  We present an updated analysis of the gamma-ray flux from the directions of
classical dwarf spheroidal galaxies, deriving new constraints on WIMP dark
matter (DM) annihilation using a decade of Fermi-LAT data. Among the major
novelties, we infer the dwarfs' J-factors by including new observations without
imposing any a priori parametric profile for the DM distribution. While
statistically compatible with results obtained from more conventional
parameterisations, this procedure reduces the theoretical bias imposed on the
data. Furthermore, we retain the full data-driven shape of the J-factors'
empirical probability distributions when setting limits on DM, without imposing
log-normality as is typically done. In conjunction with the data-driven
J-factors, we use a new method for estimating the probability distribution
function of the astrophysical background at the dwarf position, fully profiling
over background uncertainties. We show that, for most classical dwarfs, the
background systematic uncertainty dominates over the uncertainty on their
J-factors. Raw distributions of J- and D-factors (the latter being the
analogous of J-factors for decaying DM) are available upon request.
