Support multiline includes

crates/mdbook-driver/src/builtin_preprocessors/links.rs

@@ -97,17 +97,25 @@ where
         match link.render_with_path(path, chapter_title) {
             Ok(new_content) => {
                 if depth < MAX_LINK_NESTED_DEPTH {
-                    if let Some(rel_path) = link.link_type.relative_path(path) {
-                        replaced.push_str(&replace_all(
-                            &new_content,
-                            rel_path,
-                            source,
-                            depth + 1,
-                            chapter_title,
-                        ));
+                    // use split('\n') instead of lines because we DON'T
+                    // want the last \n to be removed
+                    // Otherwise includes starting a new line would be prefixed
+                    // by the preceding line
+                    let prefix = replaced.split('\n').last().unwrap_or("");
+                    let raw_new_content = if let Some(rel_path) = link.link_type.relative_path(path)
+                    {
+                        replace_all(&new_content, rel_path, source, depth + 1, chapter_title)
                     } else {
-                        replaced.push_str(&new_content);
-                    }
+                        new_content
+                    };
+                    // use lines instead of split('\n') because we DO
+                    // want the last \n to be removed
+                    // Otherwise inlined includes would fail
+                    let prefixed_new_content = raw_new_content
+                        .lines()
+                        .collect::<Vec<_>>()
+                        .join(&format!("\n{prefix}"));
+                    replaced.push_str(&prefixed_new_content);
                 } else {
                     error!(
                         "Stack depth exceeded in {}. Check for cyclic includes",

tests/testsuite/includes.rs

@@ -24,6 +24,28 @@ fn include() {
         );
 }
 
+// Basic test for #include.
+#[test]
+fn include_multilines() {
+    BookTest::from_dir("includes/all_includes").check_main_file(
+        "book/multilines.html",
+        str![[r##"
+<h1 id="multilines-include"><a class="header" href="#multilines-include">Multilines include</a></h1>
+<p>Simple inclusion</p>
+<pre><pre class="playground"><code class="language-rust">pub fn main() {
+    println!("Hello, World")
+}</code></pre></pre>
+<blockquote>
+<p>Quoted inclusion</p>
+<pre><pre class="playground"><code class="language-rust">pub fn main() {
+    println!("Hello, World")
+}</code></pre></pre>
+</blockquote>
+<p>end</p>
+"##]],
+    );
+}
+
 // Checks for anchored includes.
 #[test]
 fn anchored_include() {

tests/testsuite/includes/all_includes/src/SUMMARY.md

@@ -6,3 +6,4 @@
 - [Include Anchors](./anchors.md)
 - [Rustdoc Includes](./rustdoc.md)
 - [Playground Includes](./playground.md)
+- [Multilines Includes](./multilines.md)

tests/testsuite/includes/all_includes/src/hello_world.rs

@@ -0,0 +1,3 @@
+pub fn main() {
+    println!("Hello, World")
+}

tests/testsuite/includes/all_includes/src/multilines.md

@@ -0,0 +1,14 @@
+# Multilines include
+
+Simple inclusion
+
+```rust
+{{#include hello_world.rs}}
+```
+
+> Quoted inclusion
+> ```rust
+> {{#include hello_world.rs}}
+> ```
+
+end