Pour juice from canned tomatoes into a skillet. Add water or vegetable broth as necessary to achieve a thin layer of liquid. Add onions and garlic, if using, and sauté over high heat until onions are translucent, about 2 minutes. Turn off heat, adding more liquid so you have a thin layer again. Pull tomatoes apart with your fingers (careful--they squirt liquid!) into bite-sized pieces and place them in the skillet.
Add mushrooms and 1 tsp Italian seasoning and stir to combine. Sauté over high heat (cover if necessary to prevent splashing) and continue to cook until mushrooms are soft and light brown. Add wine and another 1 tsp Italian seasoning, uncover, and cook until liquid reduces by half, about 3 minutes.
Just before it's done, add capers and remaining 1/2 tsp Italian seasoning, stirring to combine. Season with salt and black pepper, then stir in chickpeas and serve.