image-match/python/py/Lib/site-packages/pylint/checkers/lambda_expressions.py

# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/pylint-dev/pylint/blob/main/LICENSE
# Copyright (c) https://github.com/pylint-dev/pylint/blob/main/CONTRIBUTORS.txt

from __future__ import annotations

from itertools import zip_longest
from typing import TYPE_CHECKING

from astroid import nodes

from pylint.checkers import BaseChecker
from pylint.interfaces import HIGH

if TYPE_CHECKING:
    from pylint.lint import PyLinter


class LambdaExpressionChecker(BaseChecker):
    """Check for unnecessary usage of lambda expressions."""

    name = "lambda-expressions"
    msgs = {
        "C3001": (
            "Lambda expression assigned to a variable. "
            'Define a function using the "def" keyword instead.',
            "unnecessary-lambda-assignment",
            "Used when a lambda expression is assigned to variable "
            'rather than defining a standard function with the "def" keyword.',
        ),
        "C3002": (
            "Lambda expression called directly. Execute the expression inline instead.",
            "unnecessary-direct-lambda-call",
            "Used when a lambda expression is directly called "
            "rather than executing its contents inline.",
        ),
    }
    options = ()

    def visit_assign(self, node: nodes.Assign) -> None:
        """Check if lambda expression is assigned to a variable."""
        match node:
            case nodes.Assign(
                targets=[nodes.AssignName(), *_], value=nodes.Lambda() as value
            ):
                self.add_message(
                    "unnecessary-lambda-assignment",
                    node=value,
                    confidence=HIGH,
                )
            case nodes.Assign(
                targets=[nodes.Tuple() as target, *_],
                value=nodes.Tuple() | nodes.List() as value,
            ):
                # Iterate over tuple unpacking assignment elements and
                # see if any lambdas are assigned to a variable.
                # N.B. We may encounter W0632 (unbalanced-tuple-unpacking)
                # and still need to flag the lambdas that are being assigned.
                for lhs_elem, rhs_elem in zip_longest(target.elts, value.elts):
                    if lhs_elem is None or rhs_elem is None:
                        # unbalanced tuple unpacking. stop checking.
                        break
                    if isinstance(lhs_elem, nodes.AssignName) and isinstance(
                        rhs_elem, nodes.Lambda
                    ):
                        self.add_message(
                            "unnecessary-lambda-assignment",
                            node=rhs_elem,
                            confidence=HIGH,
                        )

    def visit_namedexpr(self, node: nodes.NamedExpr) -> None:
        match node:
            case nodes.NamedExpr(
                target=nodes.AssignName(), value=nodes.Lambda() as value
            ):
                self.add_message(
                    "unnecessary-lambda-assignment",
                    node=value,
                    confidence=HIGH,
                )

    def visit_call(self, node: nodes.Call) -> None:
        """Check if lambda expression is called directly."""
        if isinstance(node.func, nodes.Lambda):
            self.add_message(
                "unnecessary-direct-lambda-call",
                node=node,
                confidence=HIGH,
            )


def register(linter: PyLinter) -> None:
    linter.register_checker(LambdaExpressionChecker(linter))