Make Hugo's LiveReload work on RStudio Server

DESCRIPTION

@@ -1,7 +1,7 @@
 Type: Package
 Package: blogdown
 Title: Create Blogs and Websites with R Markdown
-Version: 1.13.2
+Version: 1.13.4
 Authors@R: c(
     person("Yihui", "Xie", role = c("aut", "cre"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666")),
     person("Christophe", "Dervieux", role = "aut", email = "[email protected]", comment = c(ORCID = "0000-0003-4474-2498")),
@@ -67,3 +67,4 @@ Config/Needs/website: pkgdown, tidyverse/tidytemplate, rstudio/quillt, rstudio/w
 Encoding: UTF-8
 RoxygenNote: 7.2.1
 SystemRequirements: Hugo (<https://gohugo.io>) and Pandoc (<https://pandoc.org>)
+Remotes: yihui/servr

NEWS.md

@@ -1,5 +1,7 @@
 # CHANGES IN blogdown VERSION 1.14
 
+- `blogdown::serve_site()` works fully on RStudio server now. Previously, Hugo's LiveReload and absolute URLs on pages did not work. Both problems have been fixed. The former issue requires the Hugo version to be equal to or greater than `0.80.0`.
+
 - When rendering Rmd posts that involve time-consuming and intensive computing while serving the site, the `hugo` process can die (for unknown reasons). Now the `hugo` process will be suspended before rendering Rmd posts, and resumed after the rendering is done. Hopefully this will keep the server process alive (thanks, @XiangyunHuang, https://d.cosx.org/d/423509).
 
 # CHANGES IN blogdown VERSION 1.13

R/serve.R

@@ -55,9 +55,11 @@ serve_site = function(..., .site_dir = NULL) {
   serve(..., .site_dir = .site_dir)
 }
 
-server_ready = function(url) {
+server_ready = function(url, base = NULL) {
   # for some reason, R cannot read localhost, but 127.0.0.1 works
   url = sub('^http://localhost:', 'http://127.0.0.1:', url)
+  # need to include a subpath from RStudio translation
+  if (!is.null(base)) url = paste0(url, '/', rstudioapi::translateLocalUrl(base))
   !inherits(
     xfun::try_silent(suppressWarnings(readLines(url))), 'try-error'
   )
@@ -111,10 +113,20 @@ serve_it = function(pdir = publish_dir(), baseurl = site_base_dir()) {
 
     owd = setwd(root); on.exit(setwd(owd), add = TRUE)
 
+    rsv = is_rstudio_server()
+    if (rsv) baseurl = ''  # don't use baseurl on RStudio Server
+
     server = servr::server_config(..., baseurl = baseurl, hosturl = function(host) {
       if (g == 'hugo' && host == '127.0.0.1') 'localhost' else host
     })
 
+    if (rsv) {
+      port2 = servr::random_port(exclude = server$port)
+      server2 = servr::create_server(
+        port = port2, browser = FALSE, handler = proxy_handler(server$port, port2)
+      )
+    }
+
     # launch the hugo/jekyll/hexo server
     cmd = if (g == 'hugo') find_hugo() else g
     host = server$host; port = server$port; intv = server$interval
@@ -127,7 +139,10 @@ serve_it = function(pdir = publish_dir(), baseurl = site_base_dir()) {
       # RStudio Server uses a proxy like http://localhost:8787/p/56a946ed/ for
       # http://localhost:4321, so we must use relativeURLs = TRUE:
       # https://github.com/rstudio/blogdown/issues/124
-      tweak_hugo_env(server = TRUE, relativeURLs = if (is_rstudio_server()) TRUE)
+      tweak_hugo_env(
+        baseURL = if (rsv) rstudioapi::translateLocalUrl(server2$url, TRUE),
+        relativeURLs = if (rsv) TRUE, server = TRUE
+      )
       if (length(list_rmds(pattern = bundle_regex('.R(md|markdown)$'))))
         create_shortcode('postref.html', 'blogdown/postref')
     }
@@ -174,7 +189,7 @@ serve_it = function(pdir = publish_dir(), baseurl = site_base_dir()) {
           'Failed to serve the site; see if blogdown::build_site() gives more info.'
         } else err, call. = FALSE)
       }
-      if (server_ready(server$url)) break
+      if (server_ready(server$url, if (rsv) server2$url)) break
       if (i >= get_option('blogdown.server.timeout', 30)) {
         s = proc_kill(pid)  # if s == 0, the server must have been started successfully
         stop(if (s == 0) c(
@@ -189,7 +204,7 @@ serve_it = function(pdir = publish_dir(), baseurl = site_base_dir()) {
       }
       i = i + 1
     }
-    server$browse()
+    if (rsv) server2$browse(TRUE) else server$browse()
     # server is correctly started so we record the directory served
     opts$append(served_dirs = root)
     Sys.setenv(BLOGDOWN_SERVING_DIR = root)
@@ -287,14 +302,54 @@ get_config2 = function(key, default) {
 }
 
 # refresh the viewer because hugo's livereload doesn't work on RStudio
-# Server: https://github.com/rstudio/rstudio/issues/8096 (TODO: check if
-# it's fixed in the future: https://github.com/gohugoio/hugo/pull/6698)
+# Server: https://github.com/rstudio/rstudio/issues/8096
 refresh_viewer = function() {
-  if (!is_rstudio_server()) return()
+  # Hugo 0.80.0 has fixed this issue: https://github.com/gohugoio/hugo/pull/6698
+  if (!is_rstudio_server() || hugo_available('0.80.0')) return()
   server_wait()
   rstudioapi::executeCommand('viewerRefresh')
 }
 
 server_wait = function() {
   Sys.sleep(get_option('blogdown.server.wait', 2))
 }
+
+# port is hugo's port; port2 is servr proxy's port
+proxy_handler = function(port, port2) {
+  # hugo and proxy's base urls
+  b1 = rstudioapi::translateLocalUrl(sprintf('http://localhost:%d', port))
+  b2 = rstudioapi::translateLocalUrl(sprintf('http://localhost:%d', port2))
+  function(req) {
+    path = req$PATH_INFO
+    # add proxy's base url and remove redundant base urls if absent
+    path = gsub(sprintf('^/(%s)*', b2), b2, path, perl = TRUE)
+    path = paste0('/', path)
+    u = sprintf('http://127.0.0.1:%d%s', port, path)
+    # for HTML pages, read their content; for other resources, redirect to hugo
+    if (grepl('[.]html?|/$', path)) {
+      fix_livereload(proxy_response(u), b1, b2)
+    } else {
+      servr::redirect(rstudioapi::translateLocalUrl(u, TRUE))
+    }
+  }
+}
+
+proxy_response = function(url, status = 200L, type = mime::guess_type(url, empty = 'text/html')) {
+  tryCatch(list(
+    status = status, headers = list('Content-Type' = type),
+    body = paste(readLines(url, encoding = 'UTF-8', warn = FALSE), collapse = '\n')
+  ), error = function(e) list(
+    status = 404L, headers = list('Content-Type' = 'text/plain'),
+    body = paste('Not found:', url)
+  ))
+}
+
+# fix the location of hugo's livereload.js: re-route from the proxy to hugo
+# (unfortunately RStudio Server seems to interfere with loading livereload.js;
+# all other assets can be loaded correctly, but I don't know why livereload.js
+# is an exception)
+fix_livereload = function(res, b1, b2) {
+  if (!identical(res$headers[['Content-Type']], 'text/html')) return(res)
+  res$body = gsub(sprintf('(src="/)(%slivereload[.]js)', b2), sprintf('\\1%s\\2', b1), res$body)
+  res
+}

R/utils.R

@@ -955,7 +955,7 @@ tweak_hugo_env = function(baseURL = NULL, relativeURLs = NULL, server = FALSE) {
   c2 = if (is.null(relativeURLs)) get_config('relativeurls', FALSE, config) else relativeURLs
   if (server && c1) b = paste0(if (grepl('^//', b)) 'http:' else 'http://example.org/', b)
 
-  vars = c(HUGO_BASEURL = if (c2) '/' else b, HUGO_RELATIVEURLS = tolower(c2))
+  vars = c(HUGO_BASEURL = if (c2 && !server) '/' else b, HUGO_RELATIVEURLS = tolower(c2))
   if (server) {
     vars = c(vars, HUGO_BLOGDOWN_POST_RELREF = 'true')
     c3 = get_config('ignoreErrors', NA, config)