[Issue #4108] post_comment_alignment config option

Configurations.md

@@ -1259,6 +1259,40 @@ fn lorem() -> usize {
 
 See also: [`tab_spaces`](#tab_spaces).
 
+## `post_comment_alignment`
+
+Alignment of post comments
+
+- **Default value**: `SingleSpace`
+- **Possible values**: `SingleSpace`, `SameIndent`
+- **Stable**: No
+
+#### `SingleSpace`:
+
+One space between the code and comment.
+
+```rust
+fn foo(
+    a: usize, // Cat
+    b: usize, // Dog
+    c: f32, // Bird
+) {
+}
+```
+
+#### `SameIndent` (default):
+
+Each comment has the same indentation.
+
+```rust
+fn foo(
+    a: usize, // Cat
+    b: usize, // Dog
+    c: f32,   // Bird
+) {
+}
+```
+
 ## `hex_literal_case`
 
 Control the case of the letters in hexadecimal literal values

src/attr.rs

@@ -147,7 +147,7 @@ fn format_derive(
         .tactic(tactic)
         .trailing_separator(trailing_separator)
         .ends_with_newline(false);
-    let item_str = write_list(&all_items, &fmt).ok()?;
+    let item_str = write_list(all_items, &fmt).ok()?;
 
     debug!("item_str: '{}'", item_str);
 

src/closures.rs

@@ -338,7 +338,7 @@ fn rewrite_closure_fn_decl(
     let fmt = ListFormatting::new(param_shape, context.config)
         .tactic(tactic)
         .preserve_newline(true);
-    let list_str = write_list(&item_vec, &fmt)?;
+    let list_str = write_list(item_vec, &fmt)?;
     let mut prefix = format!("{binder}{const_}{immovable}{coro}{capture_str}|{list_str}|");
 
     if !ret_str.is_empty() {

src/config/mod.rs

@@ -81,6 +81,8 @@ create_config! {
         "Format the bodies of declarative macro definitions";
     skip_macro_invocations: SkipMacroInvocations, false,
         "Skip formatting the bodies of macros invoked with the following names.";
+    post_comment_alignment: PostCommentAlignmentConfig, false,
+        "Alignment of post comments";
     hex_literal_case: HexLiteralCaseConfig, true, "Format hexadecimal integer literals";
     float_literal_trailing_zero: FloatLiteralTrailingZeroConfig, false,
         "Add or remove trailing zero in floating-point literals";
@@ -783,6 +785,7 @@ format_strings = false
 format_macro_matchers = false
 format_macro_bodies = true
 skip_macro_invocations = []
+post_comment_alignment = "SingleSpace"
 hex_literal_case = "Preserve"
 float_literal_trailing_zero = "Preserve"
 empty_item_single_line = true
@@ -876,6 +879,7 @@ format_strings = false
 format_macro_matchers = false
 format_macro_bodies = true
 skip_macro_invocations = []
+post_comment_alignment = "SingleSpace"
 hex_literal_case = "Preserve"
 float_literal_trailing_zero = "Preserve"
 empty_item_single_line = true

src/config/options.rs

@@ -160,6 +160,15 @@ pub enum ImportGranularity {
     One,
 }
 
+/// Controls how rustfmt should align post comments.
+#[config_type]
+pub enum PostCommentAlignment {
+    /// Insert one space between the code and comment.
+    SingleSpace,
+    /// List each comment with the same indentation from the previous.
+    SameIndent,
+}
+
 /// Controls how rustfmt should handle case in hexadecimal literals.
 #[config_type]
 pub enum HexLiteralCase {
@@ -653,6 +662,8 @@ config_option_with_style_edition_default!(
     FormatMacroMatchers, bool, _ => false;
     FormatMacroBodies, bool, _ => true;
     SkipMacroInvocations, MacroSelectors, _ => MacroSelectors::default();
+    PostCommentAlignmentConfig, PostCommentAlignment, _ =>
+        PostCommentAlignment::SingleSpace;
     HexLiteralCaseConfig, HexLiteralCase, _ => HexLiteralCase::Preserve;
     FloatLiteralTrailingZeroConfig, FloatLiteralTrailingZero, _ =>
         FloatLiteralTrailingZero::Preserve;

src/expr.rs

@@ -1818,7 +1818,7 @@ fn rewrite_struct_lit<'a>(
             force_no_trailing_comma || has_base_or_rest || !context.use_block_indent(),
         );
 
-        write_list(&item_vec, &fmt)?
+        write_list(item_vec, &fmt)?
     };
 
     let fields_str =
@@ -1965,7 +1965,7 @@ fn rewrite_tuple_in_visual_indent_style<'a, T: 'a + IntoOverflowableItem<'a>>(
     let fmt = ListFormatting::new(nested_shape, context.config)
         .tactic(tactic)
         .ends_with_newline(false);
-    let list_str = write_list(&item_vec, &fmt)?;
+    let list_str = write_list(item_vec, &fmt)?;
 
     Ok(format!("({list_str})"))
 }

src/imports.rs

@@ -1066,7 +1066,7 @@ fn rewrite_nested_use_tree(
         .preserve_newline(true)
         .nested(has_nested_list);
 
-    let list_str = write_list(&list_items, &fmt)?;
+    let list_str = write_list(list_items, &fmt)?;
 
     let result = if (list_str.contains('\n')
         || list_str.len() > remaining_width

src/items.rs

@@ -652,7 +652,7 @@ impl<'a> FmtVisitor<'a> {
             .trailing_separator(self.config.trailing_comma())
             .preserve_newline(true);
 
-        let list = write_list(&items, &fmt).ok()?;
+        let list = write_list(items, &fmt).ok()?;
         result.push_str(&list);
         result.push_str(&original_offset.to_string_with_newline(self.config));
         result.push('}');
@@ -2791,7 +2791,7 @@ struct WhereClauseOption {
     suppress_comma: bool, // Force no trailing comma
     snuggle: WhereClauseSpace,
     allow_single_line: bool, // Try single line where-clause instead of vertical layout
-    veto_single_line: bool,  // Disallow a single-line where-clause.
+    veto_single_line: bool, // Disallow a single-line where-clause.
 }
 
 impl WhereClauseOption {
@@ -2902,7 +2902,7 @@ fn rewrite_params(
         .trailing_separator(trailing_separator)
         .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
         .preserve_newline(true);
-    write_list(&param_items, &fmt)
+    write_list(param_items, &fmt)
 }
 
 fn compute_budgets_for_params(
@@ -2926,7 +2926,7 @@ fn compute_budgets_for_params(
         let overhead = if ret_str_len == 0 { 2 } else { 3 };
         let mut used_space = indent.width() + result.len() + ret_str_len + overhead;
         match fn_brace_style {
-            FnBraceStyle::None => used_space += 1,     // 1 = `;`
+            FnBraceStyle::None => used_space += 1, // 1 = `;`
             FnBraceStyle::SameLine => used_space += 2, // 2 = `{}`
             FnBraceStyle::NextLine => (),
         }
@@ -3164,7 +3164,7 @@ fn rewrite_bounds_on_where_clause(
         .tactic(shape_tactic)
         .trailing_separator(comma_tactic)
         .preserve_newline(preserve_newline);
-    write_list(&items.collect::<Vec<_>>(), &fmt)
+    write_list(items.collect::<Vec<_>>(), &fmt)
 }
 
 fn rewrite_where_clause(
@@ -3245,7 +3245,7 @@ fn rewrite_where_clause(
         .trailing_separator(comma_tactic)
         .ends_with_newline(tactic.ends_with_newline(context.config.indent_style()))
         .preserve_newline(true);
-    let preds_str = write_list(&item_vec, &fmt)?;
+    let preds_str = write_list(item_vec, &fmt)?;
 
     let end_length = if terminator == "{" {
         // If the brace is on the next line we don't need to count it otherwise it needs two