[Analyzer] Keep comments when organizing imports

This change adjusts the organize imports logic, to keep any comments
written in the line above an import statement attached when
organizing the imports, while being smart about what comments to keep.

Closes https://github.com/dart-lang/sdk/issues/42515
Change-Id: Ibcca4f24411ac16bcdb17f66fb6d2b9c45f7d367
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/157743
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/src/services/correction/organize_imports.dart

@@ -64,6 +64,34 @@ class ImportOrganizer {
         var priority = getDirectivePriority(directive);
         if (priority != null) {
           var offset = directive.offset;
+          if (directive.beginToken.precedingComments != null) {
+            var firstComment = directive.beginToken.precedingComments;
+            var comment = firstComment;
+            // Don't connect comments that have a blank line between them
+            while (comment.next != null) {
+              var currentLine = lineInfo.getLocation(comment.offset).lineNumber;
+              var nextLine =
+                  lineInfo.getLocation(comment.next.offset).lineNumber;
+              if (nextLine - currentLine > 1) {
+                firstComment = comment.next;
+              }
+
+              comment = comment.next;
+            }
+            // Check if the comment is the first comment in the document
+            if (firstComment != unit.beginToken.precedingComments) {
+              var previousLine = lineInfo
+                  .getLocation(directive.beginToken.previous.end)
+                  .lineNumber;
+
+              // Check if the comment is after the last token of the previous line
+              // Only connect, if it's not on the same line as the last token of the previous line
+              if (lineInfo.getLocation(firstComment.offset).lineNumber !=
+                  previousLine) {
+                offset = firstComment.offset;
+              }
+            }
+          }
 
           var end = directive.end;
           var line = lineInfo.getLocation(end).lineNumber;

pkg/analysis_server/test/services/correction/organize_directives_test.dart

@@ -290,6 +290,53 @@ main() {
 ''');
   }
 
+  Future<void>
+      test_sort_imports_dontConnectFirstCommentsWithBlankLinesBetween() async {
+    await _computeUnitAndErrors(r'''
+// Copyright...
+
+// Some comment related to the line below
+import 'package:b/a.dart';
+import 'package:a/b.dart';''');
+    _assertOrganize(r'''
+// Copyright...
+
+import 'package:a/b.dart';
+// Some comment related to the line below
+import 'package:b/a.dart';''');
+  }
+
+  Future<void> test_sort_imports_keepFirstCommentUntouched() async {
+    await _computeUnitAndErrors(r'''
+// Copyright
+// Copyright2
+// Copyright3
+import 'package:b/a.dart';
+import 'package:a/b.dart';''');
+
+    _assertOrganize(r'''
+// Copyright
+// Copyright2
+// Copyright3
+import 'package:a/b.dart';
+import 'package:b/a.dart';''');
+  }
+
+  Future<void> test_sort_imports_keepSubsequentComments() async {
+    await _computeUnitAndErrors(r'''
+/// Copyright...
+library lib;
+
+import 'package:b/a.dart'; // We are keeping this because ...
+import 'package:a/b.dart';''');
+    _assertOrganize(r'''
+/// Copyright...
+library lib;
+
+import 'package:a/b.dart';
+import 'package:b/a.dart'; // We are keeping this because ...''');
+  }
+
   Future<void> test_sort_imports_packageAndPath() async {
     await _computeUnitAndErrors(r'''
 library lib;
@@ -314,6 +361,36 @@ import 'package:product2.client/entity.dart';
 ''');
   }
 
+  Future<void> test_sort_imports_with_library_keepPrecedingComments() async {
+    await _computeUnitAndErrors(r'''
+/// Copyright...
+library lib;
+
+// Test comment
+
+// We are keeping this because ... l1
+// We are keeping this because ... l2
+// We are keeping this because ... l3
+import 'package:b/a.dart';
+// Comment for a
+
+import 'package:a/b.dart';''');
+
+    _assertOrganize(r'''
+/// Copyright...
+library lib;
+
+// Test comment
+
+// Comment for a
+
+import 'package:a/b.dart';
+// We are keeping this because ... l1
+// We are keeping this because ... l2
+// We are keeping this because ... l3
+import 'package:b/a.dart';''');
+  }
+
   void _assertOrganize(String expectedCode, {bool removeUnused = false}) {
     var organizer = ImportOrganizer(testCode, testUnit, testErrors,
         removeUnused: removeUnused);