From 173b4232bff810f563e1739211ea7545ed0651e6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kirill=20M=C3=BCller?= <krlmlr@users.noreply.github.com>
Date: Fri, 16 Aug 2024 02:23:48 +0200
Subject: [PATCH] Fix edge case when coercing data frames to matrices (#7070)

Closes #7004
---
 NEWS.md                            |  2 ++
 R/data-mask.R                      | 17 ++++++++++++++++-
 tests/testthat/_snaps/filter.md    |  2 +-
 tests/testthat/_snaps/mutate.md    |  2 +-
 tests/testthat/_snaps/summarise.md |  2 +-
 tests/testthat/test-data-mask.R    |  7 +++++++
 6 files changed, 28 insertions(+), 4 deletions(-)
 create mode 100644 tests/testthat/test-data-mask.R

diff --git a/NEWS.md b/NEWS.md
index 9df8a4c1e0..903031d296 100644
--- a/NEWS.md
+++ b/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).
 
diff --git a/R/data-mask.R b/R/data-mask.R
index b72a708289..b50aa182c3 100644
--- a/R/data-mask.R
+++ b/R/data-mask.R
@@ -11,7 +11,22 @@ DataMask <- R6Class("DataMask",
       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)
diff --git a/tests/testthat/_snaps/filter.md b/tests/testthat/_snaps/filter.md
index 3d24697ea5..39a0f26903 100644
--- a/tests/testthat/_snaps/filter.md
+++ b/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`
 
diff --git a/tests/testthat/_snaps/mutate.md b/tests/testthat/_snaps/mutate.md
index de71d9da8c..8c4c2f7de7 100644
--- a/tests/testthat/_snaps/mutate.md
+++ b/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.
 
diff --git a/tests/testthat/_snaps/summarise.md b/tests/testthat/_snaps/summarise.md
index 3f80a60a5a..8040d43a9d 100644
--- a/tests/testthat/_snaps/summarise.md
+++ b/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
 
diff --git a/tests/testthat/test-data-mask.R b/tests/testthat/test-data-mask.R
new file mode 100644
index 0000000000..e82f4b4b08
--- /dev/null
+++ b/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()
+  )
+})