Add some external link markdown tweaking options

Closes #681, #695

CHANGELOG.md

@@ -6,12 +6,13 @@
 - Support `output_dir` in `config.toml`
 - Allow sections to be drafted
 - Allow specifying default language in filenames
-- Render emoji in Markdown content if the option is enabled
+- Render emoji in Markdown content if the `render_emoji` option is enabled
 - Enable YouTube privacy mode for the YouTube shortcode
 - Add language as class to the `<code>` block
 - Add bibtex to `load_data`
 - Add a `[markdown]` section to `config.toml` to configure rendering
 - Add `highlight_code` and `highlight_theme` to a `[markdown]` section in `config.toml`
+- Add `external_links_target_blank`, `external_links_no_follow` and `external_links_no_referrer`
 
 ## 0.12.2 (2020-09-28)
 

components/config/src/config/markup.rs

@@ -12,6 +12,46 @@ pub struct Markdown {
     pub highlight_theme: String,
     /// Whether to render emoji aliases (e.g.: :smile: => 😄) in the markdown files
     pub render_emoji: bool,
+    /// Whether external links are to be opened in a new tab
+    /// If this is true, a `rel="noopener"` will always automatically be added for security reasons
+    pub external_links_target_blank: bool,
+    /// Whether to set rel="nofollow" for all external links
+    pub external_links_no_follow: bool,
+    /// Whether to set rel="noreferrer" for all external links
+    pub external_links_no_referrer: bool,
+}
+
+impl Markdown {
+    pub fn has_external_link_tweaks(&self) -> bool {
+        self.external_links_target_blank
+            || self.external_links_no_follow
+            || self.external_links_no_referrer
+    }
+
+    pub fn construct_external_link_tag(&self, url: &str, title: &str) -> String {
+        let mut rel_opts = Vec::new();
+        let mut target = "".to_owned();
+        let title = if title == "" { "".to_owned() } else { format!("title=\"{}\" ", title) };
+
+        if self.external_links_target_blank {
+            // Security risk otherwise
+            rel_opts.push("noopener");
+            target = "target=\"_blank\" ".to_owned();
+        }
+        if self.external_links_no_follow {
+            rel_opts.push("nofollow");
+        }
+        if self.external_links_no_referrer {
+            rel_opts.push("noreferrer");
+        }
+        let rel = if rel_opts.is_empty() {
+            "".to_owned()
+        } else {
+            format!("rel=\"{}\" ", rel_opts.join(" "))
+        };
+
+        format!("<a {}{}{}href=\"{}\">", rel, target, title, url)
+    }
 }
 
 impl Default for Markdown {
@@ -20,6 +60,9 @@ impl Default for Markdown {
             highlight_code: false,
             highlight_theme: DEFAULT_HIGHLIGHT_THEME.to_owned(),
             render_emoji: false,
+            external_links_target_blank: false,
+            external_links_no_follow: false,
+            external_links_no_referrer: false,
         }
     }
 }

components/rendering/src/markdown.rs

@@ -13,7 +13,6 @@ use utils::slugs::slugify_anchors;
 use utils::vec::InsertMany;
 
 use self::cmark::{Event, LinkType, Options, Parser, Tag};
-use pulldown_cmark::CodeBlockKind;
 
 mod codeblock;
 mod fence;
@@ -101,11 +100,6 @@ fn fix_link(
         return Ok(link.to_string());
     }
 
-    // TODO: remove me in a few versions when people have upgraded
-    if link.starts_with("./") && link.contains(".md") {
-        println!("It looks like the link `{}` is using the previous syntax for internal links: start with @/ instead", link);
-    }
-
     // A few situations here:
     // - it could be a relative link (starting with `@/`)
     // - it could be a link to a co-located asset
@@ -211,7 +205,7 @@ pub fn markdown_to_html(content: &str, context: &RenderContext) -> Result<Render
                     }
                     Event::Start(Tag::CodeBlock(ref kind)) => {
                         let language = match kind {
-                            CodeBlockKind::Fenced(fence_info) => {
+                            cmark::CodeBlockKind::Fenced(fence_info) => {
                                 let fence_info = fence::FenceSettings::new(fence_info);
                                 fence_info.language
                             }
@@ -228,8 +222,8 @@ pub fn markdown_to_html(content: &str, context: &RenderContext) -> Result<Render
 
                         let theme = &THEME_SET.themes[context.config.highlight_theme()];
                         match kind {
-                            CodeBlockKind::Indented => (),
-                            CodeBlockKind::Fenced(fence_info) => {
+                            cmark::CodeBlockKind::Indented => (),
+                            cmark::CodeBlockKind::Fenced(fence_info) => {
                                 // This selects the background color the same way that
                                 // start_coloured_html_snippet does
                                 let color = theme
@@ -289,8 +283,22 @@ pub fn markdown_to_html(content: &str, context: &RenderContext) -> Result<Render
                                 return Event::Html("".into());
                             }
                         };
-
-                        Event::Start(Tag::Link(link_type, fixed_link.into(), title))
+                        if is_external_link(&link)
+                            && context.config.markdown.has_external_link_tweaks()
+                        {
+                            let mut escaped = String::new();
+                            // write_str can fail but here there are no reasons it should (afaik?)
+                            cmark::escape::escape_href(&mut escaped, &link).expect("Could not write to buffer");
+                            Event::Html(
+                                context
+                                    .config
+                                    .markdown
+                                    .construct_external_link_tag(&escaped, &title)
+                                    .into(),
+                            )
+                        } else {
+                            Event::Start(Tag::Link(link_type, fixed_link.into(), title))
+                        }
                     }
                     Event::Html(ref markup) => {
                         if markup.contains("<!-- more -->") {

components/rendering/tests/markdown.rs

@@ -1058,3 +1058,61 @@ fn emoji_aliases_are_ignored_when_disabled_in_config() {
     let res = render_content("Hello, World! :smile:", &context).unwrap();
     assert_eq!(res.body, "<p>Hello, World! :smile:</p>\n");
 }
+
+#[test]
+fn basic_external_links_unchanged() {
+    let permalinks_ctx = HashMap::new();
+    let config = Config::default();
+    let context = RenderContext::new(&ZOLA_TERA, &config, "", &permalinks_ctx, InsertAnchor::None);
+    let res = render_content("<https://google.com>", &context).unwrap();
+    assert_eq!(res.body, "<p><a href=\"https://google.com\">https://google.com</a></p>\n");
+}
+
+#[test]
+fn can_set_target_blank_for_external_link() {
+    let permalinks_ctx = HashMap::new();
+    let mut config = Config::default();
+    config.markdown.external_links_target_blank = true;
+    let context = RenderContext::new(&ZOLA_TERA, &config, "", &permalinks_ctx, InsertAnchor::None);
+    let res = render_content("<https://google.com>", &context).unwrap();
+    assert_eq!(res.body, "<p><a rel=\"noopener\" target=\"_blank\" href=\"https://google.com\">https://google.com</a></p>\n");
+}
+
+#[test]
+fn can_set_nofollow_for_external_link() {
+    let permalinks_ctx = HashMap::new();
+    let mut config = Config::default();
+    config.markdown.external_links_no_follow = true;
+    let context = RenderContext::new(&ZOLA_TERA, &config, "", &permalinks_ctx, InsertAnchor::None);
+    // Testing href escaping while we're there
+    let res = render_content("<https://google.com/éllo>", &context).unwrap();
+    assert_eq!(
+        res.body,
+        "<p><a rel=\"nofollow\" href=\"https://google.com/%C3%A9llo\">https://google.com/éllo</a></p>\n"
+    );
+}
+
+#[test]
+fn can_set_noreferrer_for_external_link() {
+    let permalinks_ctx = HashMap::new();
+    let mut config = Config::default();
+    config.markdown.external_links_no_referrer = true;
+    let context = RenderContext::new(&ZOLA_TERA, &config, "", &permalinks_ctx, InsertAnchor::None);
+    let res = render_content("<https://google.com>", &context).unwrap();
+    assert_eq!(
+        res.body,
+        "<p><a rel=\"noreferrer\" href=\"https://google.com\">https://google.com</a></p>\n"
+    );
+}
+
+#[test]
+fn can_set_all_options_for_external_link() {
+    let permalinks_ctx = HashMap::new();
+    let mut config = Config::default();
+    config.markdown.external_links_target_blank = true;
+    config.markdown.external_links_no_follow = true;
+    config.markdown.external_links_no_referrer = true;
+    let context = RenderContext::new(&ZOLA_TERA, &config, "", &permalinks_ctx, InsertAnchor::None);
+    let res = render_content("<https://google.com>", &context).unwrap();
+    assert_eq!(res.body, "<p><a rel=\"noopener nofollow noreferrer\" target=\"_blank\" href=\"https://google.com\">https://google.com</a></p>\n");
+}

docs/content/documentation/getting-started/configuration.md

@@ -95,6 +95,7 @@ extra_syntaxes = []
 # You can override the default output directory `public` by setting an another value.
 # output_dir = "docs"
 
+# Configuration of the Markdown rendering
 [markdown]
 # When set to "true", all code blocks are highlighted.
 highlight_code = false
@@ -107,6 +108,16 @@ highlight_theme = "base16-ocean-dark"
 # Unicode emoji equivalent in the rendered Markdown files. (e.g.: :smile: => 😄)
 render_emoji = false
 
+# Whether external links are to be opened in a new tab
+# If this is true, a `rel="noopener"` will always automatically be added for security reasons
+external_links_target_blank = false
+
+# Whether to set rel="nofollow" for all external links
+external_links_no_follow = false
+
+# Whether to set rel="noreferrer" for all external links
+external_links_no_referrer = false
+
 # Configuration of the link checker.
 [link_checker]
 # Skip link checking for external URLs that start with these prefixes