def visit_If(self, node: ast.If) -> Optional[ast.AST]:
"""Eliminate dead code from if/elif bodies.
If the new `if` statement `body` is empty after eliminating dead code, replace
the body with the `orelse` body and negate the `if` condition.
If both the `body` and `orelse` body are empty, eliminate the node from the
tree."""
new_node = self.generic_visit(node)
assert isinstance(new_node, ast.If)
new_body = _filter_dead_code(new_node.body)
new_orelse = _filter_dead_code(new_node.orelse)
if new_body:
ifstmt = ast.If(
test=new_node.test,
body=new_body,
orelse=new_orelse,
)
elif new_orelse:
ifstmt = ast.If(
test=ast.UnaryOp(op=ast.Not(), operand=new_node.test),
body=new_orelse,
orelse=[],
)
else:
return None
return ast.copy_location(ifstmt, new_node)
def visit_Global(self, node: ast.Global) -> Optional[ast.Global]:
"""Eliminate redundant name declarations inside a Python `global` statement.
Python `global` statements may only refer to a name prior to its declaration.
Global contexts track names in prior `global` declarations and eliminate
redundant names in `global` declarations. If all of the names in the current
`global` statement are redundant, the entire node will be omitted."""
new_names = set(node.names) - self._global_context
self._global_context.update(new_names)
return (ast.copy_location(ast.Global(
names=list(new_names)), node) if new_names else None)
def visit_While(self, node: ast.While) -> Optional[ast.AST]:
"""Eliminate dead code from while bodies."""
new_node = self.generic_visit(node)
assert isinstance(new_node, ast.While)
return ast.copy_location(
ast.While(
test=new_node.test,
body=_filter_dead_code(new_node.body),
orelse=_filter_dead_code(new_node.orelse),
),
new_node,
)
def visit_ExceptHandler(self,
node: ast.ExceptHandler) -> Optional[ast.AST]:
"""Eliminate dead code from except handler bodies."""
new_node = self.generic_visit(node)
assert isinstance(new_node, ast.ExceptHandler)
return ast.copy_location(
ast.ExceptHandler(
type=new_node.type,
name=new_node.name,
body=_filter_dead_code(new_node.body),
),
new_node,
)
def visit_Try(self, node: ast.Try) -> Optional[ast.AST]:
"""Eliminate dead code from except try bodies."""
new_node = self.generic_visit(node)
assert isinstance(new_node, ast.Try)
return ast.copy_location(
ast.Try(
body=_filter_dead_code(new_node.body),
handlers=new_node.handlers,
orelse=_filter_dead_code(new_node.orelse),
finalbody=_filter_dead_code(new_node.finalbody),
),
new_node,
)
def visit_FunctionDef(self, node: ast.FunctionDef) -> Optional[ast.AST]:
"""Eliminate dead code from function bodies."""
with self._new_global_context():
new_node = self.generic_visit(node)
assert isinstance(new_node, ast.FunctionDef)
return ast.copy_location(
ast.FunctionDef(
name=new_node.name,
args=new_node.args,
body=_filter_dead_code(new_node.body),
decorator_list=new_node.decorator_list,
returns=new_node.returns,
),
new_node,
)