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bpo-43892: Make match patterns explicit in the AST (GH-25585)
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Co-authored-by: Brandt Bucher <brandtbucher@gmail.com>
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@ncoghlan @brandtbucher
ncoghlan and brandtbucher committed Apr 29, 2021
1 parent e52ab42 commit 1e7b858
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Showing 20 changed files with 3,598 additions and 1,515 deletions.
318 changes: 282 additions & 36 deletions Doc/library/ast.rst
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155 changes: 101 additions & 54 deletions Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -234,20 +234,20 @@ case_block[match_case_ty]:
_PyAST_match_case(pattern, guard, body, p->arena) }
guard[expr_ty]: 'if' guard=named_expression { guard }

patterns[expr_ty]:
| values[asdl_expr_seq*]=open_sequence_pattern {
_PyAST_Tuple(values, Load, EXTRA) }
patterns[pattern_ty]:
| patterns[asdl_pattern_seq*]=open_sequence_pattern {
_PyAST_MatchSequence(patterns, EXTRA) }
| pattern
pattern[expr_ty]:
pattern[pattern_ty]:
| as_pattern
| or_pattern
as_pattern[expr_ty]:
| pattern=or_pattern 'as' target=capture_pattern {
as_pattern[pattern_ty]:
| pattern=or_pattern 'as' target=pattern_capture_target {
_PyAST_MatchAs(pattern, target->v.Name.id, EXTRA) }
or_pattern[expr_ty]:
| patterns[asdl_expr_seq*]='|'.closed_pattern+ {
or_pattern[pattern_ty]:
| patterns[asdl_pattern_seq*]='|'.closed_pattern+ {
asdl_seq_LEN(patterns) == 1 ? asdl_seq_GET(patterns, 0) : _PyAST_MatchOr(patterns, EXTRA) }
closed_pattern[expr_ty]:
closed_pattern[pattern_ty]:
| literal_pattern
| capture_pattern
| wildcard_pattern
Expand All @@ -257,78 +257,125 @@ closed_pattern[expr_ty]:
| mapping_pattern
| class_pattern

literal_pattern[expr_ty]:
# Literal patterns are used for equality and identity constraints
literal_pattern[pattern_ty]:
| value=signed_number !('+' | '-') { _PyAST_MatchValue(value, EXTRA) }
| value=complex_number { _PyAST_MatchValue(value, EXTRA) }
| value=strings { _PyAST_MatchValue(value, EXTRA) }
| 'None' { _PyAST_MatchSingleton(Py_None, EXTRA) }
| 'True' { _PyAST_MatchSingleton(Py_True, EXTRA) }
| 'False' { _PyAST_MatchSingleton(Py_False, EXTRA) }

# Literal expressions are used to restrict permitted mapping pattern keys
literal_expr[expr_ty]:
| signed_number !('+' | '-')
| real=signed_number '+' imag=NUMBER { _PyAST_BinOp(real, Add, imag, EXTRA) }
| real=signed_number '-' imag=NUMBER { _PyAST_BinOp(real, Sub, imag, EXTRA) }
| complex_number
| strings
| 'None' { _PyAST_Constant(Py_None, NULL, EXTRA) }
| 'True' { _PyAST_Constant(Py_True, NULL, EXTRA) }
| 'False' { _PyAST_Constant(Py_False, NULL, EXTRA) }

complex_number[expr_ty]:
| real=signed_number '+' imag=imaginary_number { _PyAST_BinOp(real, Add, imag, EXTRA) }
| real=signed_number '-' imag=imaginary_number { _PyAST_BinOp(real, Sub, imag, EXTRA) }

signed_number[expr_ty]:
| NUMBER
| '-' number=NUMBER { _PyAST_UnaryOp(USub, number, EXTRA) }

capture_pattern[expr_ty]:
imaginary_number[expr_ty]:
| imag=NUMBER { _PyPegen_ensure_imaginary(p, imag) }

capture_pattern[pattern_ty]:
| target=pattern_capture_target { _PyAST_MatchAs(NULL, target->v.Name.id, EXTRA) }

pattern_capture_target[expr_ty]:
| !"_" name=NAME !('.' | '(' | '=') {
_PyPegen_set_expr_context(p, name, Store) }

wildcard_pattern[expr_ty]:
| "_" { _PyAST_Name(CHECK(PyObject*, _PyPegen_new_identifier(p, "_")), Store, EXTRA) }
wildcard_pattern[pattern_ty]:
| "_" { _PyAST_MatchAs(NULL, NULL, EXTRA) }

value_pattern[expr_ty]:
| attr=attr !('.' | '(' | '=') { attr }
value_pattern[pattern_ty]:
| attr=attr !('.' | '(' | '=') { _PyAST_MatchValue(attr, EXTRA) }
attr[expr_ty]:
| value=name_or_attr '.' attr=NAME {
_PyAST_Attribute(value, attr->v.Name.id, Load, EXTRA) }
name_or_attr[expr_ty]:
| attr
| NAME

group_pattern[expr_ty]:
group_pattern[pattern_ty]:
| '(' pattern=pattern ')' { pattern }

sequence_pattern[expr_ty]:
| '[' values=maybe_sequence_pattern? ']' { _PyAST_List(values, Load, EXTRA) }
| '(' values=open_sequence_pattern? ')' { _PyAST_Tuple(values, Load, EXTRA) }
sequence_pattern[pattern_ty]:
| '[' patterns=maybe_sequence_pattern? ']' { _PyAST_MatchSequence(patterns, EXTRA) }
| '(' patterns=open_sequence_pattern? ')' { _PyAST_MatchSequence(patterns, EXTRA) }
open_sequence_pattern[asdl_seq*]:
| value=maybe_star_pattern ',' values=maybe_sequence_pattern? {
_PyPegen_seq_insert_in_front(p, value, values) }
| pattern=maybe_star_pattern ',' patterns=maybe_sequence_pattern? {
_PyPegen_seq_insert_in_front(p, pattern, patterns) }
maybe_sequence_pattern[asdl_seq*]:
| values=','.maybe_star_pattern+ ','? { values }
maybe_star_pattern[expr_ty]:
| patterns=','.maybe_star_pattern+ ','? { patterns }
maybe_star_pattern[pattern_ty]:
| star_pattern
| pattern
star_pattern[expr_ty]:
| '*' value=(capture_pattern | wildcard_pattern) {
_PyAST_Starred(value, Store, EXTRA) }

mapping_pattern[expr_ty]:
| '{' items=items_pattern? '}' {
_PyAST_Dict(CHECK(asdl_expr_seq*, _PyPegen_get_keys(p, items)), CHECK(asdl_expr_seq*, _PyPegen_get_values(p, items)), EXTRA) }
star_pattern[pattern_ty]:
| '*' target=pattern_capture_target {
_PyAST_MatchStar(target->v.Name.id, EXTRA) }
| '*' wildcard_pattern {
_PyAST_MatchStar(NULL, EXTRA) }

mapping_pattern[pattern_ty]:
| '{' '}' {
_PyAST_MatchMapping(NULL, NULL, NULL, EXTRA) }
| '{' rest=double_star_pattern ','? '}' {
_PyAST_MatchMapping(NULL, NULL, rest->v.Name.id, EXTRA) }
| '{' items=items_pattern ',' rest=double_star_pattern ','? '}' {
_PyAST_MatchMapping(
CHECK(asdl_expr_seq*, _PyPegen_get_pattern_keys(p, items)),
CHECK(asdl_pattern_seq*, _PyPegen_get_patterns(p, items)),
rest->v.Name.id,
EXTRA) }
| '{' items=items_pattern ','? '}' {
_PyAST_MatchMapping(
CHECK(asdl_expr_seq*, _PyPegen_get_pattern_keys(p, items)),
CHECK(asdl_pattern_seq*, _PyPegen_get_patterns(p, items)),
NULL,
EXTRA) }
items_pattern[asdl_seq*]:
| items=','.key_value_pattern+ ','? { items }
key_value_pattern[KeyValuePair*]:
| key=(literal_pattern | value_pattern) ':' value=pattern {
_PyPegen_key_value_pair(p, key, value) }
| double_star_pattern
double_star_pattern[KeyValuePair*]:
| '**' value=capture_pattern { _PyPegen_key_value_pair(p, NULL, value) }

class_pattern[expr_ty]:
| func=name_or_attr '(' ')' { _PyAST_Call(func, NULL, NULL, EXTRA) }
| func=name_or_attr '(' args=positional_patterns ','? ')' {
_PyAST_Call(func, args, NULL, EXTRA) }
| func=name_or_attr '(' keywords=keyword_patterns ','? ')' {
_PyAST_Call(func, NULL, keywords, EXTRA) }
| func=name_or_attr '(' args=positional_patterns ',' keywords=keyword_patterns ','? ')' {
_PyAST_Call(func, args, keywords, EXTRA) }
positional_patterns[asdl_expr_seq*]:
| args[asdl_expr_seq*]=','.pattern+ { args }
keyword_patterns[asdl_keyword_seq*]:
| keywords[asdl_keyword_seq*]=','.keyword_pattern+ { keywords }
keyword_pattern[keyword_ty]:
| arg=NAME '=' value=pattern { _PyAST_keyword(arg->v.Name.id, value, EXTRA) }
| items=','.key_value_pattern+ { items }
key_value_pattern[KeyPatternPair*]:
| key=(literal_expr | attr) ':' pattern=pattern {
_PyPegen_key_pattern_pair(p, key, pattern) }
double_star_pattern[expr_ty]:
| '**' target=pattern_capture_target { target }

class_pattern[pattern_ty]:
| cls=name_or_attr '(' ')' {
_PyAST_MatchClass(cls, NULL, NULL, NULL, EXTRA) }
| cls=name_or_attr '(' patterns=positional_patterns ','? ')' {
_PyAST_MatchClass(cls, patterns, NULL, NULL, EXTRA) }
| cls=name_or_attr '(' keywords=keyword_patterns ','? ')' {
_PyAST_MatchClass(
cls, NULL,
CHECK(asdl_identifier_seq*, _PyPegen_map_names_to_ids(p,
CHECK(asdl_expr_seq*, _PyPegen_get_pattern_keys(p, keywords)))),
CHECK(asdl_pattern_seq*, _PyPegen_get_patterns(p, keywords)),
EXTRA) }
| cls=name_or_attr '(' patterns=positional_patterns ',' keywords=keyword_patterns ','? ')' {
_PyAST_MatchClass(
cls,
patterns,
CHECK(asdl_identifier_seq*, _PyPegen_map_names_to_ids(p,
CHECK(asdl_expr_seq*, _PyPegen_get_pattern_keys(p, keywords)))),
CHECK(asdl_pattern_seq*, _PyPegen_get_patterns(p, keywords)),
EXTRA) }
positional_patterns[asdl_pattern_seq*]:
| args[asdl_pattern_seq*]=','.pattern+ { args }
keyword_patterns[asdl_seq*]:
| keywords[asdl_seq*]=','.keyword_pattern+ { keywords }
keyword_pattern[KeyPatternPair*]:
| arg=NAME '=' value=pattern { _PyPegen_key_pattern_pair(p, arg, value) }

return_stmt[stmt_ty]:
| 'return' a=[star_expressions] { _PyAST_Return(a, EXTRA) }
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108 changes: 89 additions & 19 deletions Include/internal/pycore_ast.h
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