Python docstring whitespace strip for single lines

Python does not consistently handle whitespace stripping of
contents in __doc__ across different versions and interfaces.
For example python-3.13 heap types don't strip whitespace
but but static types do. Python-3.12 and earlier didn't strip
any whitespace either. inspect.getdoc() does consistently remove
docstrings though. Given the whitespace is pointless, SWIG now
strips this off for single line docstrings.

Examples/test-suite/python/python_docstring_runme.py

@@ -87,16 +87,21 @@ check(inspect.getdoc(DocStrings.docstringC),
     "second line"
     )
 
-# One line doc special case, use __doc__
-if sys.version_info[0:2] < (3, 13):
-    check(DocStrings.docstringX.__doc__, "  one line docs")
-else:
-    check(DocStrings.docstringX.__doc__, "one line docs")
+# One line doc special case, use __doc__ to check for stripped whitespace
+check(DocStrings.docstringW.__doc__, "one line docs")
+check(DocStrings.docstringX.__doc__, "one line docs leading whitespace")
+check(DocStrings.docstringY.__doc__, "one line docs trailing whitespace")
+check(DocStrings.docstringZ.__doc__, "one line docs whitespace")
 
+check(inspect.getdoc(DocStrings.docstringW),
+    "one line docs"
+    )
 check(inspect.getdoc(DocStrings.docstringX),
-    "one line docs"
+    "one line docs leading whitespace"
     )
-
 check(inspect.getdoc(DocStrings.docstringY),
-    "one line docs"
+    "one line docs trailing whitespace"
+    )
+check(inspect.getdoc(DocStrings.docstringZ),
+    "one line docs whitespace"
     )

Examples/test-suite/python_docstring.i

@@ -77,8 +77,10 @@ line 3
 %{  first line
   second line%}
 
-%feature("docstring") docstringX "  one line docs"
-%feature("docstring") docstringY "one line docs"
+%feature("docstring") docstringW "one line docs"
+%feature("docstring") docstringX "  one line docs leading whitespace"
+%feature("docstring") docstringY "one line docs trailing whitespace\t  "
+%feature("docstring") docstringZ "\tone line docs whitespace  \t"
 
 %inline %{
 struct DocStrings {
@@ -92,7 +94,9 @@ struct DocStrings {
   void docstringA() {}
   void docstringB() {}
   void docstringC() {}
+  void docstringW() {}
   void docstringX() {}
   void docstringY() {}
+  void docstringZ() {}
 };
 %}

Source/Modules/python.cxx

@@ -1614,6 +1614,17 @@ public:
       Append(tmp, indent);
       Delete(docstr);
       docstr = tmp;
+    } else {
+      // Removing leading and trailing whitespace for single line docstrings
+      Chop(docstr);
+      const char *c = Char(docstr);
+      if (isspace((int)*c)) {
+	while(isspace((int)*(++c))) {
+	}
+	String *old_docstr = docstr;
+	docstr = NewString(c);
+	Delete(old_docstr);
+      }
     }
 
     return docstr;