bpo-32911: Revert bpo-29463. (GH-7121) (GH-7197)

Remove the docstring attribute of AST types and restore docstring expression as a first stmt in their body. Co-authored-by: INADA Naoki <methane@users.noreply.github.com>

Author: serhiy-storchaka

Doc/library/ast.rst

@@ -151,10 +151,6 @@ and classes for traversing abstract syntax trees:
  .. versionchanged:: 3.5
  :class:`AsyncFunctionDef` is now supported.
 
- .. versionchanged:: 3.7
- The docstring is now exported from the node docstring field, instead of
- the first body statement.
-
 
 .. function:: fix_missing_locations(node)
 

Doc/whatsnew/3.7.rst

@@ -2161,13 +2161,6 @@ Changes in Python Behavior
 Changes in the Python API
 -------------------------
 
-* ``Module``, ``FunctionDef``, ``AsyncFunctionDef``, and
- ``ClassDef`` AST nodes now have the new ``docstring`` attribute.
- The first statement in their body is not considered as a docstring
- anymore. ``co_firstlineno`` and ``co_lnotab`` of code object for class
- and module are affected by this change. (Contributed by INADA Naoki and
- Eugene Toder in :issue:`29463`.)
-
 * :meth:`socketserver.ThreadingMixIn.server_close` now waits until all
  non-daemon threads complete. Set the new
  :attr:`socketserver.ThreadingMixIn.block_on_close` class attribute to

Include/Python-ast.h

@@ -46,7 +46,6 @@ struct _mod {
  union {
  struct {
  asdl_seq *body;
- string docstring;
  } Module;
 
  struct {
@@ -81,7 +80,6 @@ struct _stmt {
  asdl_seq *body;
  asdl_seq *decorator_list;
  expr_ty returns;
- string docstring;
  } FunctionDef;
 
  struct {
@@ -90,7 +88,6 @@ struct _stmt {
  asdl_seq *body;
  asdl_seq *decorator_list;
  expr_ty returns;
- string docstring;
  } AsyncFunctionDef;
 
  struct {
@@ -99,7 +96,6 @@ struct _stmt {
  asdl_seq *keywords;
  asdl_seq *body;
  asdl_seq *decorator_list;
- string docstring;
  } ClassDef;
 
  struct {
@@ -443,27 +439,26 @@ struct _withitem {
 };
 
 
-#define Module(a0, a1, a2) _Py_Module(a0, a1, a2)
-mod_ty _Py_Module(asdl_seq * body, string docstring, PyArena *arena);
+#define Module(a0, a1) _Py_Module(a0, a1)
+mod_ty _Py_Module(asdl_seq * body, PyArena *arena);
 #define Interactive(a0, a1) _Py_Interactive(a0, a1)
 mod_ty _Py_Interactive(asdl_seq * body, PyArena *arena);
 #define Expression(a0, a1) _Py_Expression(a0, a1)
 mod_ty _Py_Expression(expr_ty body, PyArena *arena);
 #define Suite(a0, a1) _Py_Suite(a0, a1)
 mod_ty _Py_Suite(asdl_seq * body, PyArena *arena);
-#define FunctionDef(a0, a1, a2, a3, a4, a5, a6, a7, a8) _Py_FunctionDef(a0, a1, a2, a3, a4, a5, a6, a7, a8)
+#define FunctionDef(a0, a1, a2, a3, a4, a5, a6, a7) _Py_FunctionDef(a0, a1, a2, a3, a4, a5, a6, a7)
 stmt_ty _Py_FunctionDef(identifier name, arguments_ty args, asdl_seq * body,
- asdl_seq * decorator_list, expr_ty returns, string
- docstring, int lineno, int col_offset, PyArena *arena);
-#define AsyncFunctionDef(a0, a1, a2, a3, a4, a5, a6, a7, a8) _Py_AsyncFunctionDef(a0, a1, a2, a3, a4, a5, a6, a7, a8)
+ asdl_seq * decorator_list, expr_ty returns, int lineno,
+ int col_offset, PyArena *arena);
+#define AsyncFunctionDef(a0, a1, a2, a3, a4, a5, a6, a7) _Py_AsyncFunctionDef(a0, a1, a2, a3, a4, a5, a6, a7)
 stmt_ty _Py_AsyncFunctionDef(identifier name, arguments_ty args, asdl_seq *
  body, asdl_seq * decorator_list, expr_ty returns,
- string docstring, int lineno, int col_offset,
- PyArena *arena);
-#define ClassDef(a0, a1, a2, a3, a4, a5, a6, a7, a8) _Py_ClassDef(a0, a1, a2, a3, a4, a5, a6, a7, a8)
+ int lineno, int col_offset, PyArena *arena);
+#define ClassDef(a0, a1, a2, a3, a4, a5, a6, a7) _Py_ClassDef(a0, a1, a2, a3, a4, a5, a6, a7)
 stmt_ty _Py_ClassDef(identifier name, asdl_seq * bases, asdl_seq * keywords,
- asdl_seq * body, asdl_seq * decorator_list, string
- docstring, int lineno, int col_offset, PyArena *arena);
+ asdl_seq * body, asdl_seq * decorator_list, int lineno,
+ int col_offset, PyArena *arena);
 #define Return(a0, a1, a2, a3) _Py_Return(a0, a1, a2, a3)
 stmt_ty _Py_Return(expr_ty value, int lineno, int col_offset, PyArena *arena);
 #define Delete(a0, a1, a2, a3) _Py_Delete(a0, a1, a2, a3)

Lib/ast.py

@@ -206,7 +206,15 @@ def get_docstring(node, clean=True):
  """
  if not isinstance(node, (AsyncFunctionDef, FunctionDef, ClassDef, Module)):
  raise TypeError("%r can't have docstrings" % node.__class__.__name__)
- text = node.docstring
+ if not node.body:
+ return None
+ node = node.body[0].value
+ if isinstance(node, Str):
+ text = node.s
+ elif isinstance(node, Constant) and isinstance(node.value, str):
+ text = node.value
+ else:
+ return None
  if clean and text:
  import inspect
  text = inspect.cleandoc(text)