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visitors.py
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visitors.py
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"""Various visitors/error classes that are too small to warrant getting their own file."""
from __future__ import annotations
import ast
from typing import TYPE_CHECKING, Any, cast
import libcst as cst
from .flake8asyncvisitor import Flake8AsyncVisitor, Flake8AsyncVisitor_cst
from .helpers import (
disabled_by_default,
error_class,
error_class_cst,
get_matching_call,
has_decorator,
identifier_to_string,
)
if TYPE_CHECKING:
from collections.abc import Mapping
LIBRARIES = ("trio", "anyio", "asyncio")
@error_class
class Visitor106(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC106": "{0} must be imported with `import {0}` for the linter to work.",
}
def visit_ImportFrom(self, node: ast.ImportFrom):
if node.module in LIBRARIES:
self.error(node, node.module)
def visit_Import(self, node: ast.Import):
for name in node.names:
if name.name in LIBRARIES and name.asname is not None:
self.error(node, name.name)
@error_class
class Visitor109(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC109": (
"Async function definition with a `timeout` parameter - use "
"`{}.[fail/move_on]_[after/at]` instead."
),
}
def visit_AsyncFunctionDef(self, node: ast.AsyncFunctionDef):
# pending configuration or a more sophisticated check, ignore
# all functions with a decorator
if node.decorator_list:
return
args = node.args
for arg in (*args.posonlyargs, *args.args, *args.kwonlyargs):
if arg.arg == "timeout":
self.error(arg, self.library_str)
@error_class
class Visitor110(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC110": (
"`while <condition>: await {0}.sleep()` should be replaced by "
"a `{0}.Event`."
),
}
def visit_While(self, node: ast.While):
if (
len(node.body) == 1
and isinstance(node.body[0], ast.Expr)
and isinstance(node.body[0].value, ast.Await)
and (
get_matching_call(node.body[0].value.value, "sleep", "sleep_until")
or (
# get_matching_call doesn't (currently) support checking for trio.x.y
isinstance(call := node.body[0].value.value, ast.Call)
and isinstance(call.func, ast.Attribute)
and call.func.attr == "checkpoint"
and isinstance(call.func.value, ast.Attribute)
and call.func.value.attr == "lowlevel"
and isinstance(call.func.value.value, ast.Name)
and call.func.value.value.id in ("trio", "anyio")
)
)
):
self.error(node, self.library_str)
@error_class
class Visitor112(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC112": (
"Redundant {1} {0}, consider replacing with directly awaiting "
"the function call."
),
}
# if with has a withitem `trio.open_nursery() as <X>`,
# and the body is only a single expression <X>.start[_soon](),
# and does not pass <X> as a parameter to the expression
def visit_With(self, node: ast.With | ast.AsyncWith):
# body is single expression
if len(node.body) != 1 or not isinstance(node.body[0], ast.Expr):
return
for item in node.items:
# get variable name <X>
if not isinstance(item.optional_vars, ast.Name):
continue
var_name = item.optional_vars.id
start_methods: tuple[str, ...] = ("start", "start_soon")
# check for trio.open_nursery and anyio.create_task_group
if get_matching_call(item.context_expr, "open_nursery", base="trio"):
nursery_type = "nursery"
elif get_matching_call(
item.context_expr, "create_task_group", base="anyio"
):
nursery_type = "taskgroup"
# check for asyncio.TaskGroup
elif get_matching_call(item.context_expr, "TaskGroup", base="asyncio"):
nursery_type = "taskgroup"
start_methods = ("create_task",)
else:
# incorrectly marked as not covered on py39
continue # pragma: no cover # https://github.com/nedbat/coveragepy/issues/198
body_call = node.body[0].value
if isinstance(body_call, ast.Await):
body_call = body_call.value
# `isinstance(..., ast.Call)` is done in get_matching_call
body_call = cast("ast.Call", body_call)
if (
get_matching_call(body_call, *start_methods, base=var_name)
# check for presence of <X> as parameter
and not any(
(isinstance(n, ast.Name) and n.id == var_name)
for n in self.walk(*body_call.args, *body_call.keywords)
)
):
self.error(item.context_expr, var_name, nursery_type)
visit_AsyncWith = visit_With
# used in 113 and 114
STARTABLE_CALLS = (
"run_process",
"serve_ssl_over_tcp",
"serve_tcp",
"serve_listeners",
"serve",
)
@error_class
class Visitor113(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC113": (
"Dangerous `.start_soon()`, function might not be executed before"
" `__aenter__` exits. Consider replacing with `.start()`."
),
}
def __init__(self, *args: Any, **kwargs: Any):
super().__init__(*args, **kwargs)
# this is not entirely correct, it's trio.open_nursery.__aenter__()->trio.Nursery
# but VisitorTypeTracker currently does not work like that.
self.typed_calls["trio.open_nursery"] = "trio.Nursery"
self.typed_calls["anyio.create_task_group"] = "anyio.TaskGroup"
self.typed_calls["asyncio.TaskGroup"] = "asyncio.TaskGroup"
self.async_function = False
self.asynccontextmanager = False
self.aenter = False
def visit_AsyncFunctionDef(self, node: ast.AsyncFunctionDef):
self.save_state(node, "aenter")
self.aenter = node.name == "__aenter__" or has_decorator(
node, "asynccontextmanager"
)
def visit_Yield(self, node: ast.Yield):
self.aenter = False
def visit_Call(self, node: ast.Call) -> None:
def is_startable(n: ast.expr, *startable_list: str) -> bool:
if isinstance(n, ast.Name):
return n.id in startable_list
if isinstance(n, ast.Attribute):
return n.attr in startable_list
if isinstance(n, ast.Call):
return any(is_startable(nn, *startable_list) for nn in n.args)
return False
def is_nursery_call(node: ast.expr):
if not isinstance(node, ast.Attribute) or node.attr not in (
"start_soon",
"create_task",
):
return False
var = ast.unparse(node.value)
return ("trio" in self.library and var.endswith("nursery")) or (
self.variables.get(var, "")
in (
"trio.Nursery",
"anyio.TaskGroup",
"asyncio.TaskGroup",
)
)
if (
self.aenter
and is_nursery_call(node.func)
and len(node.args) > 0
and is_startable(
node.args[0],
*STARTABLE_CALLS,
*self.options.startable_in_context_manager,
)
):
self.error(node)
# Checks that all async functions with a "task_status" parameter have a match in
# --startable-in-context-manager. Will only match against the last part of the option
# name, so may miss cases where functions are named the same in different modules/classes
# and option names are specified including the module name.
@error_class
class Visitor114(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC114": (
"Startable function {} not in --startable-in-context-manager parameter "
"list, please add it so ASYNC113 can catch errors using it."
),
}
def visit_AsyncFunctionDef(self, node: ast.AsyncFunctionDef):
if any(
isinstance(n, ast.arg) and n.arg == "task_status"
for n in self.walk(*node.args.args, *node.args.kwonlyargs)
) and not any(
node.name == opt
for opt in (*self.options.startable_in_context_manager, *STARTABLE_CALLS)
):
self.error(node, node.name)
# Suggests replacing all `[trio|anyio].sleep(0)` with the more suggestive
# `trio.lowlevel.checkpoint()`
@error_class
class Visitor115(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC115": "Use `{0}.lowlevel.checkpoint()` instead of `{0}.sleep(0)`.",
}
def visit_Call(self, node: ast.Call):
if (
(m := get_matching_call(node, "sleep"))
and len(node.args) == 1
and isinstance(node.args[0], ast.Constant)
and node.args[0].value == 0
):
# m[2] is set to node.func.value.id
self.error(node, m[2])
@error_class
class Visitor116(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC116": (
"{0}.sleep() with >24 hour interval should usually be "
"`{0}.sleep_forever()`."
),
}
def visit_Call(self, node: ast.Call):
if (m := get_matching_call(node, "sleep")) and len(node.args) == 1:
arg = node.args[0]
if (
# `trio.sleep(math.inf)`
(isinstance(arg, ast.Attribute) and arg.attr == "inf")
# `trio.sleep(inf)`
or (isinstance(arg, ast.Name) and arg.id == "inf")
# `trio.sleep(float("inf"))`
or (
isinstance(arg, ast.Call)
and isinstance(arg.func, ast.Name)
and arg.func.id == "float"
and len(arg.args)
and isinstance(arg.args[0], ast.Constant)
and arg.args[0].value == "inf"
)
# `trio.sleep(1e999)` (constant value inf)
# `trio.sleep(86401)`
# `trio.sleep(86400.1)`
or (
isinstance(arg, ast.Constant)
and isinstance(arg.value, (int, float))
and arg.value > 86400
)
):
self.error(node, m[2])
@error_class
class Visitor119(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC119": "Yield in contextmanager in async generator might not trigger"
" cleanup. Use `@asynccontextmanager` or refactor."
}
def __init__(self, *args: Any, **kwargs: Any):
super().__init__(*args, **kwargs)
self.unsafe_function: bool = False
self.contextmanager: bool = False
def visit_AsyncFunctionDef(
self, node: ast.AsyncFunctionDef | ast.FunctionDef | ast.Lambda
):
self.save_state(node, "unsafe_function", "contextmanager")
self.contextmanager = False
if isinstance(node, ast.AsyncFunctionDef) and not has_decorator(
node, "asynccontextmanager"
):
self.unsafe_function = True
else:
self.unsafe_function = False
def visit_With(self, node: ast.With | ast.AsyncWith):
self.save_state(node, "contextmanager")
self.contextmanager = True
def visit_Yield(self, node: ast.Yield):
if self.unsafe_function and self.contextmanager:
self.error(node)
visit_AsyncWith = visit_With
visit_FunctionDef = visit_AsyncFunctionDef
# it's not possible to yield or open context managers in lambda's, so this
# one isn't strictly needed afaik.
visit_Lambda = visit_AsyncFunctionDef
@error_class_cst
class Visitor300(Flake8AsyncVisitor_cst):
error_codes: Mapping[str, str] = {
"ASYNC300": "asyncio.create_task() called without saving the result"
}
def __init__(self, *args: Any, **kwargs: Any):
super().__init__(*args, **kwargs)
self.safe_to_create_task: bool = False
def visit_Assign(self, node: cst.CSTNode):
self.save_state(node, "safe_to_create_task")
self.safe_to_create_task = True
def visit_CompIf(self, node: cst.CSTNode):
self.save_state(node, "safe_to_create_task")
self.safe_to_create_task = False
def visit_Call(self, node: cst.Call):
if (
isinstance(node.func, (cst.Name, cst.Attribute))
and identifier_to_string(node.func) == "asyncio.create_task"
and not self.safe_to_create_task
):
self.error(node)
self.visit_Assign(node)
visit_NamedExpr = visit_Assign
visit_AugAssign = visit_Assign
visit_IfExp_test = visit_CompIf
# because this is a Flake8AsyncVisitor_cst, we need to manually call restore_state
def leave_Assign(
self, original_node: cst.CSTNode, updated_node: cst.CSTNode
) -> Any:
self.restore_state(original_node)
return updated_node
leave_Call = leave_Assign
leave_CompIf = leave_Assign
leave_NamedExpr = leave_Assign
leave_AugAssign = leave_Assign
def leave_IfExp_test(self, node: cst.IfExp):
self.restore_state(node)
@error_class
@disabled_by_default
class Visitor900(Flake8AsyncVisitor):
error_codes: Mapping[str, str] = {
"ASYNC900": "Async generator not allowed, unless transformed "
"by a known decorator (one of: {})."
}
def __init__(self, *args: Any, **kwargs: Any):
super().__init__(*args, **kwargs)
self.unsafe_function: ast.AsyncFunctionDef | None = None
self.transform_decorators = (
"asynccontextmanager",
"fixture",
*self.options.transform_async_generator_decorators,
)
def visit_AsyncFunctionDef(
self, node: ast.AsyncFunctionDef | ast.FunctionDef | ast.Lambda
):
self.save_state(node, "unsafe_function")
if isinstance(node, ast.AsyncFunctionDef) and not has_decorator(
node, *self.transform_decorators
):
self.unsafe_function = node
else:
self.unsafe_function = None
def visit_Yield(self, node: ast.Yield):
if self.unsafe_function is not None:
self.error(self.unsafe_function, ", ".join(self.transform_decorators))
self.unsafe_function = None
visit_FunctionDef = visit_AsyncFunctionDef
visit_Lambda = visit_AsyncFunctionDef