You are a goody-goody.
I am not too sure what is implied here. Is the translation correct?
The use of お前 makes me think that the sentence is confrontational, and the 〜さん honorific is used ironically or sarcastically.
So I wonder if this could mean “You are a smart-ass, aren’t you?” or “you are acting all obedient/innocent” (but I see through your act).
If I just read the Japanese sentence without the English one, I would interpret it as:
- (Talking to one’s pet): Oh, my lovely dog! What a great job (or how well-mannered you are)! You get a treat.
- (Talking to one’s colleague): I talked too straight to my boss and made his upset. But you are so smart that you just keep quiet.
お前 doesn’t always have a confrontational nuance. お前 is used when you adress someone mentally/socially close. For examle, “I love you!” can be translated as お前のことが大好きだ! No hostility here.
お + adjective + さん is a type of compound noun, meaning “one is the person who has the characteristics/quality of (adjective)”. So, お前はお利口さんだよ literally means “you are the one who is smart”. “Smart” (利口な) can be interpreted as either “capable” (as in example #1, dog case) or “manipulative/tactic” (as in example #2, shrewd colleague). It totally depends.
“Smart ass” with an ironical nuance is the interpretation of example #2, and “obedient” is of example #1.