Provide better error message when adding unnamed attrib values

R/tags.R

@@ -292,7 +292,14 @@ tagFunction <- function(func) {
 #' @export
 tagAppendAttributes <- function(tag, ...) {
   throw_if_tag_function(tag)
-  tag$attribs <- c(tag$attribs, dropNullsOrEmpty(dots_list(...)))
+  newAttribs <- dropNullsOrEmpty(dots_list(...))
+  if (any(names2(newAttribs) == "")) {
+    stop(
+      "At least one of the new attribute values did not have a name.\n",
+      "Did you forget to include an attribute name?"
+    )
+  }
+  tag$attribs <- c(tag$attribs, newAttribs)
   tag
 }
 
@@ -492,6 +499,13 @@ tagWrite <- function(tag, textWriter, indent=0, eol = "\n") {
 
   # write attributes
   for (attrib in names(attribs)) {
+    # Can not display attrib without a key
+    if (identical(attrib, "")) {
+      stop(
+        "An attribute value did not have a name.\n",
+        "Did you forget to name your attribute value?"
+      )
+    }
     attribValue <- attribs[[attrib]]
     if (!is.na(attribValue)) {
       if (is.logical(attribValue))

tests/testthat/test-tags.r

@@ -399,6 +399,25 @@ test_that("Adding attributes to tags", {
   )
 })
 
+test_that("Adding unnamed attributes creates a warning", {
+  expect_error(
+    tagAppendAttributes(
+      tags$div(),
+      "value"
+    ),
+    "include an attribute name"
+  )
+
+  x <- div()
+  x$attribs[[1]] <- "value"
+  expect_error(
+    print(x),
+    "name your attribute value"
+  )
+})
+
+
+
 test_that("Testing for attributes on tags", {
   t1 <- tags$div("foo", class = "c1", class = "c2", id = "foo")