fix: Fail if "layout" attribute doesn't match the number of vertices

R/plot.R

@@ -142,6 +142,11 @@ plot.igraph <- function(
   }
 
   layout <- i.postprocess.layout(params("plot", "layout"))
+  if (nrow(layout) != vc) {
+    cli::cli_abort(c(
+      "The layout has {nrow(layout)} rows, but the graph has {vc} vertices.",
+    "i" = "It is recommended to store the layout as x and y vertex attributes and not as a matrix graph attribute."))
+  }
   margin <- params("plot", "margin")
   margin <- rep(margin, length.out = 4)
   rescale <- params("plot", "rescale")

tests/testthat/_snaps/plot.md

@@ -0,0 +1,9 @@
+# layout as graph attribute error works
+
+    Code
+      plot(g)
+    Condition
+      Error in `plot()`:
+      ! The layout has 5 rows, but the graph has 10 vertices.
+      i It is recommended to store the layout as x and y vertex attributes and not as a matrix graph attribute.
+

tests/testthat/test-plot.R

@@ -138,6 +138,15 @@ test_that("Edges stop at outside of rectangle node", {
   vdiffr::expect_doppelganger("rectangle-edges", rectangle_edges)
 })
 
+
+test_that("layout as graph attribute error works", {
+  g <- make_full_graph(10)
+  g$layout <- layout_in_circle(g)[1:5, ]
+  expect_snapshot(error = TRUE, {
+    plot(g)
+  })
+})
+
 test_that("Multi loops are arranged correctly", {
   skip_if_not_installed("vdiffr")