sql_case_when() doesn't support unevaluated formulas

[lionel-]

Reprex from @FrancoisGuillem in tidyverse/dplyr#3936

library(RSQLite)
library(rlang)
library(dplyr)

con <- dbConnect(SQLite(), ":memory:")
dbWriteTable(con, "mtcars", mtcars)

mtcars_remote <- tbl(con, "mtcars")

# Works
labels <- c("low", "mid", "high")
breaks <- c(2, 4)

cases <- lapply(seq_along(breaks), function(i) {
  expr(carb <= breaks[!!i] ~ labels[!!i])
})

cases <- append(cases, expr(TRUE ~ labels[length(labels)]))

mtcars %>% mutate(cg = case_when(!!!cases))
## => works
mtcars_remote %>% mutate(cg = case_when(!!!cases))
## Error in eval_bare(call, env) : 
##   'rho' must be an environment not NULL: detected in C-level eval

[hadley]

Are there other changes to dplyr::case_when() that I should know about?

[hadley]

Slightly even more simple reprex:

library(dplyr, warn.conflicts = FALSE)

mf <- dbplyr::memdb_frame(abc = 1:10)

fs1 <- rlang::exprs(
  abc == 4 ~ TRUE,
  TRUE     ~ FALSE
)
mf %>% mutate(case_when(!!!fs1)) %>% pull()
#>  [1] 0 0 0 1 0 0 0 0 0 0

x <- 4
fs2 <- rlang::exprs(
  abc == x ~ TRUE,
  TRUE     ~ FALSE
)
mf %>% mutate(case_when(!!!fs2)) %>% pull()
#> Error: Can't extract an environment from NULL

^{Created on 2019-01-02 by the reprex package (v0.2.1)}

[hadley]

Even simpler reprex:

partial_eval(expr(~ x))
#> Error: Can't extract an environment from NULL