Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13 inch baking pan.
In a medium bowl, stir together the flour, sugar, baking soda and salt. Add the eggs, oil, pineapple and vanilla, mix until well blended. Pour into the prepared pan.
Bake for 30 to 35 minutes in the preheated oven, until a toothpick inserted comes out clean.
To make the topping: In a small saucepan, combine 1/2 cup sugar, pecans, butter, evaporated milk, 1 teaspoon vanilla and 1 cup coconut. Cook over medium heat, stirring occasionally, until the mixture thickens. Poke holes in the cake with a fork, then pour the warm mixture over the cake.