Check that articles include alt-text for all images

Need to merge after #2518 (since the vignette will need a small update) and #2516 (since `check_built()` has moved).

Fixes #2357

NEWS.md

@@ -1,5 +1,6 @@
 # pkgdown (development version)
 
+* `build_articles()` now reports if you are missing alt-text for any images (#2357).
 * `build_reference()` now supports `\Sexpr[results=verbatim]` (@bastistician, #2510).
 * `build_home()` no longer checks if the README is missing any images. This check is now performed in `build_site()`, after `build_articles()` so you can refer to images created by vignettes with warnings (#2194).
 * `build_home()` now includes the contents of `inst/AUTHORS` on the authors page (#2506).

R/check.R

@@ -34,17 +34,27 @@ check_built_site <- function(pkg = ".") {
 
 check_missing_images <- function(pkg, src_path, dst_path) {
   html <- xml2::read_html(path(pkg$dst_path, dst_path), encoding = "UTF-8")
-  src <- xml2::xml_attr(xml2::xml_find_all(html, ".//img"), "src")
+  img <- xml2::xml_find_all(html, ".//img")
 
+  src <- xml2::xml_attr(img, "src")
   rel_src <- src[xml2::url_parse(src)$scheme == ""]
   rel_path <- fs::path_norm(path(fs::path_dir(dst_path), rel_src))
   exists <- fs::file_exists(path(pkg$dst_path, rel_path))
-
   if (any(!exists)) {
     paths <- rel_src[!exists]
-    cli::cli_warn(c(
-      "Missing images in {.file {path_rel(src_path, pkg$src_path)}}: {.file {paths}}",
+    cli::cli_inform(c(
+      x = "Missing images in {.file {path_rel(src_path, pkg$src_path)}}: {.file {paths}}",
       i = "pkgdown can only use images in {.file man/figures} and {.file vignettes}"
     ))
   }
+
+  alt <- xml2::xml_attr(img, "alt")
+  if (any(is.na(alt))) {
+    problems <- src[is.na(alt)]
+    problems[grepl("^data:image", problems)] <- "<base64 encoded image"
+    cli::cli_inform(c(
+      x = "Missing alt-text in {.file {path_rel(src_path, pkg$src_path)}}",
+      set_names(problems, "*")
+    ))
+  }
 }

tests/testthat/_snaps/build-articles.md

@@ -7,11 +7,20 @@
       Writing `articles/index.html`
       Reading vignettes/html-vignette.Rmd
       Writing `articles/html-vignette.html`
-    Condition
-      Warning:
-      Missing images in 'vignettes/html-vignette.Rmd': 'kitten.jpg'
+      x Missing images in 'vignettes/html-vignette.Rmd': 'kitten.jpg'
       i pkgdown can only use images in 'man/figures' and 'vignettes'
 
+# warns about missing alt-text
+
+    Code
+      build_article("missing-images", pkg)
+    Message
+      Reading vignettes/missing-images.Rmd
+      Writing `articles/missing-images.html`
+      x Missing alt-text in 'vignettes/missing-images.Rmd'
+      * kitten.jpg
+      * missing-images_files/figure-html/unnamed-chunk-1-1.png
+
 # articles don't include header-attrs.js script
 
     Code

tests/testthat/_snaps/check.md

@@ -30,8 +30,6 @@
       check_built_site(pkg)
     Message
       -- Checking for problems -------------------------------------------------------
-    Condition
-      Warning:
-      Missing images in 'README.md': 'articles/kitten.jpg'
+      x Missing images in 'README.md': 'articles/kitten.jpg'
       i pkgdown can only use images in 'man/figures' and 'vignettes'
 

tests/testthat/assets/bad-images/README.md

@@ -1,2 +1,2 @@
 
-![](vignettes/kitten.jpg)
+![picture of a cute kitten](vignettes/kitten.jpg)

tests/testthat/assets/bad-images/vignettes/html-vignette.Rmd

@@ -6,4 +6,4 @@ title: "test"
 knitr::opts_chunk$set(collapse = TRUE, comment = "#>")
 ```
 
-![](kitten.jpg)
+![picture of a cute kitten](kitten.jpg)

tests/testthat/assets/figure/vignettes/figures.Rmd

@@ -3,5 +3,6 @@ title: "Test: Figures"
 ---
 
 ```{r}
+#| fig-alt: A scatterplot of the numbers 1-10.
 plot(1:10)
 ```

tests/testthat/assets/missing-alt/DESCRIPTION

@@ -0,0 +1,9 @@
+Package: testpackage
+Version: 1.0.0
+Title: A test package
+Description: A longer statement about the package.
+Authors@R: c(
+    person("Hadley", "Wickham", , "[email protected]", role = c("aut", "cre")),
+    person("RStudio", role = c("cph", "fnd"))
+    )
+RoxygenNote: 6.0.1

tests/testthat/assets/missing-alt/vignettes/missing-images.Rmd

@@ -0,0 +1,10 @@
+---
+title: "test"
+---
+
+![](kitten.jpg)
+
+
+```{r}
+plot(1:5)
+```

tests/testthat/assets/vignette-with-img.Rmd

@@ -12,5 +12,6 @@ vignette: >
 Some words, and then an image like this:
 
 ```{r, echo = FALSE}
+#| fig-alt: The pkgdown logo
 knitr::include_graphics("open-graph/logo.png")
 ```

tests/testthat/test-build-articles.R

@@ -41,6 +41,11 @@ test_that("warns about missing images", {
   expect_snapshot(build_articles(pkg))
 })
 
+test_that("warns about missing alt-text", {
+  pkg <- local_pkgdown_site(test_path("assets/missing-alt"))
+  expect_snapshot(build_article("missing-images", pkg))
+})
+
 test_that("articles don't include header-attrs.js script", {
   pkg <- as_pkgdown(test_path("assets/articles"))
   withr::defer(clean_site(pkg, quiet = TRUE))