I've long believed (because I'd read it) that the film was begun before the German occupation, and production was interrupted, until after the liberation. From what I've read on here, though, it seems that it was filmed DURING the occupation, too. Is that right?
Carpe Noctem!
Yes, much the larger part of the actual filming - and all of the prepaparations - took place before D-Day. Admittedly much of this wasn't shot in Paris, a sizable part was done in and around Nice during the spring and summer of 1943. Nice was in Vichy France and not technically occupied, but still Vichy was a German puppet state that would do the bidding of Hitler and his henchmen.
Some of the film crew had resistance connections (including Prèvert, the main writer) and there's even a line during the opening credits about some persons - one of them Alexandre Trauner I think, who designed the amazing outdoor and indoor sets - "taking part from the underground" ('dans la clandestinité')! Trauner was a Jew and he lived (under an assumed name) with Carné and Prévert for the six months it took them to prepare the script; of course he had to be around some during the actual shoot as well. It's really astounding that this film could be made under the occupation.
You are a lunatic, Sir, and you're going to end up on the Russian front. I have a car waiting.
Strausszek said it all, or almost : when preparation and then shooting began, "Vichy" France was all German-occupied, since the nazi broke the "ligne de démarcation" in november 42, as an answer to the allied invasion of French North-Africa.
But fortunately, the city of Nice -where stood the "studios de la Victorine", the place of the shooting- was to be occupied by German allies, Mussolini's Italy, whose ruling ways on occupied territories were notoriously less heavy than the Germans' ones.
Alas!… On september of 43, Italy surrendered to the Allies… and the French "Italian occupation zone" switch to German rule, and Nice too.
Anyway, at that time, as far as I know (had they began to work under Italian rule? After all, "Les Visiteurs du soir" were made there, the year before), the production team went to Paris to the "studios Francoeur", and knew all the problems the other crews working for French cinema had at this moment in Paris and outskirts, bombings, shortages, and starvation. To understand them, have a look to the very good and interesting "Laissez-passer", a Bertrand Tavernier's movie dealing with these matters.
A last thing : the shooting going on until the "libération" (august of 44) and beyond, one of the actors, the great Robert Le Vigan (see him in "Goupi mains rouges", an absolute must), compromised in collaboration, chose to flee with the puppet government in Germany. He was replaced by Pierre Renoir. According to what I read, Carné says that Le Vigan had only shot one scene.
… Allright, I found something here : http://www.dvdclassik.com/critique/les-enfants-du-paradis-carne
It says that shootings began mid-summer 43 at studios la Victorine, then there was an interrumption for many reasons, and the shooting went again, this time in Paris, studio Pathé, rue Francoeur, and then in the studios of Joinville, in the suburbs (there were many filming lots in and around Paris, at that time).
The movie premiered on March 45, when the war was still going on --but in Germany now.