pastry at a cafe

Only if you ask before sitting down.

Edit: to answer Tim’s question—yes, it’s acceptable in France. Some cafes don’t even have croissants in the morning or run out. It is not unusual to ask if they can get some or you can run to a bakery for something, so why not a breakfast sweet they don't serve

So yes, what you read is correct. I’ve done it with my French husband and French friends before. For form, you may want to order one of their croissants, as well, and enjoy both. It’s vacation.

I hope that answers Tim’s question: you read it and cultures are different.

If you wouldn’t do it here why would you do it there?

merci Bets.

We’ve done it many times. We’re very respectful and low-key about it when we do (which i’m sure you would be).

If you wouldn’t do it here why would you do it there?

Because it's different countries and different cultures.

We have only done this for cafes that don't have pastries. If they have a stack of croissants at the counter, it is considered bad form. It is easy enough to buy and eat pastries without doing it in someone's restaurant who is in the business of selling food. Occasionally there is a place that doesn't serve pastries only coffee in the morning and those places encourage people to bring their own -- ask of course.

I read somewhere that it is ok to bring a pastry to a cafe to eat with
my morning grand creme. My favorite cafe (because of it's sunny
location) only has croissants. Is it really acceptable to bring a
pastry from elsewhere to eat there? I certainly would never do that
here!

Be careful of things you "read somewhere". Accuracy sadly has no correlation with info floating out there.

Always ask permission first.