We reexamine nonequilibrium thermodynamics of multi-component fluids that undergo chemical reactions and reveal how to describe it in the context of GENERIC (general equation for the nonequilibrium reversible-irreversible coupling) framework. In the former part of this paper, we study monomer solutions. The independent variables are chosen so that the symmetry in the thermodynamic description of the mixed solution is kept, while avoiding the redundancy in the independent variables that describe the system. In the latter part of this paper, we apply this approach to polymer solutions. One of the species of the solution is the unreactive polymer chain represented by the bead-spring model. The polymer solution is neither dilute nor ideal. We construct the solution entropy so that the contributions from mixing and chain conformation are fully separated. The pressure tensor derived from such entropy with the help of the degeneracy requirement is slightly different from that derived previously for a dilute polymer solution. We discuss how the difference occurs.