  Quark spin effects in hadronization have been recently included in the PYTHIA
8 event generator for the simulation of the deep inelastic scattering (DIS)
process off a polarized nucleon target via the external StringSpinner package.
The spin effects can be simulated for the production of pseudoscalar mesons
using the string+${}^3P_0$ model of polarized quark fragmentation and
parametrizations of the transversity PDFs. We present here a major development
of StringSpinner which includes the production of vector mesons in the
polarized PYTHIA 8 string fragmentation as well as their polarized decays. The
package is validated and used to simulate the transverse-spin asymmetries in
semi-inclusive DIS (SIDIS). The simulation results on the Collins and dihadron
asymmetries for the final state mesons are compared with the asymmetries
measured in SIDIS off transversely polarized protons. Also shown are the
predictions for the Collins asymmetries for $\rho$ mesons produced in SIDIS off
transversely polarized protons.
