Issue #27985: Implement PEP 526 -- Syntax for Variable Annotations.

Patch by Ivan Levkivskyi.

Lib/test/test_grammar.py

@@ -8,6 +8,14 @@ import sys
 # testing import *
 from sys import *
 
+# different import patterns to check that __annotations__ does not interfere
+# with import machinery
+import test.ann_module as ann_module
+import typing
+from collections import ChainMap
+from test import ann_module2
+import test
+
 
 class TokenTests(unittest.TestCase):
 
@@ -139,6 +147,19 @@ the \'lazy\' dog.\n\
                 compile(s, "<test>", "exec")
             self.assertIn("unexpected EOF", str(cm.exception))
 
+var_annot_global: int # a global annotated is necessary for test_var_annot
+
+# custom namespace for testing __annotations__
+
+class CNS:
+    def __init__(self):
+        self._dct = {}
+    def __setitem__(self, item, value):
+        self._dct[item.lower()] = value
+    def __getitem__(self, item):
+        return self._dct[item]
+
+
 class GrammarTests(unittest.TestCase):
 
     # single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
@@ -154,6 +175,163 @@ class GrammarTests(unittest.TestCase):
         # testlist ENDMARKER
         x = eval('1, 0 or 1')
 
+    def test_var_annot_basics(self):
+        # all these should be allowed
+        var1: int = 5
+        var2: [int, str]
+        my_lst = [42]
+        def one():
+            return 1
+        int.new_attr: int
+        [list][0]: type
+        my_lst[one()-1]: int = 5
+        self.assertEqual(my_lst, [5])
+
+    def test_var_annot_syntax_errors(self):
+        # parser pass
+        check_syntax_error(self, "def f: int")
+        check_syntax_error(self, "x: int: str")
+        check_syntax_error(self, "def f():\n"
+                                 "    nonlocal x: int\n")
+        # AST pass
+        check_syntax_error(self, "[x, 0]: int\n")
+        check_syntax_error(self, "f(): int\n")
+        check_syntax_error(self, "(x,): int")
+        check_syntax_error(self, "def f():\n"
+                                 "    (x, y): int = (1, 2)\n")
+        # symtable pass
+        check_syntax_error(self, "def f():\n"
+                                 "    x: int\n"
+                                 "    global x\n")
+        check_syntax_error(self, "def f():\n"
+                                 "    global x\n"
+                                 "    x: int\n")
+
+    def test_var_annot_basic_semantics(self):
+        # execution order
+        with self.assertRaises(ZeroDivisionError):
+            no_name[does_not_exist]: no_name_again = 1/0
+        with self.assertRaises(NameError):
+            no_name[does_not_exist]: 1/0 = 0
+        global var_annot_global
+
+        # function semantics
+        def f():
+            st: str = "Hello"
+            a.b: int = (1, 2)
+            return st
+        self.assertEqual(f.__annotations__, {})
+        def f_OK():
+            x: 1/0
+        f_OK()
+        def fbad():
+            x: int
+            print(x)
+        with self.assertRaises(UnboundLocalError):
+            fbad()
+        def f2bad():
+            (no_such_global): int
+            print(no_such_global)
+        try:
+            f2bad()
+        except Exception as e:
+            self.assertIs(type(e), NameError)
+
+        # class semantics
+        class C:
+            x: int
+            s: str = "attr"
+            z = 2
+            def __init__(self, x):
+                self.x: int = x
+        self.assertEqual(C.__annotations__, {'x': int, 's': str})
+        with self.assertRaises(NameError):
+            class CBad:
+                no_such_name_defined.attr: int = 0
+        with self.assertRaises(NameError):
+            class Cbad2(C):
+                x: int
+                x.y: list = []
+
+    def test_var_annot_metaclass_semantics(self):
+        class CMeta(type):
+            @classmethod
+            def __prepare__(metacls, name, bases, **kwds):
+                return {'__annotations__': CNS()}
+        class CC(metaclass=CMeta):
+            XX: 'ANNOT'
+        self.assertEqual(CC.__annotations__['xx'], 'ANNOT')
+
+    def test_var_annot_module_semantics(self):
+        with self.assertRaises(AttributeError):
+            print(test.__annotations__)
+        self.assertEqual(ann_module.__annotations__,
+                     {1: 2, 'x': int, 'y': str, 'f': typing.Tuple[int, int]})
+        self.assertEqual(ann_module.M.__annotations__,
+                              {'123': 123, 'o': type})
+        self.assertEqual(ann_module2.__annotations__, {})
+        self.assertEqual(typing.get_type_hints(ann_module2.CV,
+                                               ann_module2.__dict__),
+                         ChainMap({'var': typing.ClassVar[ann_module2.CV]}, {}))
+
+    def test_var_annot_in_module(self):
+        # check that functions fail the same way when executed
+        # outside of module where they were defined
+        from test.ann_module3 import f_bad_ann, g_bad_ann, D_bad_ann
+        with self.assertRaises(NameError):
+            f_bad_ann()
+        with self.assertRaises(NameError):
+            g_bad_ann()
+        with self.assertRaises(NameError):
+            D_bad_ann(5)
+
+    def test_var_annot_simple_exec(self):
+        gns = {}; lns= {}
+        exec("'docstring'\n"
+             "__annotations__[1] = 2\n"
+             "x: int = 5\n", gns, lns)
+        self.assertEqual(lns["__annotations__"], {1: 2, 'x': int})
+        with self.assertRaises(KeyError):
+            gns['__annotations__']
+
+    def test_var_annot_custom_maps(self):
+        # tests with custom locals() and __annotations__
+        ns = {'__annotations__': CNS()}
+        exec('X: int; Z: str = "Z"; (w): complex = 1j', ns)
+        self.assertEqual(ns['__annotations__']['x'], int)
+        self.assertEqual(ns['__annotations__']['z'], str)
+        with self.assertRaises(KeyError):
+            ns['__annotations__']['w']
+        nonloc_ns = {}
+        class CNS2:
+            def __init__(self):
+                self._dct = {}
+            def __setitem__(self, item, value):
+                nonlocal nonloc_ns
+                self._dct[item] = value
+                nonloc_ns[item] = value
+            def __getitem__(self, item):
+                return self._dct[item]
+        exec('x: int = 1', {}, CNS2())
+        self.assertEqual(nonloc_ns['__annotations__']['x'], int)
+
+    def test_var_annot_refleak(self):
+        # complex case: custom locals plus custom __annotations__
+        # this was causing refleak
+        cns = CNS()
+        nonloc_ns = {'__annotations__': cns}
+        class CNS2:
+            def __init__(self):
+                self._dct = {'__annotations__': cns}
+            def __setitem__(self, item, value):
+                nonlocal nonloc_ns
+                self._dct[item] = value
+                nonloc_ns[item] = value
+            def __getitem__(self, item):
+                return self._dct[item]
+        exec('X: str', {}, CNS2())
+        self.assertEqual(nonloc_ns['__annotations__']['x'], str)
+
     def test_funcdef(self):
         ### [decorators] 'def' NAME parameters ['->' test] ':' suite
         ### decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE