Add custom heading adapter

Cargo.toml

@@ -10,7 +10,14 @@ readme = "README.md"
 keywords = ["markdown", "commonmark"]
 license = "BSD-2-Clause"
 categories = ["text-processing", "parsing", "command-line-utilities"]
-exclude = ["/hooks/*", "/script/*", "/vendor/*", "/.travis.yml", "/Makefile", "/spec_out.txt"]
+exclude = [
+    "/hooks/*",
+    "/script/*",
+    "/vendor/*",
+    "/.travis.yml",
+    "/Makefile",
+    "/spec_out.txt",
+]
 resolver = "2"
 
 [profile.release]
@@ -31,6 +38,7 @@ memchr = "2"
 pest = "2"
 pest_derive = "2"
 shell-words = { version = "1.0", optional = true }
+slug = "0.1.4"
 emojis = { version = "0.5.2", optional = true }
 
 [dev-dependencies]
@@ -48,9 +56,20 @@ shortcodes = ["emojis"]
 xdg = { version = "^2.1", optional = true }
 
 [target.'cfg(target_arch="wasm32")'.dependencies]
-syntect = { version = "5.0", optional = true, default-features = false, features = ["default-fancy"] }
+syntect = { version = "5.0", optional = true, default-features = false, features = [
+    "default-fancy",
+] }
 clap = { version = "4.0", optional = true, features = ["derive", "string"] }
 
 [target.'cfg(not(target_arch="wasm32"))'.dependencies]
-syntect = { version = "5.0", optional = true, default-features = false, features = ["default-themes", "default-syntaxes", "html", "regex-onig"] }
-clap = { version = "4.0", optional = true, features = ["derive", "string", "wrap_help"] }
+syntect = { version = "5.0", optional = true, default-features = false, features = [
+    "default-themes",
+    "default-syntaxes",
+    "html",
+    "regex-onig",
+] }
+clap = { version = "4.0", optional = true, features = [
+    "derive",
+    "string",
+    "wrap_help",
+] }

examples/custom_headings.rs

@@ -0,0 +1,51 @@
+extern crate comrak;
+extern crate slug;
+
+use comrak::{
+    adapters::{HeadingAdapter, HeadingMeta},
+    markdown_to_html_with_plugins, ComrakOptions, ComrakPlugins,
+};
+
+fn main() {
+    let adapter = CustomHeadingAdapter;
+    let options = ComrakOptions::default();
+    let mut plugins = ComrakPlugins::default();
+    plugins.render.heading_adapter = Some(&adapter);
+
+    print_html(
+        "Some text.\n\n## Please hide me from search\n\nSome other text",
+        &options,
+        &plugins,
+    );
+    print_html(
+        "Some text.\n\n### Here is some `code`\n\nSome other text",
+        &options,
+        &plugins,
+    );
+    print_html(
+        "Some text.\n\n### Here is some **bold** text and some *italicized* text\n\nSome other text",
+        &options,
+        &plugins
+    );
+    print_html("# Here is a [link](/)", &options, &plugins);
+}
+
+struct CustomHeadingAdapter;
+
+impl HeadingAdapter for CustomHeadingAdapter {
+    fn render(&self, heading: &HeadingMeta) -> String {
+        let id = slug::slugify(&heading.content);
+
+        let search_include = !&heading.content.contains("hide");
+
+        format!(
+            "<h{} id=\"{}\" data-search-include=\"{}\">",
+            heading.level, id, search_include
+        )
+    }
+}
+
+fn print_html(document: &str, options: &ComrakOptions, plugins: &ComrakPlugins) {
+    let html = markdown_to_html_with_plugins(document, options, plugins);
+    println!("{}", html);
+}

src/adapters.rs

@@ -24,3 +24,19 @@ pub trait SyntaxHighlighterAdapter {
     /// `attributes`: A map of HTML attributes provided by comrak.
     fn build_code_tag(&self, attributes: &HashMap<String, String>) -> String;
 }
+
+/// The struct passed to the `HeadingAdapter`.
+#[derive(Clone, Debug)]
+pub struct HeadingMeta {
+    /// The level of the header; from 1 to 6 for ATX headings, 1 or 2 for setext headings.
+    pub level: u32,
+
+    /// The text content of the heading.
+    pub content: String,
+}
+
+/// Implement this adapter for creating a plugin for custom headings.
+pub trait HeadingAdapter {
+    /// The rendering function for headings.
+    fn render(&self, heading: &HeadingMeta) -> String;
+}

src/html.rs

@@ -11,6 +11,8 @@ use std::io::{self, Write};
 use std::str;
 use strings::build_opening_tag;
 
+use crate::adapters::HeadingMeta;
+
 #[cfg(feature = "shortcodes")]
 extern crate emojis;
 
@@ -457,22 +459,40 @@ impl<'o> HtmlFormatter<'o> {
             }
             NodeValue::Heading(ref nch) => {
                 if entering {
-                    self.cr()?;
-                    write!(self.output, "<h{}>", nch.level)?;
-
-                    if let Some(ref prefix) = self.options.extension.header_ids {
-                        let mut text_content = Vec::with_capacity(20);
-                        self.collect_text(node, &mut text_content);
-
-                        let mut id = String::from_utf8(text_content).unwrap();
-                        id = self.anchorizer.anchorize(id);
-                        write!(
-                            self.output,
-                            "<a href=\"#{}\" aria-hidden=\"true\" class=\"anchor\" id=\"{}{}\"></a>",
-                            id,
-                            prefix,
-                            id
-                        )?;
+                    match self.plugins.render.heading_adapter {
+                        Some(adapter) => {
+                            let level = nch.level;
+                            let mut text_content = Vec::with_capacity(20);
+                            self.collect_text(node, &mut text_content);
+
+                            let content = &String::from_utf8(text_content).unwrap();
+
+                            let heading = HeadingMeta {
+                                level,
+                                content: String::from(content),
+                            };
+
+                            let rendered = adapter.render(&heading);
+                            write!(self.output, "{}", rendered)?;
+                        }
+                        None => {
+                            write!(self.output, "<h{}>", nch.level)?;
+
+                            if let Some(ref prefix) = self.options.extension.header_ids {
+                                let mut text_content = Vec::with_capacity(20);
+                                self.collect_text(node, &mut text_content);
+
+                                let mut id = String::from_utf8(text_content).unwrap();
+                                id = self.anchorizer.anchorize(id);
+                                write!(
+                                        self.output,
+                                        "<a href=\"#{}\" aria-hidden=\"true\" class=\"anchor\" id=\"{}{}\"></a>",
+                                        id,
+                                        prefix,
+                                        id
+                                    )?;
+                            }
+                        }
                     }
                 } else {
                     writeln!(self.output, "</h{}>", nch.level)?;

src/parser/mod.rs

@@ -25,6 +25,8 @@ use std::str;
 use strings;
 use typed_arena::Arena;
 
+use crate::adapters::HeadingAdapter;
+
 const TAB_STOP: usize = 4;
 const CODE_INDENT: usize = 4;
 
@@ -529,6 +531,9 @@ pub struct ComrakRenderPlugins<'a> {
     ///            "<pre lang=\"rust\"><code class=\"language-rust\"><span class=\"lang-rust\">fn main<'a>();\n</span></code></pre>\n");
     /// ```
     pub codefence_syntax_highlighter: Option<&'a dyn SyntaxHighlighterAdapter>,
+
+    /// Optional heading adapter
+    pub heading_adapter: Option<&'a dyn HeadingAdapter>,
 }
 
 impl Debug for ComrakRenderPlugins<'_> {

src/tests.rs

@@ -1398,6 +1398,7 @@ fn exercise_full_api<'a>() {
     let _ = ::ComrakPlugins {
         render: ::ComrakRenderPlugins {
             codefence_syntax_highlighter: Some(&syntax_highlighter_adapter),
+            heading_adapter: None,
         },
     };