feat!: preserve line breaks between consecutive comments in pretty mode

sqlglot/generator.py

@@ -1007,23 +1007,24 @@ def maybe_comment(
         if not comments or isinstance(expression, self.EXCLUDE_COMMENTS):
             return sql
 
-        comments_sql = " ".join(
-            f"/*{self.sanitize_comment(comment)}*/" for comment in comments if comment
-        )
+        comments_list = [
+            f"/*{self._replace_line_breaks(self.sanitize_comment(comment))}*/"
+            for comment in comments
+            if comment
+        ]
 
-        if not comments_sql:
+        if not comments_list:
             return sql
 
-        comments_sql = self._replace_line_breaks(comments_sql)
-
         if separated or isinstance(expression, self.WITH_SEPARATED_COMMENTS):
+            comments_sql = self.sep().join(comments_list)
             return (
                 f"{self.sep()}{comments_sql}{sql}"
                 if not sql or sql[0].isspace()
                 else f"{comments_sql}{self.sep()}{sql}"
             )
 
-        return f"{sql} {comments_sql}"
+        return f"{sql} {' '.join(comments_list)}"
 
     def wrap(self, expression: exp.Expr | str) -> str:
         this_sql = (

tests/test_transpile.py

@@ -216,7 +216,9 @@ def test_comments(self):
 -- comment 2
 -- comment 3
 SELECT * FROM foo""",
-            """/* comment 1 */ /* comment 2 */ /* comment 3 */
+            """/* comment 1 */
+/* comment 2 */
+/* comment 3 */
 SELECT
   *
 FROM foo""",
@@ -367,7 +369,9 @@ def test_comments(self):
             -- comment3
             DROP TABLE IF EXISTS db.tba
             """,
-            """/* comment1 */ /* comment2 */ /* comment3 */
+            """/* comment1 */
+/* comment2 */
+/* comment3 */
 DROP TABLE IF EXISTS db.tba""",
             pretty=True,
         )
@@ -428,7 +432,8 @@ def test_comments(self):
             """SELECT
   *
 FROM a
-/* comment 1 */ /* comment 2 */
+/* comment 1 */
+/* comment 2 */
 LEFT OUTER JOIN b""",
             pretty=True,
         )
@@ -619,7 +624,8 @@ def test_comments(self):
   SELECT
     2 AS n /* b */
   FROM (
-    /* c */ /* c2 */
+    /* c */
+    /* c2 */
     SELECT
       a /* d */
     FROM t
@@ -639,6 +645,26 @@ def test_comments(self):
             pretty=True,
         )
 
+        # Round-trip stress: multiple trailing comments on the same expression must
+        # stay space-separated (same line) in pretty mode. Re-parsing would otherwise
+        # detach the later ones onto the next token.
+        self.validate(
+            "SELECT a /* foo */ /* bar */ FROM tbl",
+            """SELECT
+  a /* foo */ /* bar */
+FROM tbl""",
+            pretty=True,
+        )
+        self.validate(
+            "SELECT x FROM t WHERE x = 1 /* a */ /* b */ /* c */",
+            """SELECT
+  x
+FROM t
+WHERE
+  x = 1 /* a */ /* b */ /* c */""",
+            pretty=True,
+        )
+
         self.validate(
             """SELECT
   *