align text in structured args

src/commonmark.rs

@@ -53,7 +53,7 @@ impl Argument {
                 format!(
                     "`{}`\n\n: {}\n\n",
                     arg.name,
-                    arg.doc.unwrap_or("Function argument".into()).trim()
+                    handle_indentation(arg.doc.unwrap_or("Function argument".into()).trim())
                 )
             }
 
@@ -85,6 +85,22 @@ impl Argument {
     }
 }
 
+/// Since the first line starts with `: `, indent every other line by 2 spaces, so
+/// that the text aligns, to result in:
+///
+/// : first line
+///   every other line
+fn handle_indentation(raw: &str) -> String {
+    let result: String = match raw.split_once('\n') {
+        Some((first, rest)) => {
+            format!("{}\n{}", first, textwrap::indent(rest, "  "))
+        }
+        None => raw.into(),
+    };
+
+    result
+}
+
 /// Represents a single manual section describing a library function.
 #[derive(Clone, Debug)]
 pub struct ManualEntry {

src/main.rs

@@ -503,3 +503,21 @@ fn test_line_comments() {
 
     insta::assert_snapshot!(output);
 }
+
+#[test]
+fn test_multi_line() {
+    let mut output = Vec::new();
+    let src = fs::read_to_string("test/multi-line.nix").unwrap();
+    let nix = rnix::Root::parse(&src).ok().expect("failed to parse input");
+    let category = "let";
+
+    for entry in collect_entries(nix, category) {
+        entry
+            .write_section(&Default::default(), &mut output)
+            .expect("Failed to write section")
+    }
+
+    let output = String::from_utf8(output).expect("not utf8");
+
+    insta::assert_snapshot!(output);
+}

src/snapshots/nixdoc__multi_line.snap

@@ -0,0 +1,31 @@
+---
+source: src/main.rs
+expression: output
+---
+## `lib.let.f` {#function-library-lib.let.f}
+
+Some description
+
+structured function argument
+
+: `x`
+
+  : First line
+
+    Second line
+
+
+## `lib.let.g` {#function-library-lib.let.g}
+
+Some other description
+
+structured function argument
+
+: `x`
+
+  : First line
+
+    Second line
+
+
+

test/multi-line.nix

@@ -0,0 +1,22 @@
+{
+  /* Some description */
+  f =
+    {
+      /* First line
+
+      Second line
+      */
+      x
+    }: x;
+
+  /* Some other description */
+  g =
+    {
+      /*
+      First line
+
+      Second line
+      */
+      x
+    }: x;
+}