fix: resolve several empty line regressions (#330)

* fix: add function to check if docstring is at end of file

* fix: handle case where class contains only docstring

* chore: fix mypy error

* fix: treat ellipses as code line

* fix: include workaround to detect f-string in Python < 3.12

* fix: refine newline detection to exclude empty lines

Author: finswimmer

src/docformatter/classify.py

@@ -266,7 +266,7 @@ def is_code_line(token: tokenize.TokenInfo) -> bool:
     bool
         True if the token is a code line, False otherwise.
     """
-    if token.type == tokenize.NAME and not (
+    if (token.type == tokenize.NAME or token.string == "...") and not (
         token.line.strip().startswith("def ")
         or token.line.strip().startswith("async ")
         or token.line.strip().startswith("class ")
@@ -317,6 +317,15 @@ def is_f_string(token: tokenize.TokenInfo, prev_token: tokenize.TokenInfo) -> bo
     if PY312:
         if tokenize.FSTRING_MIDDLE in [token.type, prev_token.type]:
             return True
+    elif any(
+        [
+            token.string.startswith('f"""'),
+            prev_token.string.startswith('f"""'),
+            token.string.startswith("f'''"),
+            prev_token.string.startswith("f'''"),
+        ]
+    ):
+        return True
 
     return False
 
@@ -432,7 +441,7 @@ def is_newline_continuation(
     if (
         token.type in (tokenize.NEWLINE, tokenize.NL)
         and token.line.strip() in prev_token.line.strip()
-        and token.line != "\n"
+        and token.line not in {"\n", "\r\n"}
     ):
         return True
 
@@ -460,14 +469,29 @@ def is_string_variable(
     # TODO: The AWAIT token is removed in Python 3.13 and later.  Only Python 3.9
     # seems to generate the AWAIT token, so we can safely remove the check for it when
     # support for Python 3.9 is dropped in April 2026.
-    try:
+    if sys.version_info <= (3, 12):
         _token_types = (tokenize.AWAIT, tokenize.OP)
-    except AttributeError:
-        _token_types = (tokenize.OP,)  # type: ignore
+    else:
+        _token_types = (tokenize.OP,)
 
     if prev_token.type in _token_types and (
         '= """' in token.line or token.line in prev_token.line
     ):
         return True
 
     return False
+
+
+def is_docstring_at_end_of_file(tokens: list[tokenize.TokenInfo], index: int) -> bool:
+    """Determine if the docstring is at the end of the file."""
+    for i in range(index + 1, len(tokens)):
+        tok = tokens[i]
+        if tok.type not in (
+            tokenize.NL,
+            tokenize.NEWLINE,
+            tokenize.DEDENT,
+            tokenize.ENDMARKER,
+        ):
+            return False
+
+    return True

src/docformatter/format.py

@@ -260,11 +260,22 @@ def _get_class_docstring_newlines(
         The number of newlines to insert after the docstring.
     """
     j = index + 1
+    indention_level = tokens[index].start[1]
 
     # The docstring is followed by a comment.
     if tokens[j].string.startswith("#"):
         return 0
 
+    while j < len(tokens):
+        if tokens[j].type in (tokenize.NL, tokenize.NEWLINE):
+            j += 1
+            continue
+
+        if tokens[j].start[1] < indention_level:
+            return 2
+
+        break
+
     return 1
 
 
@@ -379,7 +390,10 @@ def _get_newlines_by_type(
     int
         The number of newlines to insert after the docstring.
     """
-    if _classify.is_module_docstring(tokens, index):
+    if _classify.is_docstring_at_end_of_file(tokens, index):
+        # print("End of file")
+        return 0
+    elif _classify.is_module_docstring(tokens, index):
         # print("Module")
         return _get_module_docstring_newlines(black)
     elif _classify.is_class_docstring(tokens, index):

tests/_data/string_files/do_format_code.toml

@@ -42,7 +42,6 @@ source='''
 expected='''
     CONST = 123
     """Docstring for CONST."""
-
 '''
 
 [class_docstring]
@@ -60,7 +59,6 @@ expected='''
         :cvar test_int: a class attribute.
         .. py:method:: big_method()
         """
-
 '''
 
 [newline_class_variable]
@@ -87,7 +85,6 @@ expected='''
 
         test_var2 = 1
         """This is a second class variable docstring."""
-
 '''
 
 [class_attribute_wrap]
@@ -102,7 +99,6 @@ expected='''class TestClass:
     test_int = 1
     """This is a very, very, very long docstring that should really be
     reformatted nicely by docformatter."""
-
 '''
 
 [newline_outside_docstring]
@@ -364,7 +360,6 @@ expected='''class Foo:
 
     More stuff.
     """
-
 '''
 
 [class_empty_lines_2]
@@ -688,7 +683,6 @@ class TestClass:
     :cvar test_int: a class attribute.
     ..py:method:: big_method()
     """
-
 '''
 
 [issue_139_2]
@@ -1134,7 +1128,6 @@ expected='''
 #!/usr/bin/env python
 
 """a.py."""
-
 '''
 
 [issue_203]
@@ -1167,3 +1160,76 @@ expected='''def foo(bar):
     Description.
     """
 '''
+
+[two_lines_between_stub_classes]
+source='''class Foo:
+    """Foo class."""
+class Bar:
+    """Bar class."""
+'''
+expected='''class Foo:
+    """Foo class."""
+
+
+class Bar:
+    """Bar class."""
+'''
+
+[two_lines_between_stub_classes_with_preceding_comment]
+source='''class Foo:
+    """Foo class."""
+
+# A comment for class Bar
+class Bar:
+    """Bar class."""
+'''
+expected='''class Foo:
+    """Foo class."""
+
+
+# A comment for class Bar
+class Bar:
+    """Bar class."""
+'''
+
+[ellipses_is_code_line]
+source='''class Foo:
+    def bar() -> str:
+        """Bar."""
+
+        ...
+
+    def baz() -> None:
+        """Baz."""
+
+        ...
+'''
+expected='''class Foo:
+    def bar() -> str:
+        """Bar."""
+        ...
+
+    def baz() -> None:
+        """Baz."""
+        ...
+'''
+
+[do_not_break_f_string_double_quotes]
+source='''foo = f"""
+  bar
+"""
+'''
+expected='''foo = f"""
+  bar
+"""
+'''
+
+[do_not_break_f_string_single_quotes]
+source="""foo = f'''
+  bar
+'''
+"""
+expected="""foo = f'''
+  bar
+'''
+"""

tests/_data/string_files/format_functions.toml

@@ -169,11 +169,11 @@ expected = 1
 
 [get_newlines_by_type_module_docstring]
 source = '"""Module docstring."""'
-expected = 1
+expected = 0
 
 [get_newlines_by_type_module_docstring_black]
 source = '"""Module docstring."""'
-expected = 2
+expected = 0
 
 [get_newlines_by_type_class_docstring]
 source = '''
@@ -195,7 +195,7 @@ expected = 0
 source = '''x = 1
 """Docstring for x."""
 '''
-expected = 1
+expected = 0
 
 [get_num_rows_columns]
 token = [5, "    ", [3, 10], [3, 40], '''    This is

tests/formatter/test_do_format_code.py

@@ -135,6 +135,11 @@
         ("issue_187", NO_ARGS),
         ("issue_203", NO_ARGS),
         ("issue_243", NO_ARGS),
+        ("two_lines_between_stub_classes", NO_ARGS),
+        ("two_lines_between_stub_classes_with_preceding_comment", NO_ARGS),
+        ("ellipses_is_code_line", NO_ARGS),
+        ("do_not_break_f_string_double_quotes", NO_ARGS),
+        ("do_not_break_f_string_single_quotes", NO_ARGS),
     ],
 )
 def test_do_format_code(test_key, test_args, args):