add test

Author: yjunechoe

tests/testthat/test-ggproto.R

@@ -10,3 +10,24 @@ test_that("construction checks input", {
   expect_snapshot_error(ggproto("Test", NULL, a <- function(self, a) a))
   expect_snapshot_error(ggproto("Test", mtcars, a = function(self, a) a))
 })
+
+test_that("all ggproto methods start with `{` (#6459)", {
+
+  ggprotos <- Filter(
+    function(x) inherits(x, "ggproto"),
+    mget(ls("package:ggplot2"), asNamespace("ggplot2"), ifnotfound = list(NULL))
+  )
+
+  method_nobrackets <- lapply(ggprotos, function(x) {
+    Filter(
+      function(m) inherits(x[[m]], "ggproto_method") && {
+        b <- as.list(body(get(m, x)))
+        length(b) == 0 || b[[1]] != quote(`{`)
+      },
+      ls(envir = x)
+    )
+  })
+
+  expect_length(Filter(length, method_nobrackets), 0)
+
+})