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bpo-39702: Relax grammar restrictions on decorators (PEP 614) (GH-18570)

This commit is contained in:
Brandt Bucher 2020-03-03 14:25:44 -08:00 committed by GitHub
parent 116fd4af73
commit be501ca241
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GPG Key ID: 4AEE18F83AFDEB23
8 changed files with 534 additions and 537 deletions
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2
Grammar/Grammar
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@ -14,7 +14,7 @@ single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
file_input: (NEWLINE | stmt)* ENDMARKER
eval_input: testlist NEWLINE* ENDMARKER
decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
decorator: '@' namedexpr_test NEWLINE
decorators: decorator+
decorated: decorators (classdef | funcdef | async_funcdef)

1
Include/node.h
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@ -31,7 +31,6 @@ PyAPI_FUNC(Py_ssize_t) _PyNode_SizeOf(node *n);
#define NCH(n) ((n)->n_nchildren)
#define CHILD(n, i) (&(n)->n_child[i])
#define RCHILD(n, i) (CHILD(n, NCH(n) + i))
#define TYPE(n) ((n)->n_type)
#define STR(n) ((n)->n_str)
#define LINENO(n) ((n)->n_lineno)

30
Lib/test/test_decorators.py
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@ -151,21 +151,18 @@ class TestDecorators(unittest.TestCase):
self.assertEqual(counts['double'], 4)
def test_errors(self):
# Test syntax restrictions - these are all compile-time errors:
#
for expr in [ "1+2", "x[3]", "(1, 2)" ]:
# Sanity check: is expr is a valid expression by itself?
compile(expr, "testexpr", "exec")
codestr = "@%s\ndef f(): pass" % expr
self.assertRaises(SyntaxError, compile, codestr, "test", "exec")
# Test SyntaxErrors:
for stmt in ("x,", "x, y", "x = y", "pass", "import sys"):
compile(stmt, "test", "exec") # Sanity check.
with self.assertRaises(SyntaxError):
compile(f"@{stmt}\ndef f(): pass", "test", "exec")
# You can't put multiple decorators on a single line:
#
self.assertRaises(SyntaxError, compile,
"@f1 @f2\ndef f(): pass", "test", "exec")
# Test runtime errors
# Test TypeErrors that used to be SyntaxErrors:
for expr in ("1.+2j", "[1, 2][-1]", "(1, 2)", "True", "...", "None"):
compile(expr, "test", "eval") # Sanity check.
with self.assertRaises(TypeError):
exec(f"@{expr}\ndef f(): pass")
def unimp(func):
raise NotImplementedError
@ -179,6 +176,13 @@ class TestDecorators(unittest.TestCase):
code = compile(codestr, "test", "exec")
self.assertRaises(exc, eval, code, context)
def test_expressions(self):
for expr in (
"(x,)", "(x, y)", "x := y", "(x := y)", "x @y", "(x @ y)", "x[0]",
"w[x].y.z", "w + x - (y + z)", "x(y)()(z)", "[w, x, y][z]", "x.y",
):
compile(f"@{expr}\ndef f(): pass", "test", "exec")
def test_double(self):
class C(object):
@funcattrs(abc=1, xyz="haha")

32
Lib/test/test_grammar.py
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@ -460,7 +460,7 @@ class GrammarTests(unittest.TestCase):
def test_funcdef(self):
### [decorators] 'def' NAME parameters ['->' test] ':' suite
### decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
### decorator: '@' namedexpr_test NEWLINE
### decorators: decorator+
### parameters: '(' [typedargslist] ')'
### typedargslist: ((tfpdef ['=' test] ',')*
@ -666,6 +666,20 @@ class GrammarTests(unittest.TestCase):
def f(x) -> list: pass
self.assertEqual(f.__annotations__, {'return': list})
# Test expressions as decorators (PEP 614):
@False or null
def f(x): pass
@d := null
def f(x): pass
@lambda f: null(f)
def f(x): pass
@[..., null, ...][1]
def f(x): pass
@null(null)(null)
def f(x): pass
@[null][0].__call__.__call__
def f(x): pass
# test closures with a variety of opargs
closure = 1
def f(): return closure
@ -1515,13 +1529,27 @@ class GrammarTests(unittest.TestCase):
def meth2(self, arg): pass
def meth3(self, a1, a2): pass
# decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
# decorator: '@' namedexpr_test NEWLINE
# decorators: decorator+
# decorated: decorators (classdef | funcdef)
def class_decorator(x): return x
@class_decorator
class G: pass
# Test expressions as decorators (PEP 614):
@False or class_decorator
class H: pass
@d := class_decorator
class I: pass
@lambda c: class_decorator(c)
class J: pass
@[..., class_decorator, ...][1]
class K: pass
@class_decorator(class_decorator)(class_decorator)
class L: pass
@[class_decorator][0].__call__.__call__
class M: pass
def test_dictcomps(self):
# dictorsetmaker: ( (test ':' test (comp_for |
# (',' test ':' test)* [','])) |

42
Lib/test/test_parser.py
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@ -226,6 +226,27 @@ class RoundtripLegalSyntaxTestCase(unittest.TestCase):
self.check_suite("@funcattrs()\n"
"def f(): pass")
self.check_suite("@False or x\n"
"def f(): pass")
self.check_suite("@d := x\n"
"def f(): pass")
self.check_suite("@lambda f: x(f)\n"
"def f(): pass")
self.check_suite("@[..., x, ...][1]\n"
"def f(): pass")
self.check_suite("@x(x)(x)\n"
"def f(): pass")
self.check_suite("@(x, x)\n"
"def f(): pass")
self.check_suite("@...\n"
"def f(): pass")
self.check_suite("@None\n"
"def f(): pass")
self.check_suite("@w @(x @y) @(z)\n"
"def f(): pass")
self.check_suite("@w[x].y.z\n"
"def f(): pass")
# keyword-only arguments
self.check_suite("def f(*, a): pass")
self.check_suite("def f(*, a = 5): pass")
@ -270,6 +291,27 @@ class RoundtripLegalSyntaxTestCase(unittest.TestCase):
"@decorator2\n"
"class foo():pass")
self.check_suite("@False or x\n"
"class C: pass")
self.check_suite("@d := x\n"
"class C: pass")
self.check_suite("@lambda f: x(f)\n"
"class C: pass")
self.check_suite("@[..., x, ...][1]\n"
"class C: pass")
self.check_suite("@x(x)(x)\n"
"class C: pass")
self.check_suite("@(x, x)\n"
"class C: pass")
self.check_suite("@...\n"
"class C: pass")
self.check_suite("@None\n"
"class C: pass")
self.check_suite("@w @(x @y) @(z)\n"
"class C: pass")
self.check_suite("@w[x].y.z\n"
"class C: pass")
def test_import_from_statement(self):
self.check_suite("from sys.path import *")
self.check_suite("from sys.path import dirname")

2
Misc/NEWS.d/next/Core and Builtins/2020-02-20-08-12-52.bpo-39702.4_AmyF.rst Normal file
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@ -0,0 +1,2 @@
Relax :term:`decorator` grammar restrictions to allow any valid expression
(:pep:`614`).

72
Python/ast.c
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@ -1691,80 +1691,16 @@ ast_for_arguments(struct compiling *c, const node *n)
return arguments(posonlyargs, posargs, vararg, kwonlyargs, kwdefaults, kwarg, posdefaults, c->c_arena);
}
static expr_ty
ast_for_dotted_name(struct compiling *c, const node *n)
{
expr_ty e;
identifier id;
int lineno, col_offset;
int i;
node *ch;
REQ(n, dotted_name);
lineno = LINENO(n);
col_offset = n->n_col_offset;
ch = CHILD(n, 0);
id = NEW_IDENTIFIER(ch);
if (!id)
return NULL;
e = Name(id, Load, lineno, col_offset,
ch->n_end_lineno, ch->n_end_col_offset, c->c_arena);
if (!e)
return NULL;
for (i = 2; i < NCH(n); i+=2) {
const node *child = CHILD(n, i);
id = NEW_IDENTIFIER(child);
if (!id)
return NULL;
e = Attribute(e, id, Load, lineno, col_offset,
child->n_end_lineno, child->n_end_col_offset, c->c_arena);
if (!e)
return NULL;
}
return e;
}
static expr_ty
ast_for_decorator(struct compiling *c, const node *n)
{
/* decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE */
expr_ty d = NULL;
expr_ty name_expr;
/* decorator: '@' namedexpr_test NEWLINE */
REQ(n, decorator);
REQ(CHILD(n, 0), AT);
REQ(RCHILD(n, -1), NEWLINE);
name_expr = ast_for_dotted_name(c, CHILD(n, 1));
if (!name_expr)
return NULL;
if (NCH(n) == 3) { /* No arguments */
d = name_expr;
name_expr = NULL;
}
else if (NCH(n) == 5) { /* Call with no arguments */
d = Call(name_expr, NULL, NULL,
name_expr->lineno, name_expr->col_offset,
CHILD(n, 3)->n_end_lineno, CHILD(n, 3)->n_end_col_offset,
c->c_arena);
if (!d)
return NULL;
name_expr = NULL;
}
else {
d = ast_for_call(c, CHILD(n, 3), name_expr,
CHILD(n, 1), CHILD(n, 2), CHILD(n, 4));
if (!d)
return NULL;
name_expr = NULL;
}
return d;
REQ(CHILD(n, 2), NEWLINE);
return ast_for_expr(c, CHILD(n, 1));
}
static asdl_seq*

890
Python/graminit.c
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