Issue 122: Check family input valid (#144)

      * Add string and LPDF checker for epidist_family

* Add unit tests

* Correct the namespace handling

* Remove whitespace

DESCRIPTION

@@ -33,7 +33,9 @@ Imports:
     ggridges,
     here,
     stats,
-    cli
+    cli,
+    checkmate,
+    rstan
 Suggests:
     bookdown,
     testthat (>= 3.0.0),

R/latent_individual.R

@@ -61,11 +61,24 @@ epidist_formula.epidist_latent_individual <- function(data, delay_central = ~ 1,
   return(form)
 }
 
+#' @importFrom rstan lookup
 #' @method epidist_family epidist_latent_individual
 #' @family latent_individual
 #' @export
 epidist_family.epidist_latent_individual <- function(data, family = "lognormal",
                                                      ...) {
+  checkmate::assert_string(family)
+
+  pdf_lookup <- rstan::lookup("pdf")
+  valid_pdfs <- gsub("_lpdf", "", pdf_lookup$StanFunction)
+  if (!family %in% valid_pdfs) {
+    cli::cli_warn(
+      "The provided family {.code family} does not correspond to a valid LPDF
+      function available in rstan. (It is possible [but unlikely] that there is
+      such an LPDF in Stan available via cmdstanr, as rstan is behind Stan.)"
+    )
+  }
+
   brms::custom_family(
     paste0("latent_", family),
     dpars = c("mu", "sigma"),

tests/testthat/test-unit-latent_individual.R

@@ -55,6 +55,11 @@ test_that("epidist_family.epidist_latent_individual with default settings produc
   expect_s3_class(family, "family")
 })
 
+test_that("epidist_family.epidist_latent_individual warns users or gives an error when passed inappropriate family input", { # nolint: line_length_linter.
+  expect_error(epidist_family(prep_obs, family = 1))
+  expect_warning(epidist_family(prep_obs, family = "not_a_real_lpdf"))
+})
+
 test_that("the family argument in epidist_family.epidist_latent_individual passes as expected", { # nolint: line_length_linter.
   family_gamma <- epidist_family(prep_obs, family = "gamma")
   expect_equal(family_gamma$name, "latent_gamma")