The Shop Around the Corner is a 1940 Ernest Lubitsch film starring Jimmy Stewart, Margaret Sullavan and Frank Morgan.
Time has it as one of their best 100 films. EW says it "may be the wisest romance ever put on celluloid". The New York Times says,
So there it is, and a pretty kettle of bubbling brew it makes under Mr. Lubitsch's deft and tender management and with a genial company to play it gently, well this side of farce and well that side of utter seriousness. Possibly the most surprising part of it is the adaptability of the players to Mr. Lubitsch's Continental milieu whose splendid evocation is one of the nicest things of the picture. But they all have become natural figures against a natural background
TCM has an overview.