bpo-30406: Make async and await proper keywords (#1669)

Per PEP 492, 'async' and 'await' should become proper keywords in 3.7.

4 files changed, 24 insertions, 94 deletions

diff --git a/Lib/lib2to3/Grammar.txt b/Lib/lib2to3/Grammar.txt
index ded032522ba..0bdfcafcf3c 100644
--- a/Lib/lib2to3/Grammar.txt
+++ b/Lib/lib2to3/Grammar.txt
@@ -34,7 +34,7 @@ eval_input: testlist NEWLINE* ENDMARKER
 decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
 decorators: decorator+
 decorated: decorators (classdef | funcdef | async_funcdef)
-async_funcdef: ASYNC funcdef
+async_funcdef: 'async' funcdef
 funcdef: 'def' NAME parameters ['->' test] ':' suite
 parameters: '(' [typedargslist] ')'
 typedargslist: ((tfpdef ['=' test] ',')*
@@ -85,7 +85,7 @@ exec_stmt: 'exec' expr ['in' test [',' test]]
 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)
+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]
 for_stmt: 'for' exprlist 'in' testlist ':' suite ['else' ':' suite]
@@ -124,7 +124,7 @@ shift_expr: arith_expr (('<<'|'>>') arith_expr)*
 arith_expr: term (('+'|'-') term)*
 term: factor (('*'|'@'|'/'|'%'|'//') factor)*
 factor: ('+'|'-'|'~') factor | power
-power: [AWAIT] atom trailer* ['**' factor]
+power: ['await'] atom trailer* ['**' factor]
 atom: ('(' [yield_expr|testlist_gexp] ')' |
        '[' [listmaker] ']' |
        '{' [dictsetmaker] '}' |
@@ -161,7 +161,7 @@ argument: ( test [comp_for] |
 	    star_expr )
 
 comp_iter: comp_for | comp_if
-comp_for: [ASYNC] 'for' exprlist 'in' or_test [comp_iter]
+comp_for: ['async'] 'for' exprlist 'in' or_test [comp_iter]
 comp_if: 'if' old_test [comp_iter]
 
 # As noted above, testlist_safe extends the syntax allowed in list
@@ -180,7 +180,7 @@ comp_if: 'if' old_test [comp_iter]
 #
 # See https://bugs.python.org/issue27494
 old_comp_iter: old_comp_for | old_comp_if
-old_comp_for: [ASYNC] 'for' exprlist 'in' testlist_safe [old_comp_iter]
+old_comp_for: ['async'] 'for' exprlist 'in' testlist_safe [old_comp_iter]
 old_comp_if: 'if' old_test [old_comp_iter]
 
 testlist1: test (',' test)*
diff --git a/Lib/lib2to3/pgen2/token.py b/Lib/lib2to3/pgen2/token.py
index 1a679554d2d..7599396611b 100755
--- a/Lib/lib2to3/pgen2/token.py
+++ b/Lib/lib2to3/pgen2/token.py
@@ -62,10 +62,8 @@ OP = 52
 COMMENT = 53
 NL = 54
 RARROW = 55
-AWAIT = 56
-ASYNC = 57
-ERRORTOKEN = 58
-N_TOKENS = 59
+ERRORTOKEN = 56
+N_TOKENS = 57
 NT_OFFSET = 256
 #--end constants--
 
diff --git a/Lib/lib2to3/pgen2/tokenize.py b/Lib/lib2to3/pgen2/tokenize.py
index 45afc5f4e53..14560e4fddf 100644
--- a/Lib/lib2to3/pgen2/tokenize.py
+++ b/Lib/lib2to3/pgen2/tokenize.py
@@ -234,7 +234,7 @@ class Untokenizer:
         for tok in iterable:
             toknum, tokval = tok[:2]
 
-            if toknum in (NAME, NUMBER, ASYNC, AWAIT):
+            if toknum in (NAME, NUMBER):
                 tokval += ' '
 
             if toknum == INDENT:
@@ -380,12 +380,6 @@ def generate_tokens(readline):
     contline = None
     indents = [0]
 
-    # 'stashed' and 'async_*' are used for async/await parsing
-    stashed = None
-    async_def = False
-    async_def_indent = 0
-    async_def_nl = False
-
     while 1:                                   # loop over lines in stream
         try:
             line = readline()
@@ -426,10 +420,6 @@ def generate_tokens(readline):
                 pos = pos + 1
             if pos == max: break
 
-            if stashed:
-                yield stashed
-                stashed = None
-
             if line[pos] in '#\r\n':           # skip comments or blank lines
                 if line[pos] == '#':
                     comment_token = line[pos:].rstrip('\r\n')
@@ -453,18 +443,8 @@ def generate_tokens(readline):
                         ("<tokenize>", lnum, pos, line))
                 indents = indents[:-1]
 
-                if async_def and async_def_indent >= indents[-1]:
-                    async_def = False
-                    async_def_nl = False
-                    async_def_indent = 0
-
                 yield (DEDENT, '', (lnum, pos), (lnum, pos), line)
 
-            if async_def and async_def_nl and async_def_indent >= indents[-1]:
-                async_def = False
-                async_def_nl = False
-                async_def_indent = 0
-
         else:                                  # continued statement
             if not line:
                 raise TokenError("EOF in multi-line statement", (lnum, 0))
@@ -484,18 +464,10 @@ def generate_tokens(readline):
                     newline = NEWLINE
                     if parenlev > 0:
                         newline = NL
-                    elif async_def:
-                        async_def_nl = True
-                    if stashed:
-                        yield stashed
-                        stashed = None
                     yield (newline, token, spos, epos, line)
 
                 elif initial == '#':
                     assert not token.endswith("\n")
-                    if stashed:
-                        yield stashed
-                        stashed = None
                     yield (COMMENT, token, spos, epos, line)
                 elif token in triple_quoted:
                     endprog = endprogs[token]
@@ -503,9 +475,6 @@ def generate_tokens(readline):
                     if endmatch:                           # all on one line
                         pos = endmatch.end(0)
                         token = line[start:pos]
-                        if stashed:
-                            yield stashed
-                            stashed = None
                         yield (STRING, token, spos, (lnum, pos), line)
                     else:
                         strstart = (lnum, start)           # multiple lines
@@ -523,63 +492,22 @@ def generate_tokens(readline):
                         contline = line
                         break
                     else:                                  # ordinary string
-                        if stashed:
-                            yield stashed
-                            stashed = None
                         yield (STRING, token, spos, epos, line)
                 elif initial in namechars:                 # ordinary name
-                    if token in ('async', 'await'):
-                        if async_def:
-                            yield (ASYNC if token == 'async' else AWAIT,
-                                   token, spos, epos, line)
-                            continue
-
-                    tok = (NAME, token, spos, epos, line)
-                    if token == 'async' and not stashed:
-                        stashed = tok
-                        continue
-
-                    if token == 'def':
-                        if (stashed
-                                and stashed[0] == NAME
-                                and stashed[1] == 'async'):
-
-                            async_def = True
-                            async_def_indent = indents[-1]
-
-                            yield (ASYNC, stashed[1],
-                                   stashed[2], stashed[3],
-                                   stashed[4])
-                            stashed = None
-
-                    if stashed:
-                        yield stashed
-                        stashed = None
-
-                    yield tok
+                    yield (NAME, token, spos, epos, line)
                 elif initial == '\\':                      # continued stmt
                     # This yield is new; needed for better idempotency:
-                    if stashed:
-                        yield stashed
-                        stashed = None
                     yield (NL, token, spos, (lnum, pos), line)
                     continued = 1
                 else:
                     if initial in '([{': parenlev = parenlev + 1
                     elif initial in ')]}': parenlev = parenlev - 1
-                    if stashed:
-                        yield stashed
-                        stashed = None
                     yield (OP, token, spos, epos, line)
             else:
                 yield (ERRORTOKEN, line[pos],
                            (lnum, pos), (lnum, pos+1), line)
                 pos = pos + 1
 
-    if stashed:
-        yield stashed
-        stashed = None
-
     for indent in indents[1:]:                 # pop remaining indent levels
         yield (DEDENT, '', (lnum, 0), (lnum, 0), '')
     yield (ENDMARKER, '', (lnum, 0), (lnum, 0), '')
diff --git a/Lib/lib2to3/tests/test_parser.py b/Lib/lib2to3/tests/test_parser.py
index 2efcb80c2f9..dc94a69036a 100644
--- a/Lib/lib2to3/tests/test_parser.py
+++ b/Lib/lib2to3/tests/test_parser.py
@@ -167,34 +167,34 @@ class TestAsyncAwait(GrammarTest):
             async def foo(): await x
         """)
 
-        self.invalid_syntax("await x")
-        self.invalid_syntax("""def foo():
-                                   await x""")
+        self.validate("await x")
+        self.validate("""def foo():
+                        await x""")
 
-        self.invalid_syntax("""def foo():
+        self.validate("""def foo():
             def foo(): pass
             async def foo(): pass
             await x
         """)
 
     def test_async_var(self):
-        self.validate("""async = 1""")
-        self.validate("""await = 1""")
-        self.validate("""def async(): pass""")
+        self.invalid_syntax("""async = 1""")
+        self.invalid_syntax("""await = 1""")
+        self.invalid_syntax("""def async(): pass""")
 
     def test_async_with(self):
         self.validate("""async def foo():
                              async for a in b: pass""")
 
-        self.invalid_syntax("""def foo():
-                                   async for a in b: pass""")
+        self.validate("""def foo():
+                             async for a in b: pass""")
 
     def test_async_for(self):
         self.validate("""async def foo():
                              async with a: pass""")
 
-        self.invalid_syntax("""def foo():
-                                   async with a: pass""")
+        self.validate("""def foo():
+                             async with a: pass""")
 
 
 class TestRaiseChanges(GrammarTest):
@@ -477,3 +477,7 @@ def diff(fn, result):
             os.remove("@")
         except OSError:
             pass
+
+
+if __name__ == '__main__':
+    unittest.main()