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|
import ast
import copy
import dis
import sys
sentinel_rep = 2
# generate sentinel at runtime to keep it out of the bytecode
# this allows the algorithm to check also this file
sentinel = "xsglegahghegflgfaih" * sentinel_rep
def constant(value):
if sys.version_info >= (3, 6):
return ast.Constant(value=value)
elif isinstance(value, int):
return ast.Num(value)
elif isinstance(value, str):
return ast.Str(value)
else:
raise TypeError
def index(value):
if sys.version_info >= (3, 9):
return constant(value)
else:
return ast.Index(constant(value))
class DeadcodeTransformer(ast.NodeTransformer):
def visit(self, node):
constant_type = (
ast.Constant
if sys.version_info >= (3, 6)
else (ast.Num, ast.Str, ast.Bytes, ast.NameConstant, ast.Ellipsis)
)
if getattr(node, "_check_is_deadcode", False):
if isinstance(node, constant_type) and isinstance(node.value, str):
# docstring for example
return constant(sentinel)
elif isinstance(node, ast.stmt):
return ast.Expr(
value=ast.Call(
func=ast.Name(id="foo", ctx=ast.Load()),
args=[constant(sentinel)],
keywords=[],
)
)
elif isinstance(node, ast.expr):
if hasattr(node, "ctx") and isinstance(node.ctx, (ast.Store, ast.Del)):
return ast.Subscript(
value=ast.Name(id="foo", ctx=ast.Load()),
slice=index(sentinel),
ctx=node.ctx,
)
else:
return ast.Subscript(
value=ast.Tuple(
elts=[node, constant(sentinel)],
ctx=ast.Load(),
),
slice=index(0),
ctx=ast.Load(),
)
else:
raise TypeError(node)
else:
return super().visit(node)
def is_deadcode(node):
if isinstance(node, ast.withitem):
node = node.context_expr
if isinstance(node, ast.ExceptHandler):
node = node.body[0]
if sys.version_info >= (3,8) and isinstance(node.parent, ast.NamedExpr) and node.parent.target is node:
node = node.parent
if sys.version_info >= (3,12) and isinstance(node.parent,ast.TypeAlias):
node = node.parent
if (
sys.version_info >= (3, 6)
and isinstance(node.parent, ast.AnnAssign)
and node.parent.target is node
):
# AnnAssign.target has to be ast.Name
node = node.parent
if hasattr(node, "_is_deadcode"):
return node._is_deadcode
node._check_is_deadcode = True
module = node
while hasattr(module, "parent"):
module = module.parent
assert isinstance(module, ast.Module)
# create working copy of the ast
module2 = copy.deepcopy(module)
del node._check_is_deadcode
module2 = ast.fix_missing_locations(DeadcodeTransformer().visit(module2))
try:
code = compile(module2, "<filename>", "exec")
except:
print(ast.dump(module2))
raise
visited = set()
def contains_sentinel(code):
if code in visited:
return False
for inst in dis.get_instructions(code):
arg = inst.argval
if isinstance(arg, type(code)) and contains_sentinel(arg):
return True
if arg == sentinel:
return True
visited.add(code)
return False
node._is_deadcode = not contains_sentinel(code)
return node._is_deadcode
|
