library(bayestestR)
library(blavaan)

data("PoliticalDemocracy", package = "lavaan")

model <- "
  # latent variable definitions
  dem60 =~ y1 + a*y2
  dem65 =~ y5 + a*y6

  # regressions
  dem65 ~ dem60

  # residual correlations
  y1 ~~ y5
"

model2 <- "
  # latent variable definitions
  dem60 =~ y1 + a*y2
  dem65 =~ y5 + a*y6

  # regressions
  dem65 ~ 0*dem60

  # residual correlations
  y1 ~~ 0*y5
"
suppressWarnings(capture.output({
  bfit <- blavaan::bsem(model,
                        data = PoliticalDemocracy,
                        n.chains = 1, burnin = 50, sample = 100
  )
  bfit2 <- blavaan::bsem(model2,
                         data = PoliticalDemocracy,
                         n.chains = 1, burnin = 50, sample = 100
  )
}))

blavaan::blavCompare(bfit, bfit2)
#> Error in apply(diffs, 2, sum) : dim(X) must have a positive length