fix: tweak solution, add more tests, update changelog

Author: tconbeer

CHANGELOG.md

@@ -7,6 +7,7 @@ All notable changes to this project will be documented in this file.
 ### Formatting Changes and Bug Fixes
 
 - sqlfmt now lexes and formats BigQuery hexadecimal literals as numbers, and no longer adds a space between `0` and `x` ([#696](https://github.com/tconbeer/sqlfmt/issues/696) - thank you [@KMontag42](https://github.com/KMontag42) and [@snrsw](https://github.com/snrsw)!).
+- sqlfmt no longer adds a second blank newline to the end of a query that only contains a comment (with no sql code) ([#686](https://github.com/tconbeer/sqlfmt/issues/686) - thank you [@nevdelap](https://github.com/nevdelap) and [@snrsw](https://github.com/snrsw)!).
 
 ## [0.27.0] - 2025-07-28
 

src/sqlfmt/line.py

@@ -105,7 +105,10 @@ def render_with_comments(self, max_length: int) -> str:
 
         if inline_comments:
             rendered_lines.append(f"{content}{''.join(inline_comments)}\n")
-        else:
+        # if content is empty AND we've already rendered a standalone or multiline
+        # comment, skip rendering the line itself, since that just adds a duplicate
+        # newline.
+        elif content or not self.comments:
             rendered_lines.append(f"{self}")
 
         return "".join(rendered_lines)

src/sqlfmt/query.py

@@ -32,8 +32,5 @@ def nodes(self) -> List[Node]:
         return nodes
 
     def __str__(self) -> str:
-        if not self.lines:
-            return ""
-
         draft = [line.render_with_comments(self.line_length) for line in self.lines]
-        return "".join(draft).rstrip("\n") + "\n"
+        return "".join(draft)

tests/data/preformatted/009_empty.sql

@@ -0,0 +1 @@
+-- a comment

tests/data/preformatted/010_comment_only.sql

@@ -16,6 +16,8 @@
         "preformatted/006_fmt_off_447.sql",
         "preformatted/007_fmt_off_comments.sql",
         "preformatted/008_reserved_names.sql",
+        "preformatted/009_empty.sql",
+        "preformatted/010_comment_only.sql",
         "preformatted/301_multiline_jinjafmt.sql",
         "preformatted/302_jinjafmt_multiline_str.sql",
         "preformatted/303_jinjafmt_more_mutliline_str.sql",

tests/functional_tests/test_general_formatting.py

@@ -1,3 +1,5 @@
+import pytest
+
 from sqlfmt.analyzer import Analyzer
 
 
@@ -13,3 +15,10 @@ def test_only_comment_formatting(default_analyzer: Analyzer) -> None:
     expected_string = "-- a comment\n"
     q = default_analyzer.parse_query(source_string=source_string)
     assert str(q) == expected_string
+
+
+@pytest.mark.parametrize("source_string", ["", "\n"])
+def test_empty_formatting(default_analyzer: Analyzer, source_string: str) -> None:
+    expected_string = ""
+    q = default_analyzer.parse_query(source_string=source_string)
+    assert str(q) == expected_string