Make black remove leading and trailing spaces from one-line docstrings: fixes #1738 #1812

CHANGES.md

@@ -4,6 +4,9 @@
 
 #### _Black_
 
+- `Black` now processes one-line docstrings by stripping leading and trailing spaces,
+  and adding a padding space when needed to break up """". (#1740)
+
 - `Black` now cleans up leading non-breaking spaces in comments (#2092)
 
 - `Black` now respects `--skip-string-normalization` when normalizing multiline

src/black/__init__.py

@@ -2153,16 +2153,35 @@ def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
             # We're ignoring docstrings with backslash newline escapes because changing
             # indentation of those changes the AST representation of the code.
             prefix = get_string_prefix(leaf.value)
-            lead_len = len(prefix) + 3
-            tail_len = -3
-            indent = " " * 4 * self.current_line.depth
-            docstring = fix_docstring(leaf.value[lead_len:tail_len], indent)
+            docstring = leaf.value[len(prefix) :]  # Remove the prefix
+            quote_char = docstring[0]
+            # A natural way to remove the outer quotes is to do:
+            #   docstring = docstring.strip(quote_char)
+            # but that breaks on """""x""" (which is '""x').
+            # So we actually need to remove the first character and the next two
+            # characters but only if they are the same as the first.
+            quote_len = 1 if docstring[1] != quote_char else 3
+            docstring = docstring[quote_len:-quote_len]
+
+            if is_multiline_string(leaf):
+                indent = " " * 4 * self.current_line.depth
+                docstring = fix_docstring(docstring, indent)
+            else:
+                docstring = docstring.strip()
+
             if docstring:
-                if leaf.value[lead_len - 1] == docstring[0]:
+                # Add some padding if the docstring starts / ends with a quote mark.
+                if docstring[0] == quote_char:
                     docstring = " " + docstring
-                if leaf.value[tail_len + 1] == docstring[-1]:
+                if docstring[-1] == quote_char:
                     docstring = docstring + " "
-            leaf.value = leaf.value[0:lead_len] + docstring + leaf.value[tail_len:]
+            else:
+                # Add some padding if the docstring is empty.
+                docstring = " "
+
+            # We could enforce triple quotes at this point.
+            quote = quote_char * quote_len
+            leaf.value = prefix + quote + docstring + quote
 
         yield from self.visit_default(leaf)
 
@@ -6113,7 +6132,7 @@ def get_imports_from_children(children: List[LN]) -> Generator[str, None, None]:
 
 @lru_cache()
 def get_gitignore(root: Path) -> PathSpec:
-    """ Return a PathSpec matching gitignore content if present."""
+    """Return a PathSpec matching gitignore content if present."""
     gitignore = root / ".gitignore"
     lines: List[str] = []
     if gitignore.is_file():
@@ -6953,11 +6972,6 @@ def patched_main() -> None:
 
 
 def is_docstring(leaf: Leaf) -> bool:
-    if not is_multiline_string(leaf):
-        # For the purposes of docstring re-indentation, we don't need to do anything
-        # with single-line docstrings.
-        return False
-
     if prev_siblings_are(
         leaf.parent, [None, token.NEWLINE, token.INDENT, syms.simple_stmt]
     ):

src/black_primer/primer.json

@@ -3,7 +3,7 @@
   "projects": {
     "aioexabgp": {
       "cli_arguments": [],
-      "expect_formatting_changes": false,
+      "expect_formatting_changes": true,
       "git_clone_url": "https://github.com/cooperlees/aioexabgp.git",
       "long_checkout": false,
       "py_versions": ["all"]
@@ -17,7 +17,7 @@
     },
     "bandersnatch": {
       "cli_arguments": [],
-      "expect_formatting_changes": false,
+      "expect_formatting_changes": true,
       "git_clone_url": "https://github.com/pypa/bandersnatch.git",
       "long_checkout": false,
       "py_versions": ["all"]
@@ -84,7 +84,7 @@
     },
     "ptr": {
       "cli_arguments": [],
-      "expect_formatting_changes": false,
+      "expect_formatting_changes": true,
       "git_clone_url": "https://github.com/facebookincubator/ptr.git",
       "long_checkout": false,
       "py_versions": ["all"]
@@ -98,14 +98,14 @@
     },
     "sqlalchemy": {
       "cli_arguments": [],
-      "expect_formatting_changes": false,
+      "expect_formatting_changes": true,
       "git_clone_url": "https://github.com/sqlalchemy/sqlalchemy.git",
       "long_checkout": false,
       "py_versions": ["all"]
     },
     "tox": {
       "cli_arguments": [],
-      "expect_formatting_changes": false,
+      "expect_formatting_changes": true,
       "git_clone_url": "https://github.com/tox-dev/tox.git",
       "long_checkout": false,
       "py_versions": ["all"]

tests/data/docstring.py

@@ -102,6 +102,23 @@ def and_this():
   "hey yah"'''
 
 
+def empty():
+    '''
+
+
+
+
+    '''
+
+
+def oneline_empty():
+    '''      '''
+
+
+def single_quotes():
+    'testing'
+
+
 def believe_it_or_not_this_is_in_the_py_stdlib(): ''' 
 "hey yah"'''
 
@@ -110,6 +127,8 @@ def ignored_docstring():
     """a => \
 b"""  
 
+def single_line_docstring_with_whitespace():
+    """   This should be stripped """
 
 def docstring_with_inline_tabs_and_space_indentation():
     """hey
@@ -134,7 +153,6 @@ def docstring_with_inline_tabs_and_tab_indentation():
 	line ends with some tabs		
 	"""
 	pass
-
 
 # output
 
@@ -241,6 +259,18 @@ def and_this():
     "hey yah"'''
 
 
+def empty():
+    """ """
+
+
+def oneline_empty():
+    """ """
+
+
+def single_quotes():
+    "testing"
+
+
 def believe_it_or_not_this_is_in_the_py_stdlib():
     '''
     "hey yah"'''
@@ -251,6 +281,10 @@ def ignored_docstring():
 b"""
 
 
+def single_line_docstring_with_whitespace():
+    """This should be stripped"""
+
+
 def docstring_with_inline_tabs_and_space_indentation():
     """hey
 

tox.ini

@@ -23,4 +23,4 @@ commands =
     pip install -e .[d]
     coverage erase
     coverage run fuzz.py
-    coverage report
+    coverage report