Check use of NULL in metadata arguments

[bms63]

[EeethB]

Some more context from my own testing:

• Example from xportr_metadata() runs fine without metadata:

metadata <- data.frame(
  dataset = "test",
  variable = c("Subj", "Param", "Val", "NotUsed"),
  type = c("numeric", "character", "numeric", "character"),
  format = NA,
  order = c(1, 3, 4, 2)
)

adlb <- data.frame(
  Subj = as.character(123, 456, 789),
  Different = c("a", "b", "c"),
  Val = c("1", "2", "3"),
  Param = c("param1", "param2", "param3")
)

xportr_metadata(adlb, metadata, "test")
xportr_metadata(adlb, domain = "test") # metadata will be NULL

• Example from xportr_type() gives an error if metadata is not set prior with xportr_metadata() or explicitly in call to type:

metadata <- data.frame(
  dataset = "test",
  variable = c("Subj", "Param", "Val", "NotUsed"),
  type = c("numeric", "character", "numeric", "character")
)

.df <- data.frame(
  Subj = as.character(123, 456, 789),
  Different = c("a", "b", "c"),
  Val = c("1", "2", "3"),
  Param = c("param1", "param2", "param3")
)

# These two work fine
xportr_type(.df, metadata, "test")
xportr_metadata(.df, metadata, "test") %>%
  xportr_type()

# This tells you to set metadata somewhere, even though the `metadata` default is NULL
xportr_type(.df, domain = "test")

Given that the error is descriptive, and dropping the NULL default for metadata would complicate some pipelines that xportr_metadata() is meant to simplify, we're leaving this as is for now. It will be revisited in the next development push.

[bms63]

Thanks for taking a look!!