBH that's kind of an indication that you should rethink your position. Rob Pike has a lot of experience, he's seen a lot, and he knows what he's doing. I'm not saying you're wrong, just that you shouldn't snap to the defensive position.
Rob Pike's authority does not counter the negative experience I've had with vendoring dependencies, making local changes, and drifting so far from upstream that it becomes extremely difficult to merge in bugfixes. Or the positive experience I've had with package managers making it easy to bring in third-party code, easier than copying it in.
Deference to authority is a funny thing eh? I find that in life, and especially in running my business, I pretty frequently lock horns with people who disagree with me on account of a seemingly differing opinion of some other Experienced Person(R). It's like, such and such person has lots of experience in the industry, therefore they know the answer to this specific question better than you do, regardless of anything. When I hear these appeals to authority I always think that if I were actually sitting across the table from this Very Smart Person--as opposed to the person citing them--and they were willing to listen, we would probably end up in agreement. Like you say, the person might be WAY smarter than me in general, but... LOOK AT THE FUCKING DATA.
There's a reason smart people are good at solving problems, and it's not because they always defer to what other people 'know' to be true!
For me, that means I listen carefully for wisdom but have to speak louder when countering their occasional bullshit. Copying is considered a code smell by the likes of Fowler due to the problems it leads to. Also leads to bloat and performance issues. Better to cleanly, simply package up reusable solutions to problems like JSON or protocols (eg HTTP) then just keep importing the same one. You get lean apps plus a greater understanding of what they're doing.
And so does the person you hire down the line to extend that app. Never forget that part when talking copying and tweaking code. :)
