Use blank_lines_* to control newlines between module level attrs

src/attr.rs

@@ -8,8 +8,10 @@ use self::doc_comment::DocCommentFormatter;
 use crate::comment::{contains_comment, rewrite_doc_comment, CommentStyle};
 use crate::config::lists::*;
 use crate::config::IndentStyle;
+use crate::config::Version;
 use crate::expr::rewrite_literal;
 use crate::lists::{definitive_tactic, itemize_list, write_list, ListFormatting, Separator};
+use crate::missed_spans::push_vertical_spaces;
 use crate::overflow;
 use crate::rewrite::{Rewrite, RewriteContext};
 use crate::shape::Shape;
@@ -419,6 +421,7 @@ impl Rewrite for [ast::Attribute] {
                         shape.with_max_width(context.config),
                         context,
                         0,
+                        false,
                     )?;
                     let comment = if comment.is_empty() {
                         format!("\n{}", mlb)
@@ -449,6 +452,7 @@ impl Rewrite for [ast::Attribute] {
                         shape.with_max_width(context.config),
                         context,
                         0,
+                        false,
                     )?;
                     result.push_str(&comment);
                     if let Some(next) = attrs.get(derives.len()) {
@@ -476,12 +480,25 @@ impl Rewrite for [ast::Attribute] {
             let missing_span = attrs
                 .get(1)
                 .map(|next| mk_sp(attrs[0].span.hi(), next.span.lo()));
+
+            let mut vertical_lines_pushed = 0;
             if let Some(missing_span) = missing_span {
+                let snippet = context.snippet(missing_span);
+                if let Some((whitespace, _)) = snippet.split_once(|c: char| !c.is_whitespace()) {
+                    let newlines = count_newlines(whitespace);
+                    // Version gate this change as it leads to breaking changes with Version::One
+                    if newlines > 0 && context.config.version() == Version::Two {
+                        vertical_lines_pushed =
+                            push_vertical_spaces(&mut result, context.config, newlines);
+                    }
+                }
+                // remove leading newlines if we already pushed vertical space into the result
                 let comment = crate::comment::recover_missing_comment_in_span(
                     missing_span,
                     shape.with_max_width(context.config),
                     context,
                     0,
+                    vertical_lines_pushed > 0,
                 )?;
                 result.push_str(&comment);
                 if let Some(next) = attrs.get(1) {

src/comment.rs

@@ -965,6 +965,7 @@ pub(crate) fn recover_missing_comment_in_span(
     shape: Shape,
     context: &RewriteContext<'_>,
     used_width: usize,
+    remove_leading_newlines: bool,
 ) -> Option<String> {
     let missing_comment = rewrite_missing_comment(span, shape, context)?;
     if missing_comment.is_empty() {
@@ -976,7 +977,9 @@ pub(crate) fn recover_missing_comment_in_span(
         let total_width = missing_comment.len() + used_width + 1;
         let force_new_line_before_comment =
             missing_snippet[..pos].contains('\n') || total_width > context.config.max_width();
-        let sep = if force_new_line_before_comment {
+        let sep = if remove_leading_newlines && force_new_line_before_comment {
+            shape.indent.to_string(context.config)
+        } else if force_new_line_before_comment {
             shape.indent.to_string_with_newline(context.config)
         } else {
             Cow::from(" ")

src/items.rs

@@ -713,6 +713,7 @@ pub(crate) fn format_impl(
                 Shape::indented(offset, context.config),
                 context,
                 last_line_width(&result),
+                false,
             ) {
                 Some(ref missing_comment) if !missing_comment.is_empty() => {
                     result.push_str(missing_comment);
@@ -1092,6 +1093,7 @@ pub(crate) fn format_trait(
                         Shape::indented(offset, context.config),
                         context,
                         last_line_width(&result),
+                        false,
                     ) {
                         Some(ref missing_comment) if !missing_comment.is_empty() => {
                             result.push_str(missing_comment);
@@ -2482,6 +2484,7 @@ fn rewrite_fn_base(
                 shape,
                 context,
                 last_line_width(&result),
+                false,
             ) {
                 Some(ref missing_comment) if !missing_comment.is_empty() => {
                     result.push_str(missing_comment);

src/missed_spans.rs

@@ -9,6 +9,7 @@ use crate::shape::{Indent, Shape};
 use crate::source_map::LineRangeUtils;
 use crate::utils::{count_lf_crlf, count_newlines, last_line_width, mk_sp};
 use crate::visitor::FmtVisitor;
+use crate::Config;
 
 struct SnippetStatus {
     /// An offset to the current line from the beginning of the original snippet.
@@ -112,27 +113,9 @@ impl<'a> FmtVisitor<'a> {
         }
     }
 
-    fn push_vertical_spaces(&mut self, mut newline_count: usize) {
-        let offset = self.buffer.chars().rev().take_while(|c| *c == '\n').count();
-        let newline_upper_bound = self.config.blank_lines_upper_bound() + 1;
-        let newline_lower_bound = self.config.blank_lines_lower_bound() + 1;
-
-        if newline_count + offset > newline_upper_bound {
-            if offset >= newline_upper_bound {
-                newline_count = 0;
-            } else {
-                newline_count = newline_upper_bound - offset;
-            }
-        } else if newline_count + offset < newline_lower_bound {
-            if offset >= newline_lower_bound {
-                newline_count = 0;
-            } else {
-                newline_count = newline_lower_bound - offset;
-            }
-        }
-
-        let blank_lines = "\n".repeat(newline_count);
-        self.push_str(&blank_lines);
+    fn push_vertical_spaces(&mut self, newline_count: usize) {
+        let newlines_pushed = push_vertical_spaces(&mut self.buffer, self.config, newline_count);
+        self.line_number += newlines_pushed;
     }
 
     fn write_snippet<F>(&mut self, span: Span, process_last_snippet: F)
@@ -361,3 +344,31 @@ impl<'a> FmtVisitor<'a> {
         }
     }
 }
+
+pub(crate) fn push_vertical_spaces(
+    buffer: &mut String,
+    config: &Config,
+    mut newline_count: usize,
+) -> usize {
+    let offset = buffer.chars().rev().take_while(|c| *c == '\n').count();
+    let newline_upper_bound = config.blank_lines_upper_bound() + 1;
+    let newline_lower_bound = config.blank_lines_lower_bound() + 1;
+
+    if newline_count + offset > newline_upper_bound {
+        if offset >= newline_upper_bound {
+            newline_count = 0;
+        } else {
+            newline_count = newline_upper_bound - offset;
+        }
+    } else if newline_count + offset < newline_lower_bound {
+        if offset >= newline_lower_bound {
+            newline_count = 0;
+        } else {
+            newline_count = newline_lower_bound - offset;
+        }
+    }
+
+    let blank_lines = "\n".repeat(newline_count);
+    buffer.push_str(&blank_lines);
+    newline_count
+}

tests/source/issue-4082/version_one/original_example.rs

@@ -0,0 +1,18 @@
+// rustfmt-version: One
+
+#![feature(core_intrinsics)]
+#![feature(lang_items)]
+#![feature(libc)]
+#![feature(nll)]
+#![feature(panic_unwind)]
+#![feature(staged_api)]
+#![feature(std_internals)]
+#![feature(unwind_attributes)]
+#![feature(abi_thiscall)]
+#![feature(rustc_attrs)]
+#![feature(raw)]
+#![panic_runtime]
+#![feature(panic_runtime)]
+
+// `real_imp` is unused with Miri, so silence warnings.
+#![cfg_attr(miri, allow(dead_code))]

tests/source/issue-4082/version_two/add_newlines.rs

@@ -0,0 +1,19 @@
+// rustfmt-version: Two
+// rustfmt-blank_lines_upper_bound: 2
+// rustfmt-blank_lines_lower_bound: 2
+#![feature(core_intrinsics)]
+#![feature(lang_items)]
+#![feature(libc)]
+#![feature(nll)]
+#![feature(panic_unwind)]
+#![feature(staged_api)]
+#![feature(std_internals)]
+#![feature(unwind_attributes)]
+#![feature(abi_thiscall)]
+#![feature(rustc_attrs)]
+#![feature(raw)]
+#![panic_runtime]
+#![feature(panic_runtime)]
+
+// `real_imp` is unused with Miri, so silence warnings.
+#![cfg_attr(miri, allow(dead_code))]

tests/source/issue-4082/version_two/remove_newlines.rs

@@ -0,0 +1,23 @@
+// rustfmt-version: Two
+// rustfmt-blank_lines_upper_bound: 2
+// rustfmt-blank_lines_lower_bound: 2
+#![feature(core_intrinsics)]
+#![feature(lang_items)]
+#![feature(libc)]
+#![feature(nll)]
+#![feature(panic_unwind)]
+#![feature(staged_api)]
+#![feature(std_internals)]
+#![feature(unwind_attributes)]
+#![feature(abi_thiscall)]
+#![feature(rustc_attrs)]
+#![feature(raw)]
+#![panic_runtime]
+#![feature(panic_runtime)]
+
+
+
+
+
+// `real_imp` is unused with Miri, so silence warnings.
+#![cfg_attr(miri, allow(dead_code))]

tests/target/issue-4082/version_one/original_example.rs

@@ -0,0 +1,17 @@
+// rustfmt-version: One
+
+#![feature(core_intrinsics)]
+#![feature(lang_items)]
+#![feature(libc)]
+#![feature(nll)]
+#![feature(panic_unwind)]
+#![feature(staged_api)]
+#![feature(std_internals)]
+#![feature(unwind_attributes)]
+#![feature(abi_thiscall)]
+#![feature(rustc_attrs)]
+#![feature(raw)]
+#![panic_runtime]
+#![feature(panic_runtime)]
+// `real_imp` is unused with Miri, so silence warnings.
+#![cfg_attr(miri, allow(dead_code))]

tests/target/issue-4082/version_two/add_newlines.rs

@@ -0,0 +1,20 @@
+// rustfmt-version: Two
+// rustfmt-blank_lines_upper_bound: 2
+// rustfmt-blank_lines_lower_bound: 2
+#![feature(core_intrinsics)]
+#![feature(lang_items)]
+#![feature(libc)]
+#![feature(nll)]
+#![feature(panic_unwind)]
+#![feature(staged_api)]
+#![feature(std_internals)]
+#![feature(unwind_attributes)]
+#![feature(abi_thiscall)]
+#![feature(rustc_attrs)]
+#![feature(raw)]
+#![panic_runtime]
+#![feature(panic_runtime)]
+
+
+// `real_imp` is unused with Miri, so silence warnings.
+#![cfg_attr(miri, allow(dead_code))]

tests/target/issue-4082/version_two/original_example.rs

@@ -0,0 +1,18 @@
+// rustfmt-version: Two
+
+#![feature(core_intrinsics)]
+#![feature(lang_items)]
+#![feature(libc)]
+#![feature(nll)]
+#![feature(panic_unwind)]
+#![feature(staged_api)]
+#![feature(std_internals)]
+#![feature(unwind_attributes)]
+#![feature(abi_thiscall)]
+#![feature(rustc_attrs)]
+#![feature(raw)]
+#![panic_runtime]
+#![feature(panic_runtime)]
+
+// `real_imp` is unused with Miri, so silence warnings.
+#![cfg_attr(miri, allow(dead_code))]

tests/target/issue-4082/version_two/remove_newlines.rs

@@ -0,0 +1,20 @@
+// rustfmt-version: Two
+// rustfmt-blank_lines_upper_bound: 2
+// rustfmt-blank_lines_lower_bound: 2
+#![feature(core_intrinsics)]
+#![feature(lang_items)]
+#![feature(libc)]
+#![feature(nll)]
+#![feature(panic_unwind)]
+#![feature(staged_api)]
+#![feature(std_internals)]
+#![feature(unwind_attributes)]
+#![feature(abi_thiscall)]
+#![feature(rustc_attrs)]
+#![feature(raw)]
+#![panic_runtime]
+#![feature(panic_runtime)]
+
+
+// `real_imp` is unused with Miri, so silence warnings.
+#![cfg_attr(miri, allow(dead_code))]