Add support for "external" articles

NEWS.md

@@ -1,5 +1,6 @@
 # pkgdown (development version)
 
+* `build_articles()` now recognises a new `external-articles` top-level field that allows you to define articles that live in other packages (#2028).
 * `vignette("search")` has been removed since BS3 is deprecated and all the BS5 docs are also included in `build_search()` (#2564).
 * YAML validation has been substantially improved so you should get much clearer errors if you have made a mistake (#1927). Please file an issue if you find a case where the error message is not helpful.
 * `template_reference()` and `template_article()` now only add backticks to function names if needed (#2561).

R/build-articles.R

@@ -77,7 +77,7 @@
 #' the navbar, it will link directly to the articles index instead of
 #' providing a drop-down.
 #'
-#' # Get started
+#' ## Get started
 #' Note that a vignette with the same name as the package (e.g.,
 #' `vignettes/pkgdown.Rmd` or `vignettes/articles/pkgdown.Rmd`) automatically
 #' becomes a top-level "Get started" link, and will not appear in the articles
@@ -86,13 +86,27 @@
 #' (If your package name includes a `.`, e.g. `pack.down`, use a `-` in the
 #' vignette name, e.g. `pack-down.Rmd`.)
 #'
-#' ## Missing topics
+#' ## Missing articles
 #'
 #' pkgdown will warn if there are (non-internal) articles that aren't listed
 #' in the articles index. You can suppress such warnings by listing the
 #' affected articles in a section with `title: internal` (case sensitive);
 #' this section will not be displayed on the index page.
+#' 
+#' ## External articles
 #'
+#' You can link to arbitrary additional articles by adding an 
+#' `external-articles` entry to `_pkgdown.yml`. It should contain an array
+#' of objects with fields `name`, `title`, `href`, and `description`. 
+#'
+#' ```yaml
+#' external-articles:
+#' - name: subsampling
+#'   title: Subsampling for Class Imbalances
+#'   description: Improve model performance in imbalanced data sets through undersampling or oversampling.
+#'   href: https://www.tidymodels.org/learn/models/sub-sampling/
+#' ```
+#' 
 #' # External files
 #' pkgdown differs from base R in its handling of external files. When building
 #' vignettes, R assumes that vignettes are self-contained (a reasonable
@@ -378,16 +392,16 @@ build_articles_index <- function(pkg = ".") {
 data_articles_index <- function(pkg = ".", call = caller_env()) {
   pkg <- as_pkgdown(pkg)
 
-  meta <- config_pluck_list(
-    pkg,
-    "articles",
-    default = default_articles_index(pkg),
+  articles <- data_articles(pkg, is_index = TRUE, call = call)
+  index <- config_pluck_list(pkg, "articles", call = call) %||%
+    default_articles_index(pkg)
+  sections <- unwrap_purrr_error(purrr::imap(
+    index,
+    data_articles_index_section,
+    articles = articles,
+    pkg = pkg,
     call = call
-  )
-
-  sections <- unwrap_purrr_error(meta %>%
-    purrr::imap(data_articles_index_section, pkg = pkg, call = call) %>%
-    purrr::compact())
+  ))
 
   # Check for unlisted vignettes
   listed <- sections %>%
@@ -396,7 +410,7 @@ data_articles_index <- function(pkg = ".", call = caller_env()) {
     purrr::flatten_chr() %>%
     unique()
 
-  missing <- setdiff(pkg$vignettes$name, listed)
+  missing <- setdiff(articles$name, listed)
   # Exclude get started vignette or article #2150
   missing <- missing[!article_is_intro(missing, package = pkg$package)]
 
@@ -417,10 +431,89 @@ data_articles_index <- function(pkg = ".", call = caller_env()) {
   ))
 }
 
-data_articles_index_section <- function(section, index, pkg, call = caller_env()) {
+data_articles <- function(pkg = ".", is_index = FALSE, call = caller_env()) {
+  pkg <- as_pkgdown(pkg)
+
+  internal <- tibble::tibble(
+    name = pkg$vignettes$name,
+    title = pkg$vignettes$title,
+    href = pkg$vignettes$file_out,
+    description = pkg$vignettes$description,
+  )
+  if (is_index) {
+    internal$href <- path_rel(internal$href, "articles")
+  }
+
+  external <- config_pluck_external_articles(pkg, call = call)
+  articles <- rbind(internal, external)
+
+  articles$description <- lapply(articles$description, markdown_text_block)
+
+  # Hack data structure so we can use select_topics()
+  articles$alias <- as.list(articles$name)
+  articles$internal <- FALSE
+
+  articles
+}
+
+config_pluck_external_articles <- function(pkg, call = caller_env()) {
+  external <- config_pluck_list(pkg, "external-articles", call = call)
+  if (is.null(external)) {
+    return(tibble::tibble(
+      name = character(),
+      title = character(),
+      href = character(),
+      description = character()
+    ))
+  }
+
+  for (i in seq_along(external)) {
+    config_check_list(
+      external[[i]],
+      has_names = c("name", "title", "href", "description"),
+      error_path = paste0("external-articles[", i, "]"),
+      error_pkg = pkg,
+      error_call = call
+    )
+    config_check_string(
+      external[[i]]$name,
+      error_path = paste0("external-articles[", i, "].name"),
+      error_pkg = pkg,
+      error_call = call
+    )
+    config_check_string(
+      external[[i]]$title,
+      error_path = paste0("external-articles[", i, "].title"),
+      error_pkg = pkg,
+      error_call = call
+    )
+    config_check_string(
+      external[[i]]$href,
+      error_path = paste0("external-articles[", i, "].href"),
+      error_pkg = pkg,
+      error_call = call
+    )
+    config_check_string(
+      external[[i]]$description,
+      error_path = paste0("external-articles[", i, "].description"),
+      error_pkg = pkg,
+      error_call = call
+    )
+  }
+
+  tibble::tibble(
+    name = purrr::map_chr(external, "name"),
+    title = purrr::map_chr(external, "title"),
+    href = purrr::map_chr(external, "href"),
+    description = purrr::map_chr(external, "description")
+  )
+}
+
+data_articles_index_section <- function(section, index, articles, pkg, call = caller_env()) {
   config_check_list(
     section,
     error_path = paste0("articles[", index, "]"),
+    has_names = c("title", "contents"),
     error_pkg = pkg,
     error_call = call
   )
@@ -443,24 +536,10 @@ data_articles_index_section <- function(section, index, pkg, call = caller_env()
     error_pkg = pkg,
     error_call = call
   )
-  check_contents(
-    section$contents,
-    index,
-    pkg,
-    prefix = "articles",
-    quote(build_articles())
-  )
+  check_contents(section$contents, index, pkg, prefix = "articles", call = call)
 
   # Match topics against any aliases
-  in_section <- select_vignettes(section$contents, pkg$vignettes)
-  section_vignettes <- pkg$vignettes[in_section, ]
-  contents <- tibble::tibble(
-    name = section_vignettes$name,
-    path = path_rel(section_vignettes$file_out, "articles"),
-    title = section_vignettes$title,
-    description = lapply(section_vignettes$description, markdown_text_block),
-  )
-
+  contents <- articles[select_topics(section$contents, articles), ]
 
   list(
     title = title,
@@ -470,17 +549,6 @@ data_articles_index_section <- function(section, index, pkg, call = caller_env()
   )
 }
 
-# Quick hack: create the same structure as for topics so we can use
-# the existing select_topics()
-select_vignettes <- function(match_strings, vignettes) {
-  topics <- tibble::tibble(
-    name = vignettes$name,
-    alias = as.list(vignettes$name),
-    internal = FALSE
-  )
-  select_topics(match_strings, topics)
-}
-
 default_articles_index <- function(pkg = ".") {
   pkg <- as_pkgdown(pkg)
 

R/navbar.R

@@ -165,24 +165,25 @@ navbar_articles <- function(pkg = ".") {
       menu_links(vignettes$title, vignettes$file_out)
     )
   } else {
-    articles <- config_pluck(pkg, "articles")
+    articles_index <- config_pluck(pkg, "articles")
+    articles <- data_articles(pkg)
 
-    navbar <- purrr::keep(articles, ~ has_name(.x, "navbar"))
+    navbar <- purrr::keep(articles_index, ~ has_name(.x, "navbar"))
     if (length(navbar) == 0) {
       # No articles to be included in navbar so just link to index
       menu$articles <- menu_link(tr_("Articles"), "articles/index.html")
     } else {
       sections <- lapply(navbar, function(section) {
-        vig <- pkg$vignettes[select_vignettes(section$contents, pkg$vignettes), , drop = FALSE]
+        vig <- articles[select_topics(section$contents, articles), , drop = FALSE]
         vig <- vig[vig$name != pkg$package, , drop = FALSE]
         c(
           if (!is.null(section$navbar)) list(menu_separator(), menu_heading(section$navbar)),
-          menu_links(vig$title, vig$file_out)
+          menu_links(vig$title, vig$href)
         )
       })
       children <- unlist(sections, recursive = FALSE, use.names = FALSE)
 
-      if (length(navbar) != length(articles)) {
+      if (length(navbar) != length(articles_index)) {
         children <- c(
           children,
           list(
@@ -221,7 +222,7 @@ pkg_navbar_vignettes <- function(name = character(),
   title <- title %||% paste0("Title ", name)
   file_out <- file_out %||% paste0(name, ".html")
 
-  tibble::tibble(name = name, title = title, file_out)
+  tibble::tibble(name = name, title = title, file_out, description = "desc")
 }
 
 

R/package.R

@@ -316,7 +316,7 @@ package_vignettes <- function(path = ".") {
   check_unique_article_paths(file_in, file_out)
 
   out <- tibble::tibble(
-    name = path_ext_remove(vig_path),
+    name = as.character(path_ext_remove(vig_path)),
     file_in = file_in,
     file_out = file_out,
     title = title,

inst/BS3/templates/content-article-index.html

@@ -11,7 +11,7 @@ <h3>{{{title}}}</h3>
 
       <dl>
         {{#contents}}
-        <dt><a href="{{path}}">{{title}}</a></dt>
+        <dt><a href="{{href}}">{{title}}</a></dt>
         <dd>{{{description}}}</dt>
         {{/contents}}
       </dl>

inst/BS5/templates/content-article-index.html

@@ -12,7 +12,7 @@ <h3>{{{title}}}</h3>
 
       <dl>
         {{#contents}}
-        <dt><a href="{{path}}">{{title}}</a></dt>
+        <dt><a href="{{href}}">{{title}}</a></dt>
         <dd>{{{description}}}</dt>
         {{/contents}}
       </dl>