From 96c5f5a3a3fabf43e8114d0dbc30bed409da1ba6 Mon Sep 17 00:00:00 2001 From: Tim Hatch Date: Fri, 3 Apr 2020 12:14:15 -0700 Subject: [PATCH] [3.7] bpo-36541: lib2to3: Support named assignment expressions (GH-12702) (GH-19317) lib2to3: Support named assignment expressions (GH-12702) There are two copies of the grammar -- the one used by Python itself as Grammar/Grammar, and the one used by lib2to3 which has necessarily diverged at Lib/lib2to3/Grammar.txt because it needs to support older syntax an we want it to be reasonable stable to avoid requiring fixer rewrites. This brings suport for syntax like `if x:= foo():` to match what the live Python grammar does. This should've been added at the time of the walrus operator itself, but lib2to3 being independent is often overlooked. So we do consider this a bugfix rather than enhancement. (cherry picked from commit 3c3aa4516c70753de06bb142b6793d01330fcf0f) Co-authored-by: Tim Hatch --- Lib/lib2to3/Grammar.txt | 10 ++++++---- Lib/lib2to3/pgen2/grammar.py | 1 + Lib/lib2to3/pgen2/token.py | 3 ++- Lib/lib2to3/pgen2/tokenize.py | 2 +- Lib/lib2to3/tests/test_parser.py | 15 +++++++++++++++ .../2019-06-18-19-38-27.bpo-36541.XI8mi1.rst | 2 ++ 6 files changed, 27 insertions(+), 6 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2019-06-18-19-38-27.bpo-36541.XI8mi1.rst diff --git a/Lib/lib2to3/Grammar.txt b/Lib/lib2to3/Grammar.txt index 68b73868b582..8ce7fd8a89da 100644 --- a/Lib/lib2to3/Grammar.txt +++ b/Lib/lib2to3/Grammar.txt @@ -67,8 +67,8 @@ assert_stmt: 'assert' test [',' test] compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated | async_stmt async_stmt: ASYNC (funcdef | with_stmt | for_stmt) -if_stmt: 'if' test ':' suite ('elif' test ':' suite)* ['else' ':' suite] -while_stmt: 'while' test ':' suite ['else' ':' suite] +if_stmt: 'if' namedexpr_test ':' suite ('elif' namedexpr_test ':' suite)* ['else' ':' suite] +while_stmt: 'while' namedexpr_test ':' suite ['else' ':' suite] for_stmt: 'for' exprlist 'in' testlist ':' suite ['else' ':' suite] try_stmt: ('try' ':' suite ((except_clause ':' suite)+ @@ -91,6 +91,7 @@ testlist_safe: old_test [(',' old_test)+ [',']] old_test: or_test | old_lambdef old_lambdef: 'lambda' [varargslist] ':' old_test +namedexpr_test: test [':=' test] test: or_test ['if' or_test 'else' test] | lambdef or_test: and_test ('or' and_test)* and_test: not_test ('and' not_test)* @@ -111,8 +112,8 @@ atom: ('(' [yield_expr|testlist_gexp] ')' | '{' [dictsetmaker] '}' | '`' testlist1 '`' | NAME | NUMBER | STRING+ | '.' '.' '.') -listmaker: (test|star_expr) ( comp_for | (',' (test|star_expr))* [','] ) -testlist_gexp: (test|star_expr) ( comp_for | (',' (test|star_expr))* [','] ) +listmaker: (namedexpr_test|star_expr) ( comp_for | (',' (namedexpr_test|star_expr))* [','] ) +testlist_gexp: (namedexpr_test|star_expr) ( comp_for | (',' (namedexpr_test|star_expr))* [','] ) lambdef: 'lambda' [varargslist] ':' test trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME subscriptlist: subscript (',' subscript)* [','] @@ -137,6 +138,7 @@ arglist: argument (',' argument)* [','] # multiple (test comp_for) arguments are blocked; keyword unpackings # that precede iterable unpackings are blocked; etc. argument: ( test [comp_for] | + test ':=' test | test '=' test | '**' test | '*' test ) diff --git a/Lib/lib2to3/pgen2/grammar.py b/Lib/lib2to3/pgen2/grammar.py index 088c58bfa99c..997fdf530f72 100644 --- a/Lib/lib2to3/pgen2/grammar.py +++ b/Lib/lib2to3/pgen2/grammar.py @@ -202,6 +202,7 @@ opmap_raw = """ // DOUBLESLASH //= DOUBLESLASHEQUAL -> RARROW +:= COLONEQUAL """ opmap = {} diff --git a/Lib/lib2to3/pgen2/token.py b/Lib/lib2to3/pgen2/token.py index 1a679554d2db..5f6612f5b306 100755 --- a/Lib/lib2to3/pgen2/token.py +++ b/Lib/lib2to3/pgen2/token.py @@ -65,7 +65,8 @@ RARROW = 55 AWAIT = 56 ASYNC = 57 ERRORTOKEN = 58 -N_TOKENS = 59 +COLONEQUAL = 59 +N_TOKENS = 60 NT_OFFSET = 256 #--end constants-- diff --git a/Lib/lib2to3/pgen2/tokenize.py b/Lib/lib2to3/pgen2/tokenize.py index 279d322971da..94dd792805ea 100644 --- a/Lib/lib2to3/pgen2/tokenize.py +++ b/Lib/lib2to3/pgen2/tokenize.py @@ -93,7 +93,7 @@ Operator = group(r"\*\*=?", r">>=?", r"<<=?", r"<>", r"!=", r"~") Bracket = '[][(){}]' -Special = group(r'\r?\n', r'[:;.,`@]') +Special = group(r'\r?\n', r':=', r'[:;.,`@]') Funny = group(Operator, Bracket, Special) PlainToken = group(Number, Funny, String, Name) diff --git a/Lib/lib2to3/tests/test_parser.py b/Lib/lib2to3/tests/test_parser.py index 7ec881e01a9f..753c846b7be7 100644 --- a/Lib/lib2to3/tests/test_parser.py +++ b/Lib/lib2to3/tests/test_parser.py @@ -629,6 +629,21 @@ class TestLiterals(GrammarTest): self.validate(s) +class TestNamedAssignments(GrammarTest): + + def test_named_assignment_if(self): + driver.parse_string("if f := x(): pass\n") + + def test_named_assignment_while(self): + driver.parse_string("while f := x(): pass\n") + + def test_named_assignment_generator(self): + driver.parse_string("any((lastNum := num) == 1 for num in [1, 2, 3])\n") + + def test_named_assignment_listcomp(self): + driver.parse_string("[(lastNum := num) == 1 for num in [1, 2, 3]]\n") + + def diff_texts(a, b, filename): a = a.splitlines() b = b.splitlines() diff --git a/Misc/NEWS.d/next/Library/2019-06-18-19-38-27.bpo-36541.XI8mi1.rst b/Misc/NEWS.d/next/Library/2019-06-18-19-38-27.bpo-36541.XI8mi1.rst new file mode 100644 index 000000000000..e7b9dd648b40 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2019-06-18-19-38-27.bpo-36541.XI8mi1.rst @@ -0,0 +1,2 @@ +lib2to3 now recognizes named assignment expressions (the walrus operator, +``:=``) -- 2.47.3