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from dataclasses import dataclass
from mypy.nodes import CallExpr, IndexExpr, IntExpr, MemberExpr, NameExpr, RefExpr, SliceExpr
from refurb.checks.common import stringify
from refurb.error import Error
@dataclass
class ErrorInfo(Error):
"""
Depending on how you are using the `secrets` module, there might be more
expressive ways of writing what it is you're trying to write.
Bad:
```
random_hex = token_bytes().hex()
random_url = token_urlsafe()[:16]
```
Good:
```
random_hex = token_hex()
random_url = token_urlsafe(16)
```
"""
name = "simplify-token-function"
code = 174
categories = ("readability", "secrets")
def check(node: CallExpr | IndexExpr, errors: list[Error]) -> None:
match node:
# Detects `token_bytes().hex()`
case CallExpr(
callee=MemberExpr(
expr=CallExpr(
callee=RefExpr(fullname="secrets.token_bytes") as ref,
args=token_args,
),
name="hex",
),
args=[],
):
match token_args:
case [IntExpr(value=value)]:
arg = str(value)
case [NameExpr(fullname="builtins.None")]:
arg = "None"
case []:
arg = ""
case _:
return
new_arg = "" if arg == "None" else arg
prefix = "secrets." if isinstance(ref, MemberExpr) else ""
old = f"{prefix}token_bytes({arg}).hex()"
new = f"{prefix}token_hex({new_arg})"
msg = f"Replace `{old}` with `{new}`"
errors.append(ErrorInfo.from_node(node, msg))
# Detects `token_xyz()[:x]`
case IndexExpr(
base=CallExpr(
callee=RefExpr(
fullname=fullname,
name=name, # type: ignore[misc]
) as ref,
args=[] | [NameExpr(fullname="builtins.None")] as args,
),
index=SliceExpr(
begin_index=None,
end_index=IntExpr(value=size),
stride=None,
),
) if fullname in {"secrets.token_hex", "secrets.token_bytes"}:
arg = "None" if args else ""
func_name = stringify(ref)
old = f"{func_name}({arg})[:{size}]"
# size must be multiple of 2 for hex functions since each hex digit
# takes up 2 bytes.
if name == "token_hex":
if size % 2 == 1:
return
size //= 2
new = f"{func_name}({size})"
msg = f"Replace `{old}` with `{new}`"
errors.append(ErrorInfo.from_node(node, msg))
|
