Fix crash on empty summary line with no whitespace option (#161)

Co-authored-by: Daniël van Noord <13665637+DanielNoord@users.noreply.github.com>

Author: jspaezp

.pre-commit-config.yaml

@@ -3,7 +3,7 @@ repos:
     rev: v4.3.0
     hooks:
       - id: trailing-whitespace
-        exclude: "tests/data/format/whitespace_stripper|tests/data/format/quotes_type|tests/data/format/newlines|tests/test_config.py"
+        exclude: "tests/data/format/no_whitespace_stripper|tests/data/format/whitespace_stripper|tests/data/format/quotes_type|tests/data/format/newlines|tests/test_config.py"
       - id: end-of-file-fixer
         exclude: "tests/data/format/newlines"
       - id: check-yaml

pydocstringformatter/_formatting/_utils.py

@@ -5,5 +5,6 @@
 def is_rst_title(summary: str) -> bool:
     """Check if the second line of a summary is one recurring character."""
     # If second line is one recurring character we're dealing with a rst title
-    last_line = summary.splitlines()[-1].lstrip()
+    if not (last_line := summary.splitlines()[-1].lstrip()):
+        return False
     return last_line.count(last_line[0]) == len(last_line)

tests/data/format/no_whitespace_stripper/module_docstring.args

@@ -0,0 +1 @@
+--no-strip-whitespaces

tests/data/format/no_whitespace_stripper/module_docstring.py

@@ -0,0 +1,12 @@
+"""  A multi-line  
+docstring  
+"""
+
+"""  A multi-line  
+docstring  
+   """
+
+"""  My docstring.  
+    
+   My indented section  
+  """

tests/data/format/no_whitespace_stripper/module_docstring.py.out

@@ -0,0 +1,18 @@
+"""  A multi-line  .
+
+docstring  
+"""
+
+"""  A multi-line  .
+
+docstring  
+   
+"""
+
+"""  My docstring.
+
+ 
+    
+   My indented section  
+  
+"""