feat: add listIndentKind config option (#176)

Author: jamestrousdale

Cargo.lock

@@ -84,6 +84,18 @@
         "description": "Uses an underline of = or - beneath the heading text (setext headings). Only applies to level 1 and 2 headings."
       }]
     },
+    "listIndentKind": {
+      "description": "The style of indentation to use for list items. CommonMark aligns to the content column after the marker. PythonMarkdown uses a fixed 4-space indent, required by tools like mkdocs-material.",
+      "type": "string",
+      "default": "commonMark",
+      "oneOf": [{
+        "const": "commonMark",
+        "description": "Indents continuation lines to align with the content after the list marker (e.g. 3 spaces for '1. ', 4 for '10. ')."
+      }, {
+        "const": "pythonMarkdown",
+        "description": "Always indents by 4 spaces, regardless of marker width."
+      }]
+    },
     "deno": {
       "description": "Top level configuration that sets the configuration to what is used in Deno.",
       "type": "boolean",
@@ -125,6 +137,9 @@
     "headingKind": {
       "$ref": "#/definitions/headingKind"
     },
+    "listIndentKind": {
+      "$ref": "#/definitions/listIndentKind"
+    },
     "deno": {
       "$ref": "#/definitions/deno"
     },

deployment/schema.json

@@ -85,6 +85,12 @@ impl ConfigurationBuilder {
     self.insert("headingKind", value.to_string().into())
   }
 
+  /// The style of list indentation to use.
+  /// Default: `ListIndentKind::CommonMark`
+  pub fn list_indent_kind(&mut self, value: ListIndentKind) -> &mut Self {
+    self.insert("listIndentKind", value.to_string().into())
+  }
+
   /// The directive used to ignore a line.
   /// Default: `dprint-ignore`
   pub fn ignore_directive(&mut self, value: &str) -> &mut Self {
@@ -147,13 +153,14 @@ mod tests {
       .strong_kind(StrongKind::Underscores)
       .unordered_list_kind(UnorderedListKind::Asterisks)
       .heading_kind(HeadingKind::Atx)
+      .list_indent_kind(ListIndentKind::PythonMarkdown)
       .ignore_directive("test")
       .ignore_file_directive("test")
       .ignore_start_directive("test")
       .ignore_end_directive("test");
 
     let inner_config = config.get_inner_config();
-    assert_eq!(inner_config.len(), 11);
+    assert_eq!(inner_config.len(), 12);
     let diagnostics = resolve_config(inner_config, &Default::default()).diagnostics;
     assert_eq!(diagnostics.len(), 0);
   }

src/configuration/builder.rs

@@ -65,6 +65,7 @@ pub fn resolve_config(
       &mut diagnostics,
     ),
     heading_kind: get_value(&mut config, "headingKind", HeadingKind::Atx, &mut diagnostics),
+    list_indent_kind: get_value(&mut config, "listIndentKind", ListIndentKind::CommonMark, &mut diagnostics),
     ignore_directive: get_value(
       &mut config,
       "ignoreDirective",

src/configuration/resolve_config.rs

@@ -16,6 +16,7 @@ pub struct Configuration {
   pub strong_kind: StrongKind,
   pub unordered_list_kind: UnorderedListKind,
   pub heading_kind: HeadingKind,
+  pub list_indent_kind: ListIndentKind,
   pub ignore_directive: String,
   pub ignore_file_directive: String,
   pub ignore_start_directive: String,
@@ -115,3 +116,20 @@ pub enum HeadingKind {
 }
 
 generate_str_to_from![HeadingKind, [Setext, "setext"], [Atx, "atx"]];
+
+/// The style of indentation to use for list items.
+///
+/// CommonMark aligns continuation lines to the content column after the marker
+/// (e.g. 3 spaces for `1. `, 4 spaces for `10. `). PythonMarkdown uses a fixed
+/// 4-space indent regardless of marker width, which is required by tools like
+/// mkdocs-material.
+#[derive(Clone, PartialEq, Copy, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub enum ListIndentKind {
+  /// Indents continuation lines to align with the content after the list marker (default).
+  CommonMark,
+  /// Always indents by 4 spaces, regardless of marker width.
+  PythonMarkdown,
+}
+
+generate_str_to_from![ListIndentKind, [CommonMark, "commonMark"], [PythonMarkdown, "pythonMarkdown"]];

src/configuration/types.rs

@@ -741,7 +741,10 @@ fn gen_list(list: &List, is_alternate: bool, context: &mut Context) -> PrintItem
       } else {
         String::from(context.configuration.unordered_list_kind.list_char(is_alternate))
       };
-      let indent_increment = (prefix_text.chars().count() + 1) as u32;
+      let indent_increment = match context.configuration.list_indent_kind {
+        crate::configuration::ListIndentKind::CommonMark => (prefix_text.chars().count() + 1) as u32,
+        crate::configuration::ListIndentKind::PythonMarkdown => std::cmp::max(prefix_text.chars().count() as u32 + 1, 4),
+      };
       context.indent_level += indent_increment;
       items.push_string(prefix_text);
       let after_child = LineAndColumn::new("afterChild");

src/generation/generate.rs

@@ -0,0 +1,36 @@
+~~ listIndentKind: pythonMarkdown ~~
+!! should indent nested ordered list by 4 spaces !!
+1. first
+   1. nested first
+   2. nested second
+2. second
+
+[expect]
+1. first
+    1. nested first
+    2. nested second
+2. second
+
+!! should indent nested unordered list by 4 spaces !!
+- first
+  - nested first
+  - nested second
+- second
+
+[expect]
+- first
+    - nested first
+    - nested second
+- second
+
+!! should indent double-digit ordered list consistently !!
+9. Testing
+   6. Test
+10. Other
+    7. Testing
+
+[expect]
+9. Testing
+    6. Test
+10. Other
+    7. Testing