Drop support for parsing Python 2 (#3933)

CHANGES.md

@@ -40,6 +40,9 @@
 
 <!-- Changes to Black's terminal output and error messages -->
 
+- Black no longer attempts to provide special errors for attempting to format Python 2
+  code (#3933)
+
 ### _Blackd_
 
 <!-- Changes to blackd -->

src/black/parsing.py

@@ -3,7 +3,7 @@
 """
 import ast
 import sys
-from typing import Final, Iterable, Iterator, List, Set, Tuple
+from typing import Iterable, Iterator, List, Set, Tuple
 
 from black.mode import VERSION_TO_FEATURES, Feature, TargetVersion, supports_feature
 from black.nodes import syms
@@ -14,8 +14,6 @@
 from blib2to3.pgen2.tokenize import TokenError
 from blib2to3.pytree import Leaf, Node
 
-PY2_HINT: Final = "Python 2 support was removed in version 22.0."
-
 
 class InvalidInput(ValueError):
     """Raised when input source code fails all parse attempts."""
@@ -26,9 +24,9 @@ def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
         # No target_version specified, so try all grammars.
         return [
             # Python 3.7-3.9
-            pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords,
+            pygram.python_grammar_async_keywords,
             # Python 3.0-3.6
-            pygram.python_grammar_no_print_statement_no_exec_statement,
+            pygram.python_grammar,
             # Python 3.10+
             pygram.python_grammar_soft_keywords,
         ]
@@ -39,12 +37,10 @@ def get_grammars(target_versions: Set[TargetVersion]) -> List[Grammar]:
         target_versions, Feature.ASYNC_IDENTIFIERS
     ) and not supports_feature(target_versions, Feature.PATTERN_MATCHING):
         # Python 3.7-3.9
-        grammars.append(
-            pygram.python_grammar_no_print_statement_no_exec_statement_async_keywords
-        )
+        grammars.append(pygram.python_grammar_async_keywords)
     if not supports_feature(target_versions, Feature.ASYNC_KEYWORDS):
         # Python 3.0-3.6
-        grammars.append(pygram.python_grammar_no_print_statement_no_exec_statement)
+        grammars.append(pygram.python_grammar)
     if any(Feature.PATTERN_MATCHING in VERSION_TO_FEATURES[v] for v in target_versions):
         # Python 3.10+
         grammars.append(pygram.python_grammar_soft_keywords)
@@ -89,14 +85,6 @@ def lib2to3_parse(src_txt: str, target_versions: Iterable[TargetVersion] = ()) -
         # Choose the latest version when raising the actual parsing error.
         assert len(errors) >= 1
         exc = errors[max(errors)]
-
-        if matches_grammar(src_txt, pygram.python_grammar) or matches_grammar(
-            src_txt, pygram.python_grammar_no_print_statement
-        ):
-            original_msg = exc.args[0]
-            msg = f"{original_msg}\n{PY2_HINT}"
-            raise InvalidInput(msg) from None
-
         raise exc from None
 
     if isinstance(result, Leaf):

src/blib2to3/Grammar.txt

@@ -80,17 +80,15 @@ vfplist: vfpdef (',' vfpdef)* [',']
 
 stmt: simple_stmt | compound_stmt
 simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE
-small_stmt: (type_stmt | expr_stmt | print_stmt  | del_stmt | pass_stmt | flow_stmt |
-             import_stmt | global_stmt | exec_stmt | assert_stmt)
+small_stmt: (type_stmt | expr_stmt | del_stmt | pass_stmt | flow_stmt |
+             import_stmt | global_stmt | assert_stmt)
 expr_stmt: testlist_star_expr (annassign | augassign (yield_expr|testlist) |
                      ('=' (yield_expr|testlist_star_expr))*)
 annassign: ':' test ['=' (yield_expr|testlist_star_expr)]
 testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [',']
 augassign: ('+=' | '-=' | '*=' | '@=' | '/=' | '%=' | '&=' | '|=' | '^=' |
             '<<=' | '>>=' | '**=' | '//=')
 # For normal and annotated assignments, additional restrictions enforced by the interpreter
-print_stmt: 'print' ( [ test (',' test)* [','] ] |
-                      '>>' test [ (',' test)+ [','] ] )
 del_stmt: 'del' exprlist
 pass_stmt: 'pass'
 flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt | yield_stmt
@@ -109,7 +107,6 @@ import_as_names: import_as_name (',' import_as_name)* [',']
 dotted_as_names: dotted_as_name (',' dotted_as_name)*
 dotted_name: NAME ('.' NAME)*
 global_stmt: ('global' | 'nonlocal') NAME (',' NAME)*
-exec_stmt: 'exec' expr ['in' test [',' test]]
 assert_stmt: 'assert' test [',' test]
 type_stmt: "type" NAME [typeparams] '=' expr
 

src/blib2to3/pygram.py

@@ -63,7 +63,6 @@ class _python_symbols(Symbols):
     encoding_decl: int
     eval_input: int
     except_clause: int
-    exec_stmt: int
     expr: int
     expr_stmt: int
     exprlist: int
@@ -97,7 +96,6 @@ class _python_symbols(Symbols):
     pattern: int
     patterns: int
     power: int
-    print_stmt: int
     raise_stmt: int
     return_stmt: int
     shift_expr: int
@@ -153,22 +151,16 @@ class _pattern_symbols(Symbols):
 
 
 python_grammar: Grammar
-python_grammar_no_print_statement: Grammar
-python_grammar_no_print_statement_no_exec_statement: Grammar
-python_grammar_no_print_statement_no_exec_statement_async_keywords: Grammar
-python_grammar_no_exec_statement: Grammar
-pattern_grammar: Grammar
+python_grammar_async_keywords: Grammar
 python_grammar_soft_keywords: Grammar
-
+pattern_grammar: Grammar
 python_symbols: _python_symbols
 pattern_symbols: _pattern_symbols
 
 
 def initialize(cache_dir: Union[str, "os.PathLike[str]", None] = None) -> None:
     global python_grammar
-    global python_grammar_no_print_statement
-    global python_grammar_no_print_statement_no_exec_statement
-    global python_grammar_no_print_statement_no_exec_statement_async_keywords
+    global python_grammar_async_keywords
     global python_grammar_soft_keywords
     global python_symbols
     global pattern_grammar
@@ -180,38 +172,25 @@ def initialize(cache_dir: Union[str, "os.PathLike[str]", None] = None) -> None:
         os.path.dirname(__file__), "PatternGrammar.txt"
     )
 
-    # Python 2
     python_grammar = driver.load_packaged_grammar("blib2to3", _GRAMMAR_FILE, cache_dir)
-    python_grammar.version = (2, 0)
+    assert "print" not in python_grammar.keywords
+    assert "exec" not in python_grammar.keywords
 
     soft_keywords = python_grammar.soft_keywords.copy()
     python_grammar.soft_keywords.clear()
 
     python_symbols = _python_symbols(python_grammar)
 
-    # Python 2 + from __future__ import print_function
-    python_grammar_no_print_statement = python_grammar.copy()
-    del python_grammar_no_print_statement.keywords["print"]
-
     # Python 3.0-3.6
-    python_grammar_no_print_statement_no_exec_statement = python_grammar.copy()
-    del python_grammar_no_print_statement_no_exec_statement.keywords["print"]
-    del python_grammar_no_print_statement_no_exec_statement.keywords["exec"]
-    python_grammar_no_print_statement_no_exec_statement.version = (3, 0)
+    python_grammar.version = (3, 0)
 
     # Python 3.7+
-    python_grammar_no_print_statement_no_exec_statement_async_keywords = (
-        python_grammar_no_print_statement_no_exec_statement.copy()
-    )
-    python_grammar_no_print_statement_no_exec_statement_async_keywords.async_keywords = (
-        True
-    )
-    python_grammar_no_print_statement_no_exec_statement_async_keywords.version = (3, 7)
+    python_grammar_async_keywords = python_grammar.copy()
+    python_grammar_async_keywords.async_keywords = True
+    python_grammar_async_keywords.version = (3, 7)
 
     # Python 3.10+
-    python_grammar_soft_keywords = (
-        python_grammar_no_print_statement_no_exec_statement_async_keywords.copy()
-    )
+    python_grammar_soft_keywords = python_grammar_async_keywords.copy()
     python_grammar_soft_keywords.soft_keywords = soft_keywords
     python_grammar_soft_keywords.version = (3, 10)
 

tests/test_format.py

@@ -155,12 +155,6 @@ def test_fast_cases(filename: str) -> None:
     assert_format(source, expected, fast=True)
 
 
-def test_python_2_hint() -> None:
-    with pytest.raises(black.parsing.InvalidInput) as exc_info:
-        assert_format("print 'daylily'", "print 'daylily'")
-    exc_info.match(black.parsing.PY2_HINT)
-
-
 @pytest.mark.filterwarnings("ignore:invalid escape sequence.*:DeprecationWarning")
 def test_docstring_no_string_normalization() -> None:
     """Like test_docstring but with string normalization off."""