Add a --use-tabs argument to use tabs instead of spaces

Closes #47, psf#513, psf#640, psf#2122, psf#2584, psf#2798, psf#3349

src/black/__init__.py

@@ -282,6 +282,13 @@ def validate_regex(
         " functionality in the next major release."
     ),
 )
+@click.option(
+    "--use-tabs",
+    is_flag=True,
+    help=(
+        "Use tabs instead of spaces for indentation. Tabs are always equal to 4 spaces."
+    ),
+)
 @click.option(
     "--check",
     is_flag=True,
@@ -441,6 +448,7 @@ def main(  # noqa: C901
     skip_magic_trailing_comma: bool,
     experimental_string_processing: bool,
     preview: bool,
+    use_tabs: bool,
     quiet: bool,
     verbose: bool,
     required_version: Optional[str],
@@ -552,6 +560,7 @@ def main(  # noqa: C901
         experimental_string_processing=experimental_string_processing,
         preview=preview,
         python_cell_magics=set(python_cell_magics),
+        use_tabs=use_tabs,
     )
 
     if code is not None:

src/black/linegen.py

@@ -409,10 +409,11 @@ def visit_STRING(self, leaf: Leaf) -> Iterator[Line]:
             quote_len = 1 if docstring[1] != quote_char else 3
             docstring = docstring[quote_len:-quote_len]
             docstring_started_empty = not docstring
-            indent = " " * 4 * self.current_line.depth
+            indent_style = " " * 4 if not self.mode.use_tabs else "\t"
+            indent = indent_style * self.current_line.depth
 
             if is_multiline_string(leaf):
-                docstring = fix_docstring(docstring, indent)
+                docstring = fix_docstring(docstring, indent, not self.mode.use_tabs)
             else:
                 docstring = docstring.strip()
 

src/black/lines.py

@@ -456,11 +456,15 @@ def clone(self) -> "Line":
         )
 
     def __str__(self) -> str:
+        return self.render()
+
+    def render(self, force_spaces: bool = False) -> str:
         """Render the line."""
         if not self:
             return "\n"
 
-        indent = "    " * self.depth
+        indent_style = "    " if force_spaces or not self.mode.use_tabs else "\t"
+        indent = indent_style * self.depth
         leaves = iter(self.leaves)
         first = next(leaves)
         res = f"{first.prefix}{indent}{first.value}"
@@ -759,6 +763,8 @@ def is_line_short_enough(  # noqa: C901
     """
     if not line_str:
         line_str = line_to_string(line)
+    else:
+        line_str = line_str.expandtabs(tabsize=4)
 
     width = str_width if mode.preview else len
 
@@ -1002,9 +1008,9 @@ def _can_omit_closing_paren(line: Line, *, last: Leaf, line_length: int) -> bool
     return False
 
 
-def line_to_string(line: Line) -> str:
+def line_to_string(line: Line, force_spaces: bool = False) -> str:
     """Returns the string representation of @line.
 
     WARNING: This is known to be computationally expensive.
     """
-    return str(line).strip("\n")
+    return line.render(force_spaces=force_spaces).strip("\n")

src/black/mode.py

@@ -184,6 +184,7 @@ class Mode:
     experimental_string_processing: bool = False
     python_cell_magics: Set[str] = field(default_factory=set)
     preview: bool = False
+    use_tabs: bool = False
 
     def __post_init__(self) -> None:
         if self.experimental_string_processing:
@@ -225,5 +226,6 @@ def get_cache_key(self) -> str:
             str(int(self.experimental_string_processing)),
             str(int(self.preview)),
             sha256((",".join(sorted(self.python_cell_magics))).encode()).hexdigest(),
+            str(int(self.use_tabs)),
         ]
         return ".".join(parts)

src/black/strings.py

@@ -72,11 +72,14 @@ def lines_with_leading_tabs_expanded(s: str) -> List[str]:
     return lines
 
 
-def fix_docstring(docstring: str, prefix: str) -> str:
+def fix_docstring(docstring: str, prefix: str, expand_leading_tabs: bool) -> str:
     # https://www.python.org/dev/peps/pep-0257/#handling-docstring-indentation
     if not docstring:
         return ""
-    lines = lines_with_leading_tabs_expanded(docstring)
+    if expand_leading_tabs:
+        lines = lines_with_leading_tabs_expanded(docstring)
+    else:
+        lines = docstring.splitlines()
     # Determine minimum indentation (first line doesn't count):
     indent = sys.maxsize
     for line in lines[1:]:

tests/data/tabs/docstring_tabs.py

@@ -0,0 +1,276 @@
+class MyClass:
+  """ Multiline
+  class docstring
+  """
+
+  def method(self):
+    """Multiline
+    method docstring
+    """
+    pass
+
+
+def foo():
+  """This is a docstring with             
+  some lines of text here
+  """
+  return
+
+
+def bar():
+  '''This is another docstring
+  with more lines of text
+  '''
+  return
+
+
+def baz():
+  '''"This" is a string with some
+  embedded "quotes"'''
+  return
+
+
+def troz():
+	'''Indentation with tabs
+	is just as OK
+	'''
+	return
+
+
+def zort():
+        """Another
+        multiline
+        docstring
+        """
+        pass
+
+def poit():
+  """
+  Lorem ipsum dolor sit amet.       
+
+  Consectetur adipiscing elit:
+   - sed do eiusmod tempor incididunt ut labore
+   - dolore magna aliqua
+     - enim ad minim veniam
+     - quis nostrud exercitation ullamco laboris nisi
+   - aliquip ex ea commodo consequat
+  """
+  pass
+
+
+def under_indent():
+  """
+  These lines are indented in a way that does not
+make sense.
+  """
+  pass
+
+
+def over_indent():
+  """
+  This has a shallow indent
+    - But some lines are deeper
+    - And the closing quote is too deep
+    """
+  pass
+
+
+def single_line():
+    """But with a newline after it!
+
+    """
+    pass
+
+
+def this():
+    r"""
+    'hey ho'
+    """
+
+
+def that():
+  """ "hey yah" """
+
+
+def and_that():
+  """
+  "hey yah" """
+
+
+def and_this():
+  ''' 
+  "hey yah"'''
+
+
+def believe_it_or_not_this_is_in_the_py_stdlib(): ''' 
+"hey yah"'''
+
+
+def ignored_docstring():
+    """a => \
+b"""  
+
+
+def docstring_with_inline_tabs_and_space_indentation():
+    """hey
+
+    tab	separated	value
+    	tab at start of line and then a tab	separated	value
+    				multiple tabs at the beginning	and	inline
+    	 	  	mixed tabs and spaces at beginning. next line has mixed tabs and spaces only.
+    			 	  		
+    line ends with some tabs		
+    """
+
+
+def docstring_with_inline_tabs_and_tab_indentation():
+	"""hey
+
+	tab	separated	value
+		tab at start of line and then a tab	separated	value
+					multiple tabs at the beginning	and	inline
+		 	  	mixed tabs and spaces at beginning. next line has mixed tabs and spaces only.
+				 	  		
+	line ends with some tabs		
+	"""
+	pass
+
+
+# output
+
+class MyClass:
+	"""Multiline
+	class docstring
+	"""
+
+	def method(self):
+		"""Multiline
+		method docstring
+		"""
+		pass
+
+
+def foo():
+	"""This is a docstring with
+	some lines of text here
+	"""
+	return
+
+
+def bar():
+	"""This is another docstring
+	with more lines of text
+	"""
+	return
+
+
+def baz():
+	'''"This" is a string with some
+	embedded "quotes"'''
+	return
+
+
+def troz():
+	"""Indentation with tabs
+	is just as OK
+	"""
+	return
+
+
+def zort():
+	"""Another
+	multiline
+	docstring
+	"""
+	pass
+
+
+def poit():
+	"""
+	Lorem ipsum dolor sit amet.
+
+	Consectetur adipiscing elit:
+	 - sed do eiusmod tempor incididunt ut labore
+	 - dolore magna aliqua
+	   - enim ad minim veniam
+	   - quis nostrud exercitation ullamco laboris nisi
+	 - aliquip ex ea commodo consequat
+	"""
+	pass
+
+
+def under_indent():
+	"""
+	  These lines are indented in a way that does not
+	make sense.
+	"""
+	pass
+
+
+def over_indent():
+	"""
+	This has a shallow indent
+	  - But some lines are deeper
+	  - And the closing quote is too deep
+	"""
+	pass
+
+
+def single_line():
+	"""But with a newline after it!"""
+	pass
+
+
+def this():
+	r"""
+	'hey ho'
+	"""
+
+
+def that():
+	""" "hey yah" """
+
+
+def and_that():
+	"""
+	"hey yah" """
+
+
+def and_this():
+	'''
+	"hey yah"'''
+
+
+def believe_it_or_not_this_is_in_the_py_stdlib():
+	'''
+	"hey yah"'''
+
+
+def ignored_docstring():
+	"""a => \
+b"""
+
+
+def docstring_with_inline_tabs_and_space_indentation():
+	"""hey
+
+	tab	separated	value
+		tab at start of line and then a tab	separated	value
+					multiple tabs at the beginning	and	inline
+		 	  	mixed tabs and spaces at beginning. next line has mixed tabs and spaces only.
+
+	line ends with some tabs
+	"""
+
+
+def docstring_with_inline_tabs_and_tab_indentation():
+	"""hey
+
+	tab	separated	value
+		tab at start of line and then a tab	separated	value
+					multiple tabs at the beginning	and	inline
+		 	  	mixed tabs and spaces at beginning. next line has mixed tabs and spaces only.
+
+	line ends with some tabs
+	"""
+	pass