bpo-42806: Fix ast locations of f-strings inside parentheses (GH-24067)

Grammar/python.gram

@@ -580,18 +580,23 @@ star_targets[expr_ty]:
     | a=star_target !',' { a }
     | a=star_target b=(',' c=star_target { c })* [','] {
         _Py_Tuple(CHECK(asdl_expr_seq*, _PyPegen_seq_insert_in_front(p, a, b)), Store, EXTRA) }
-star_targets_seq[asdl_expr_seq*]: a[asdl_expr_seq*]=','.star_target+ [','] { a }
+star_targets_list_seq[asdl_expr_seq*]: a[asdl_expr_seq*]=','.star_target+ [','] { a }
+star_targets_tuple_seq[asdl_expr_seq*]:
+    | a=star_target b=(',' c=star_target { c })+ [','] { (asdl_expr_seq*) _PyPegen_seq_insert_in_front(p, a, b) }
+    | a=star_target ',' { (asdl_expr_seq*) _PyPegen_singleton_seq(p, a) }
 star_target[expr_ty] (memo):
     | '*' a=(!'*' star_target) {
         _Py_Starred(CHECK(expr_ty, _PyPegen_set_expr_context(p, a, Store)), Store, EXTRA) }
+    | target_with_star_atom
+target_with_star_atom[expr_ty] (memo):
     | a=t_primary '.' b=NAME !t_lookahead { _Py_Attribute(a, b->v.Name.id, Store, EXTRA) }
     | a=t_primary '[' b=slices ']' !t_lookahead { _Py_Subscript(a, b, Store, EXTRA) }
     | star_atom
 star_atom[expr_ty]:
     | a=NAME { _PyPegen_set_expr_context(p, a, Store) }
-    | '(' a=star_target ')' { _PyPegen_set_expr_context(p, a, Store) }
+    | '(' a=target_with_star_atom ')' { _PyPegen_set_expr_context(p, a, Store) }
-    | '(' a=[star_targets_seq] ')' { _Py_Tuple(a, Store, EXTRA) }
+    | '(' a=[star_targets_tuple_seq] ')' { _Py_Tuple(a, Store, EXTRA) }
-    | '[' a=[star_targets_seq] ']' { _Py_List(a, Store, EXTRA) }
+    | '[' a=[star_targets_list_seq] ']' { _Py_List(a, Store, EXTRA) }
 
 single_target[expr_ty]:
     | single_subscript_attribute_target

Lib/random.py

@@ -96,6 +96,7 @@ LOG4 = _log(4.0)
 SG_MAGICCONST = 1.0 + _log(4.5)
 BPF = 53        # Number of bits in a float
 RECIP_BPF = 2 ** -BPF
+_ONE = 1
 
 
 class Random(_random.Random):
@@ -288,7 +289,7 @@ class Random(_random.Random):
 
     ## -------------------- integer methods  -------------------
 
-    def randrange(self, start, stop=None, step=1):
+    def randrange(self, start, stop=None, step=_ONE):
         """Choose a random item from range(start, stop[, step]).
 
         This fixes the problem with randint() which includes the
@@ -311,7 +312,12 @@ class Random(_random.Random):
                 _warn('randrange() will raise TypeError in the future',
                       DeprecationWarning, 2)
                 raise ValueError("non-integer arg 1 for randrange()")
+
         if stop is None:
+            # We don't check for "step != 1" because it hasn't been
+            # type checked and converted to an integer yet.
+            if step is not _ONE:
+                raise TypeError('Missing a non-None stop argument')
             if istart > 0:
                 return self._randbelow(istart)
             raise ValueError("empty range for randrange()")
@@ -345,9 +351,9 @@ class Random(_random.Random):
                       DeprecationWarning, 2)
                 raise ValueError("non-integer step for randrange()")
         width = istop - istart
-        if istep == 1 and width > 0:
-            return istart + self._randbelow(width)
         if istep == 1:
+            if width > 0:
+                return istart + self._randbelow(width)
             raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width))
 
         # Non-unit step argument supplied.
@@ -357,10 +363,8 @@ class Random(_random.Random):
             n = (width + istep + 1) // istep
         else:
             raise ValueError("zero step for randrange()")
-
         if n <= 0:
             raise ValueError("empty range for randrange()")
-
         return istart + istep * self._randbelow(n)
 
     def randint(self, a, b):

Lib/test/test_fstring.py

@@ -332,6 +332,59 @@ non-important content
         self.assertEqual(binop.left.col_offset, 4)
         self.assertEqual(binop.right.col_offset, 7)
 
+    def test_ast_line_numbers_with_parentheses(self):
+        expr = """
+x = (
+    f" {test(t)}"
+)"""
+        t = ast.parse(expr)
+        self.assertEqual(type(t), ast.Module)
+        self.assertEqual(len(t.body), 1)
+        # check the test(t) location
+        call = t.body[0].value.values[1].value
+        self.assertEqual(type(call), ast.Call)
+        self.assertEqual(call.lineno, 3)
+        self.assertEqual(call.end_lineno, 3)
+        self.assertEqual(call.col_offset, 8)
+        self.assertEqual(call.end_col_offset, 15)
+
+        expr = """
+x = (
+        'PERL_MM_OPT', (
+            f'wat'
+            f'some_string={f(x)} '
+            f'wat'
+        ),
+)
+"""
+        t = ast.parse(expr)
+        self.assertEqual(type(t), ast.Module)
+        self.assertEqual(len(t.body), 1)
+        # check the fstring
+        fstring = t.body[0].value.elts[1]
+        self.assertEqual(type(fstring), ast.JoinedStr)
+        self.assertEqual(len(fstring.values), 3)
+        wat1, middle, wat2 = fstring.values
+        # check the first wat
+        self.assertEqual(type(wat1), ast.Constant)
+        self.assertEqual(wat1.lineno, 4)
+        self.assertEqual(wat1.end_lineno, 6)
+        self.assertEqual(wat1.col_offset, 12)
+        self.assertEqual(wat1.end_col_offset, 18)
+        # check the call
+        call = middle.value
+        self.assertEqual(type(call), ast.Call)
+        self.assertEqual(call.lineno, 5)
+        self.assertEqual(call.end_lineno, 5)
+        self.assertEqual(call.col_offset, 27)
+        self.assertEqual(call.end_col_offset, 31)
+        # check the second wat
+        self.assertEqual(type(wat2), ast.Constant)
+        self.assertEqual(wat2.lineno, 4)
+        self.assertEqual(wat2.end_lineno, 6)
+        self.assertEqual(wat2.col_offset, 12)
+        self.assertEqual(wat2.end_col_offset, 18)
+
     def test_docstring(self):
         def f():
             f'''Not a docstring'''

Lib/test/test_random.py

@@ -562,6 +562,14 @@ class SystemRandom_TestBasicOps(TestBasicOps, unittest.TestCase):
             with self.assertRaises(ValueError):
                 randrange(10, 20, 1.5)
 
+    def test_randrange_step(self):
+        # bpo-42772: When stop is None, the step argument was being ignored.
+        randrange = self.gen.randrange
+        with self.assertRaises(TypeError):
+            randrange(1000, step=100)
+        with self.assertRaises(TypeError):
+            randrange(1000, None, step=100)
+
     def test_randbelow_logic(self, _log=log, int=int):
         # check bitcount transition points:  2**i and 2**(i+1)-1
         # show that: k = int(1.001 + _log(n, 2))

Lib/test/test_unpack_ex.py

@@ -346,6 +346,31 @@ Now some general starred expressions (all fail).
       ...
     SyntaxError: can't use starred expression here
 
+    >>> (*x),y = 1, 2 # doctest:+ELLIPSIS
+    Traceback (most recent call last):
+      ...
+    SyntaxError: can't use starred expression here
+
+    >>> (((*x))),y = 1, 2 # doctest:+ELLIPSIS
+    Traceback (most recent call last):
+      ...
+    SyntaxError: can't use starred expression here
+
+    >>> z,(*x),y = 1, 2, 4 # doctest:+ELLIPSIS
+    Traceback (most recent call last):
+      ...
+    SyntaxError: can't use starred expression here
+
+    >>> z,(*x) = 1, 2 # doctest:+ELLIPSIS
+    Traceback (most recent call last):
+      ...
+    SyntaxError: can't use starred expression here
+
+    >>> ((*x),y) = 1, 2 # doctest:+ELLIPSIS
+    Traceback (most recent call last):
+      ...
+    SyntaxError: can't use starred expression here
+
 Some size constraints (all fail.)
 
     >>> s = ", ".join("a%d" % i for i in range(1<<8)) + ", *rest = range(1<<8 + 1)"

Misc/NEWS.d/next/Core and Builtins/2020-12-31-20-58-22.bpo-40631.deRMCx.rst

@@ -0,0 +1,2 @@
+Fix regression where a single parenthesized starred expression was a valid
+assignment target.

Misc/NEWS.d/next/Core and Builtins/2021-01-03-00-20-38.bpo-42806.mLAobJ.rst

@@ -0,0 +1,2 @@
+Fix the column offsets for f-strings :mod:`ast` nodes surrounded by
+parentheses and for nodes that spawn multiple lines. Patch by Pablo Galindo.

Misc/NEWS.d/next/Library/2020-12-30-17-16-43.bpo-42772.Xe7WFV.rst

@@ -0,0 +1,2 @@
+randrange() now raises a TypeError when step is specified without a stop
+argument.  Formerly, it silently ignored the step argument.

Parser/string_parser.c

@@ -405,7 +405,7 @@ fstring_compile_expr(Parser *p, const char *expr_start, const char *expr_end,
     Parser *p2 = _PyPegen_Parser_New(tok, Py_fstring_input, p->flags, p->feature_version,
                                      NULL, p->arena);
     p2->starting_lineno = t->lineno + lines - 1;
-    p2->starting_col_offset = p->tok->first_lineno == p->tok->lineno ? t->col_offset + cols : cols;
+    p2->starting_col_offset = t->col_offset + cols;
 
     expr = _PyPegen_run_parser(p2);