Fix style_extra_css, add heading arg, add tests

R/style_extra_css.R

 #'   `list(".class-id" = list("css-property" = "value"))`
 #' @param append If `TRUE` output will be appended to `outfile`; otherwise,
 #'   it will overwrite the contents of `outfile`.
+#' @param heading Heading added above extra CSS. Use `NULL` to disable.
 #'
 #' @examples
 #' style_extra_css(
 #' )
 #' @inheritParams style_xaringan
 #' @export
-style_extra_css <- function(css, outfile = "xaringan-themer.css", append = TRUE) {
-  x <- paste("\n\n/* Extra CSS */", list2css(css), sep = "\n")
+style_extra_css <- function(
+  css,
+  outfile = "xaringan-themer.css",
+  append = TRUE,
+  heading = "Extra CSS"
+) {
+  has_heading <- !is.null(heading)
+  x <- paste0(
+    if (has_heading) paste0("/* ", heading, " */\n"),
+    list2css(css)
+  )
+  if (append) x <- paste0(if (has_heading) "\n\n" else "\n", x)
   if (is.null(outfile)) return(x)
   cat(
     x,
     file = outfile,
-    append = TRUE,
+    append = append,
     sep = "\n"
   )
+  invisible(x)
 }
 
 #' @inheritParams style_extra_css

tests/testthat/test-list2css.R

-context("test-list2css.R")
-
-test_that("list2css converts lists to css", {
-  css <- list(
-    ".remark-slide" = list(
-      "color" = "#FFF",
-      "font-size" = "30px"
-    )
-  )
-  expected <- ".remark-slide {
-  color: #FFF;
-  font-size: 30px;
-}"
-  expect_equal(list2css(css), expected)
-
-  css[[".new-class"]] <- list("background-color" = "#000")
-  expected <- c(expected, ".new-class {\n  background-color: #000;\n}")
-  expect_equal(list2css(css), expected)
-})
-
-test_that("list2css errors if css list is not named", {
-  css <- list(list(
-    "color" = "#FFF",
-    "font-size" = "30px"
-  ))
-  expect_error(list2css(css))
-})
-
-test_that("list2css errors if css list has unnamed elements", {
-  css <- list(
-    list(
-      "color" = "#FFF",
-      "font-size" = "30px"
-    ),
-    ".test" = list(color = "red")
-  )
-  expect_error(list2css(css))
-})
-
-test_that("list2css errors if css list has unnamed properties", {
-  css <- list(
-    ".class" = list(
-      color = "#FFF",
-      "font-size" = "30px"
-    ),
-    ".test" = list("red")
-  )
-  expect_error(list2css(css))
-
-  css <- list(
-    ".class" = list(
-      "#FFF",
-      "font-size" = "30px"
-    ),
-    ".test" = list("red")
-  )
-  expect_error(list2css(css))
-})
-
-test_that("list2css errors if not list within list", {
-  css <- list(
-    ".class" = list(
-      list(color = "red"),
-      "font-size" = "30px"
-    ),
-    ".test" = list("red")
-  )
-  expect_error(list2css(css))
-})

tests/testthat/test-style_extra_css.R

+# test_that()
+
+describe("style_extra_css", {
+  css <- list(body = list(color = "#123"))
+
+  it("returns text if outfile is NULL", {
+    expect_equal(
+      style_extra_css(css, NULL),
+      "\n\n/* Extra CSS */\nbody {\n  color: #123;\n}"
+    )
+    expect_equal(
+      style_extra_css(css, NULL, heading = NULL),
+      "\nbody {\n  color: #123;\n}"
+    )
+    expect_equal(
+      style_extra_css(css, NULL, append = FALSE, heading = NULL),
+      "body {\n  color: #123;\n}"
+    )
+    expect_equal(
+      style_extra_css(css, NULL, append = FALSE, heading = "TEST TEST"),
+      "/* TEST TEST */\nbody {\n  color: #123;\n}"
+    )
+  })
+
+  tmpfile <- tempfile(fileext = ".css")
+  first <- style_extra_css(
+    css = list(.first = list(color = "#123")),
+    outfile = tmpfile,
+    append = FALSE,
+    heading = "First CSS"
+  )
+  first_exp <- "/* First CSS */\n.first {\n  color: #123;\n}"
+
+  it("writes text to the outfile", {
+    expect_equal(first, first_exp)
+    expect_equal(
+      readLines(tmpfile, warn = FALSE),
+      strsplit(first_exp, "\n")[[1]]
+    )
+  })
+
+  second <- style_extra_css(
+    css = list(.second = list(color = "#321")),
+    outfile = tmpfile,
+    append = TRUE,
+    heading = "Second CSS"
+  )
+  second_exp <- "\n\n/* Second CSS */\n.second {\n  color: #321;\n}"
+
+  it("appends to existing outfile", {
+    expect_equal(second, second_exp)
+    expect_equal(
+      readLines(tmpfile, warn = FALSE),
+      strsplit(paste0(first_exp, "\n", second_exp), "\n")[[1]]
+    )
+  })
+
+  third <- style_extra_css(
+    css = list(.third = list(color = "#333")),
+    outfile = tmpfile,
+    append = FALSE,
+    heading = "Third CSS"
+  )
+  third_exp <- "/* Third CSS */\n.third {\n  color: #333;\n}"
+
+  it("over writes text in the outfile if append=FALSE", {
+    expect_equal(third, third_exp)
+    expect_equal(
+      readLines(tmpfile, warn = FALSE),
+      strsplit(third_exp, "\n")[[1]]
+    )
+  })
+})
+
+describe("list2css()", {
+  it("converts lists to css", {
+    css <- list(
+      ".remark-slide" = list(
+        "color" = "#FFF",
+        "font-size" = "30px"
+      )
+    )
+    expected <- ".remark-slide {
+  color: #FFF;
+  font-size: 30px;
+}"
+    expect_equal(list2css(css), expected)
+
+    css[[".new-class"]] <- list("background-color" = "#000")
+    expected <- c(expected, ".new-class {\n  background-color: #000;\n}")
+    expect_equal(list2css(css), expected)
+  })
+
+  it("errors if css list is not named", {
+    css <- list(list(
+      "color" = "#FFF",
+      "font-size" = "30px"
+    ))
+    expect_error(list2css(css))
+  })
+
+  it("errors if css list has unnamed elements", {
+    css <- list(
+      list(
+        "color" = "#FFF",
+        "font-size" = "30px"
+      ),
+      ".test" = list(color = "red")
+    )
+    expect_error(list2css(css))
+  })
+
+  it("errors if css list has unnamed properties", {
+    css <- list(
+      ".class" = list(
+        color = "#FFF",
+        "font-size" = "30px"
+      ),
+      ".test" = list("red")
+    )
+    expect_error(list2css(css))
+
+    css <- list(
+      ".class" = list(
+        "#FFF",
+        "font-size" = "30px"
+      ),
+      ".test" = list("red")
+    )
+    expect_error(list2css(css))
+  })
+
+  it("errors if not list within list", {
+    css <- list(
+      ".class" = list(
+        list(color = "red"),
+        "font-size" = "30px"
+      ),
+      ".test" = list("red")
+    )
+    expect_error(list2css(css))
+  })
+})