Fixed first comment and last comment not reordering issue

src/formatting/comment.rs

@@ -156,6 +156,11 @@ pub(crate) fn is_last_comment_block(s: &str) -> bool {
     s.trim_end().ends_with("*/")
 }
 
+/// Returns true if the first line of the passed string started with a block-comment.
+pub(crate) fn is_first_comment_block(s: &str) -> bool {
+    s.trim_start().starts_with("/*")
+}
+
 /// Combine `prev_str` and `next_str` into a single `String`. `span` may contain
 /// comments between two strings. If there are such comments, then that will be
 /// recovered. If `allow_extend` is true and there is no comment between the two

src/formatting/lists.rs

@@ -8,12 +8,14 @@ use unicode_segmentation::UnicodeSegmentation;
 
 use crate::config::{lists::*, Config, IndentStyle};
 use crate::formatting::{
-    comment::{comment_style, find_comment_end, rewrite_comment, FindUncommented},
+    comment::{
+        comment_style, find_comment_end, is_last_comment_block, rewrite_comment, FindUncommented,
+    },
     rewrite::RewriteContext,
     shape::{Indent, Shape},
     utils::{
-        count_newlines, first_line_width, last_line_width, mk_sp, starts_with_newline,
-        unicode_str_width,
+        count_newlines, first_line_width, last_line_contains_single_line_comment, last_line_width,
+        mk_sp, starts_with_newline, unicode_str_width,
     },
     visitor::SnippetProvider,
 };
@@ -281,6 +283,10 @@ where
 
     let mut line_len = 0;
     let indent_str = &formatting.shape.indent.to_string(formatting.config);
+    let newline_str = &formatting
+        .shape
+        .indent
+        .to_string_with_newline(formatting.config);
     while let Some((i, item)) = iter.next() {
         let item = item.as_ref();
         let inner_item = item.item.as_ref()?;
@@ -291,6 +297,8 @@ where
             SeparatorPlace::Back => !last || trailing_separator,
         };
         let item_sep_len = if separate { sep_len } else { 0 };
+        let item_has_comments = item.post_comment.is_some() || item.pre_comment.is_some();
+        let item_has_both_comments = item.post_comment.is_some() && item.pre_comment.is_some();
 
         // Item string may be multi-line. Its length (used for block comment alignment)
         // should be only the length of the last line.
@@ -318,17 +326,17 @@ where
                 } else if i < num_args_before {
                     result.push(' ');
                 } else if i <= num_args_before + 1 {
-                    result.push('\n');
-                    result.push_str(indent_str);
+                    result.push_str(newline_str);
                 } else {
                     result.push(' ');
                 }
             }
             DefinitiveListTactic::Vertical
-                if !first && !inner_item.is_empty() && !result.is_empty() =>
+                if !first
+                    && (!inner_item.is_empty() || item_has_comments)
+                    && !result.is_empty() =>
             {
-                result.push('\n');
-                result.push_str(indent_str);
+                result.push_str(newline_str);
             }
             DefinitiveListTactic::Mixed => {
                 let total_width = total_item_width(item) + item_sep_len;
@@ -385,8 +393,7 @@ where
                     if keep_comment {
                         result.push(' ');
                     } else {
-                        result.push('\n');
-                        result.push_str(indent_str);
+                        result.push_str(newline_str);
                         // This is the width of the item (without comments).
                         line_len = item.item.as_ref().map_or(0, |s| unicode_str_width(&s));
                     }
@@ -397,7 +404,9 @@ where
             item_max_width = None;
         }
 
-        if separate && sep_place.is_front() && !first {
+        if inner_item.is_empty() && item_has_both_comments {
+            result.push_str(newline_str);
+        } else if separate && sep_place.is_front() && !first {
             result.push_str(formatting.separator.trim());
             result.push(' ');
         }
@@ -461,7 +470,7 @@ where
                         formatting.config.max_width(),
                     ));
                 }
-                let overhead = if starts_with_newline(comment) {
+                let overhead = if starts_with_newline(comment) || inner_item.is_empty() {
                     0
                 } else if let Some(max_width) = *item_max_width {
                     max_width + 2
@@ -471,6 +480,7 @@ where
                 };
                 let width = formatting.shape.width.checked_sub(overhead).unwrap_or(1);
                 let offset = formatting.shape.indent + overhead;
+
                 let comment_start_trimmed = comment.trim_start();
 
                 // Find if first comment is single line and the end of the first comment
@@ -589,11 +599,12 @@ where
                 }
                 // An additional space for the missing trailing separator (or
                 // if we skipped alignment above).
-                if !formatting.align_comments
-                    || (last
-                        && item_max_width.is_some()
-                        && !separate
-                        && !formatting.separator.is_empty())
+                if !inner_item.is_empty()
+                    && (!formatting.align_comments
+                        || (last
+                            && item_max_width.is_some()
+                            && !separate
+                            && !formatting.separator.is_empty()))
                 {
                     result.push(' ');
                 }
@@ -860,22 +871,31 @@ where
                 .span_to_snippet(mk_sp(self.prev_span_end, (self.get_lo)(&item)))
                 .unwrap_or("");
             let (pre_comment, pre_comment_style) = extract_pre_comment(pre_snippet);
+            let next_item = self.inner.peek();
 
             // Post-comment
-            let next_start = match self.inner.peek() {
+            let next_start = match next_item {
                 Some(next_item) => (self.get_lo)(next_item),
                 None => self.next_span_start,
             };
             let post_snippet = self
                 .snippet_provider
                 .span_to_snippet(mk_sp((self.get_hi)(&item), next_start))
                 .unwrap_or("");
-            let comment_end = get_comment_end(
-                post_snippet,
-                self.separator,
-                self.terminator,
-                self.inner.peek().is_none(),
-            );
+            let comment_end = if next_item.is_none()
+                && (last_line_contains_single_line_comment(post_snippet)
+                    || is_last_comment_block(post_snippet))
+            {
+                // To get the trailing single line comment of the last item
+                post_snippet.len()
+            } else {
+                get_comment_end(
+                    post_snippet,
+                    self.separator,
+                    self.terminator,
+                    self.inner.peek().is_none(),
+                )
+            };
             let new_lines = has_extra_newline(post_snippet, comment_end);
             let post_comment = extract_post_comment(post_snippet, comment_end, self.separator);
 

src/formatting/reorder.rs

@@ -9,12 +9,13 @@
 use std::cmp::{Ord, Ordering};
 
 use rustc_ast::ast;
-use rustc_span::{symbol::sym, Span};
+use rustc_span::{symbol::sym, BytePos, Pos, Span};
 
 use crate::config::{Config, GroupImportsTactic, ImportGranularity};
 use crate::formatting::imports::{flatten_use_trees, UseSegment};
 use crate::formatting::modules::{get_mod_inner_attrs, FileModMap};
 use crate::formatting::{
+    comment::{comment_style, contains_comment, is_first_comment_block, is_last_comment_block},
     imports::{merge_use_trees, UseTree},
     items::{is_mod_decl, rewrite_extern_crate, rewrite_mod},
     lists::{itemize_list, write_list, ListFormatting, ListItem},
@@ -413,8 +414,41 @@ impl<'b, 'a: 'b> FmtVisitor<'a> {
 
         if at_least_one_in_file_lines && !items.is_empty() {
             self.normalize_vertical_spaces = true;
-            let lo = items.first().unwrap().span().lo();
-            let hi = items.last().unwrap().span().hi();
+            let context = self.get_context();
+
+            let first_lo = items.first().unwrap().span().lo();
+            let line_lo = self.parse_sess.line_bounds(first_lo).unwrap().start;
+            let leading_snip = context.snippet(mk_sp(line_lo, first_lo));
+            let lo = if contains_comment(leading_snip) {
+                let comment_started = if is_last_comment_block(leading_snip) {
+                    is_first_comment_block(leading_snip)
+                } else {
+                    true
+                };
+                if comment_started { line_lo } else { first_lo }
+            } else {
+                first_lo
+            };
+
+            let last_hi = items.last().unwrap().span().hi();
+            let line_hi = self.parse_sess.line_bounds(last_hi).unwrap().end;
+            let trailing_snip = context.snippet(mk_sp(last_hi, line_hi));
+            let hi = if contains_comment(trailing_snip) {
+                let comment_ended = if is_first_comment_block(trailing_snip) {
+                    is_last_comment_block(trailing_snip.trim())
+                } else {
+                    true
+                };
+                if comment_ended {
+                    // 1 = '\n'
+                    line_hi - BytePos::from_usize(1)
+                } else {
+                    last_hi
+                }
+            } else {
+                last_hi
+            };
+
             let span = mk_sp(lo, hi);
             let rw = rewrite_reorderable_or_regroupable_items(
                 &self.get_context(),

src/formatting/syntux/session.rs

@@ -1,4 +1,5 @@
 use std::cell::RefCell;
+use std::ops::Range;
 use std::path::Path;
 use std::rc::Rc;
 
@@ -189,6 +190,15 @@ impl ParseSess {
         }
     }
 
+    pub(crate) fn line_bounds(&self, pos: BytePos) -> Option<Range<BytePos>> {
+        let line = self.parse_sess.source_map().lookup_line(pos).ok();
+
+        match line {
+            Some(line_info) => Some(line_info.sf.line_bounds(line_info.line)),
+            None => None,
+        }
+    }
+
     pub(crate) fn line_of_byte_pos(&self, pos: BytePos) -> usize {
         self.parse_sess.source_map().lookup_char_pos(pos).line
     }

tests/source/issue-3127.rs

@@ -0,0 +1,3 @@
+extern crate serde; // 1.0.78
+extern crate serde_json; // 1.0.27
+extern crate serde_derive; // 1.0.78

tests/source/issue-3720.rs

@@ -0,0 +1,3 @@
+use c; // use c;
+use b; // use b;
+use a; // use a;

tests/source/issue-4027.rs

@@ -0,0 +1,2 @@
+pub use views::*;
+pub use foo::bar; // re-export for frontend

tests/source/reorder_imports_comments.rs

@@ -0,0 +1,62 @@
+// #4027
+pub use views::*;
+pub use foo::bar; // re-export for frontend
+
+// #3720
+use c; // use c;
+use b; // use b;
+use a; // use a;
+
+// #3127
+extern crate serde; // 1.0.78
+extern crate serde_json; // 1.0.27
+extern crate serde_derive; // 1.0.78
+
+mod c;
+mod b;
+mod a;
+
+/*dpre*/ use d; // dpost
+/*cpre*/ use c; // cpost
+/*bpre*/ use b; // bpost
+/*apre*/ use a; // apost
+
+use std::{};
+use std::borrow::Cow;
+
+/* comment 1 */ use std::{};
+/* comment 2 */ use std::{};
+/* comment 3 */ use std::{};
+
+use std::{}; /* comment 1 */
+use std::{}; /* comment 2 */
+use std::{}; /* comment 3 */
+
+/* comment cpre */ use std::{}; /* comment cpost */
+/* comment bpre */ use std::{}; /* comment bpost */
+/* comment dpre */ use std::{}; /* comment dpost */
+
+/* comment 1 */ use a;
+/* comment 2 */ use b;
+/* comment 3 */ use c;
+
+use std::a; /* comment 1 */
+use std::b; /* comment 2 */
+use std::c; /* comment 3 */
+
+/* comment cpre */ use std::c; /* comment cpost */
+/* comment bpre */ use std::b; /* comment bpost */
+/* comment dpre */ use std::a; /* comment dpost */
+
+
+/* comment 1 */ use std::{}; // Comment 1
+/* comment 2 */ use std::{}; // Comment 2
+/* comment 3 */ use std::{}; // Comment 3
+
+
+/* Comment
+A */ use a; // Comment A
+/* Comment B */ use b; // Comment B
+/* Comment C */ use c; // Comment C
+/* Comment D */ use d; /* Comment
+D */

tests/target/issue-3127.rs

@@ -0,0 +1,3 @@
+extern crate serde; // 1.0.78
+extern crate serde_derive; // 1.0.78
+extern crate serde_json; // 1.0.27

tests/target/issue-3720.rs

@@ -0,0 +1,3 @@
+use a; // use a;
+use b; // use b;
+use c; // use c;

tests/target/issue-4027.rs

@@ -0,0 +1,2 @@
+pub use foo::bar; // re-export for frontend
+pub use views::*;