Fix edge case when coercing data frames to matrices

NEWS.md

@@ -1,5 +1,7 @@
 # dplyr (development version)
 
+* Fixed an edge case when coercing data frames to matrices (#7004).
+
 * Fixed an issue where duckplyr's ALTREP data frames were being materialized
   early due to internal usage of `ncol()` (#7049).
 

R/data-mask.R

@@ -11,7 +11,22 @@
       frame <- caller_env(n = 2)
       local_mask(self, frame)
 
-      names_bindings <- chr_unserialise_unicode(names2(data))
+      names <- names(data)
+
+      if (is.null(names)) {
+        cli::cli_abort(
+          "Can't transform a data frame with `NULL` names.",
+          call = error_call
+        )
+      }
+      if (vec_any_missing(names)) {
+        cli::cli_abort(
+          "Can't transform a data frame with missing names.",
+          call = error_call
+        )
+      }
+
+      names_bindings <- chr_unserialise_unicode(names)
       if (any(names_bindings == "")) {
         # `names2()` converted potential `NA` names to `""` already
         abort("Can't transform a data frame with `NA` or `\"\"` names.", call = error_call)

tests/testthat/_snaps/filter.md

@@ -243,7 +243,7 @@
       filter(df2)
     Condition
       Error in `filter()`:
-      ! Can't transform a data frame with `NA` or `""` names.
+      ! Can't transform a data frame with missing names.
 
 # can't use `.by` with `.preserve`
 

tests/testthat/_snaps/mutate.md

@@ -361,5 +361,5 @@
       mutate(df2)
     Condition
       Error in `mutate()`:
-      ! Can't transform a data frame with `NA` or `""` names.
+      ! Can't transform a data frame with missing names.
 

tests/testthat/_snaps/summarise.md

@@ -77,7 +77,7 @@
       summarise(df2)
     Condition
       Error in `summarise()`:
-      ! Can't transform a data frame with `NA` or `""` names.
+      ! Can't transform a data frame with missing names.
 
 # summarise() gives meaningful errors
 

tests/testthat/test-data-mask.R

@@ -0,0 +1,7 @@
+test_that("Empty matrix can be coerced to a data frame (#7004)", {
+  skip_if_not(getRversion() >= "4.4")
+  expect_equal(
+    slice(as.data.frame(matrix(nrow = 0, ncol = 0)), 1),
+    data.frame()
+  )
+})