be fussy about margin input length

Author: teunbrand

R/margins.R

@@ -8,6 +8,20 @@
 margin <- S7::new_class(
   "margin", parent = S7::new_S3_class(c("simpleUnit", "unit", "unit_v2")),
   constructor = function(t = 0, r = 0, b = 0, l = 0, unit = "pt") {
+    lens <- c(length(t), length(r), length(b), length(l))
+    if (any(lens != 1)) {
+      incorrect <- c("t", "r", "b", "l")[lens != 1]
+      s <- if (length(incorrect) > 1) "s" else ""
+      cli::cli_warn(c(
+        "In {.fn margin}, the argument{s} {.and {.arg {incorrect}}} should \\
+        have length 1, not length {.and {lens[lens != 1]}}.",
+        i = "Argument{s} get(s) truncated to length 1."
+      ))
+      t <- t[1]
+      r <- r[1]
+      b <- b[1]
+      l <- l[1]
+    }
     u <- unit(c(t, r, b, l), unit)
     S7::new_object(u)
   }

tests/testthat/_snaps/theme.md

@@ -61,6 +61,17 @@
       Error in `method(merge_element, list(ggplot2::element, class_any))`:
       ! Only elements of the same class can be merged.
 
+# margins() warn against wrong input lengths
+
+    Code
+      margin(c(1, 2), 3, 4, c(5, 6, 7))
+    Condition
+      Warning:
+      In `margin()`, the arguments `t` and `l` should have length 1, not length 2 and 3.
+      i Arguments get(s) truncated to length 1.
+    Output
+      [1] 1points 3points 4points 5points
+
 # Theme elements are checked during build
 
     `plot.title.position` must be one of "panel" or "plot", not "test".

tests/testthat/test-theme.R

@@ -473,6 +473,10 @@ test_that("titleGrob() and margins() work correctly", {
   expect_equal(width_cm(g10), width_cm(g1) + 2)
 })
 
+test_that("margins() warn against wrong input lengths", {
+  expect_snapshot(margin(c(1, 2), 3, 4, c(5, 6, 7)))
+})
+
 test_that("provided themes explicitly define all elements", {
   elements <- names(.element_tree)