Use tidy dots in data_grid

Fixes #58

DESCRIPTION

@@ -18,7 +18,7 @@ Imports:
     tibble,
     broom,
     dplyr,
-    tidyr (>= 0.6.0)
+    tidyr (>= 0.8.0)
 Suggests:
     testthat,
     ggplot2,

NEWS.md

@@ -1,5 +1,7 @@
 # modelr 0.1.1.9000
 
+* `data_grid()` no longer fails with modern tidyr (#58).
+
 * Use more robust calculation of `rsquare()`: 1 - SS_res / SS_tot rather 
   than SS_reg / SS_tot (#37).
 

R/data-grid.R

@@ -30,7 +30,8 @@ data_grid <- function(data, ..., .model = NULL) {
 
   # Generate grid of typical values
   needed <- setdiff(predictor_vars(.model), names(expanded))
-  typical <- tidyr::crossing_(lapply(data[needed], typical))
+  typical_vals <- lapply(data[needed], typical)
+  typical_df <- tidyr::crossing(!!!typical_vals)
 
-  tidyr::crossing(expanded, typical)
+  tidyr::crossing(expanded, typical_df)
 }

tests/testthat/test-data-grid.R

@@ -0,0 +1,14 @@
+context("test-data-grid.R")
+
+test_that("can generate typical values", {
+  df <- tibble::tibble(
+    x = rep(c("a", "b"), each = 5),
+    y = rep(c("a", "b"), 5),
+    z = rnorm(10)
+  )
+  mod <- lm(z ~ x + y, data = df)
+  out <- data_grid(df, .model = mod)
+
+  expect_equal(out$x, c("a", "a", "b", "b"))
+  expect_equal(out$y, c("a", "b", "a", "b"))
+})