Preheat the oven to 350 degrees F (175 degrees C). Spray 18 cups of a muffin tin with nonstick cooking spray that contains flour. Mix flour, sugar, chocolate chips, baking powder, and salt together in a large bowl. Place ricotta cheese in a bowl and add eggs, 1 at a time, beating well after each addition. Whisk in milk and vanilla extract until blended. Fold cheese mixture and canola oil into flour mixture until just blended. Spoon batter evenly into the prepared muffin cups. Bake in the preheated oven until a toothpick inserted in the center of a muffin comes out clean, 22 to 25 minutes. Remove muffins from the pan immediately and let cool on a wire rack.