Best answer here as it touches on inarguable facts rather than feelings. NOTE: Emotions are mainly a mammal thing, though reptiles and birds have a sort-of amygdala, not the same though.

And an interesting bit for OP: Dogs DO smile! At the least we can that we selected for more expressive facial muscles in dogs. In contrast, my pig has about zero emotional indicators, though he seems smarter than any dog I’ve met.

Dogs were shaped during the course of domestication both in their behavior and in their anatomical features. Here we show that domestication transformed the facial muscle anatomy of dogs specifically for facial communication with humans. A muscle responsible for raising the inner eyebrow intensely is uniformly present in dogs but not in wolves. Behavioral data show that dogs also produce the eyebrow movement significantly more often and with higher intensity than wolves do, with highest-intensity movements produced exclusively by dogs. Interestingly, this movement increases paedomorphism and resembles an expression humans produce when sad, so its production in dogs may trigger a nurturing response. We hypothesize that dogs’ expressive eyebrows are the result of selection based on humans’ preferences.

https://www.pnas.org/doi/10.1073/pnas.1820653116

Far more out there if you want less technical resources:

https://www.nbcnews.com/science/weird-science/dogs-faces-evolved-improve-connections-people-study-suggests-rcna22362