Add D419: Add and switch to "Docstring is empty" error code (#559)

Co-authored-by: Sambhav Kothari <sambhavs.email@gmail.com>

docs/release_notes.rst

@@ -12,6 +12,7 @@ New Features
 
 * Add support for `property_decorators` config to ignore D401.
 * Add support for Python 3.10 (#554).
+* Replace D10X errors with D419 if docstring exists but is empty (#559).
 
 6.1.1 - May 17th, 2021
 ---------------------------

src/pydocstyle/checker.py

@@ -196,12 +196,7 @@ def check_docstring_missing(self, definition, docstring):
               with a single underscore.
 
         """
-        if (
-            not docstring
-            and definition.is_public
-            or docstring
-            and is_blank(ast.literal_eval(docstring))
-        ):
+        if not docstring and definition.is_public:
             codes = {
                 Module: violations.D100,
                 Class: violations.D101,
@@ -227,6 +222,18 @@ def check_docstring_missing(self, definition, docstring):
             }
             return codes[type(definition)]()
 
+    @check_for(Definition, terminal=True)
+    def check_docstring_empty(self, definition, docstring):
+        """D419: Docstring is empty.
+
+        If the user provided a docstring but it was empty, it is like they never provided one.
+
+        NOTE: This used to report as D10X errors.
+
+        """
+        if docstring and is_blank(ast.literal_eval(docstring)):
+            return violations.D419()
+
     @check_for(Definition)
     def check_one_liners(self, definition, docstring):
         """D200: One-liner docstrings should fit on one line with quotes.

src/pydocstyle/violations.py

@@ -415,6 +415,10 @@ def to_rst(cls) -> str:
     'D418',
     'Function/ Method decorated with @overload shouldn\'t contain a docstring',
 )
+D419 = D4xx.create_error(
+    'D419',
+    'Docstring is empty',
+)
 
 
 class AttrDict(dict):

src/tests/test_cases/capitalization.py

@@ -13,7 +13,7 @@ def not_capitalized():
 
 
 # Make sure empty docstrings don't generate capitalization errors.
-@expect("D103: Missing docstring in public function")
+@expect("D419: Docstring is empty")
 def empty_docstring():
     """"""
 

src/tests/test_cases/test.py

@@ -13,7 +13,7 @@
 
 class class_:
 
-    expect('meta', 'D106: Missing docstring in public nested class')
+    expect('meta', 'D419: Docstring is empty')
 
     class meta:
         """"""
@@ -64,13 +64,13 @@ def __call__(self=None, x=None, y=None, z=None):
         pass
 
 
-@expect('D103: Missing docstring in public function')
+@expect('D419: Docstring is empty')
 def function():
     """ """
     def ok_since_nested():
         pass
 
-    @expect('D103: Missing docstring in public function')
+    @expect('D419: Docstring is empty')
     def nested():
         ''