wehub-resource-sync
65 lines
2.0 KiB
Python
65 lines
2.0 KiB
Python
import ast
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from clint.rules.base import Rule
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class AssignBeforeAppend(Rule):
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def _message(self) -> str:
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return (
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"Avoid unnecessary assignment before appending to a list. "
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"Use a list comprehension instead."
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)
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@staticmethod
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def check(node: ast.For, prev_stmt: ast.stmt | None) -> bool:
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"""
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Returns True if the for loop contains exactly two statements:
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an assignment followed by appending that variable to a list, AND
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the loop is immediately preceded by an empty list initialization.
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Examples that should be flagged:
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---
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items = []
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for x in data:
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item = transform(x)
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items.append(item)
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---
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"""
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# Match: for loop with exactly 2 statements in body
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match node:
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case ast.For(body=[stmt1, stmt2]):
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pass
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case _:
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return False
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# Match stmt1: simple assignment (item = x)
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match stmt1:
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case ast.Assign(targets=[ast.Name(id=assigned_var)]):
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pass
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case _:
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return False
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# Match stmt2: list.append(item)
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match stmt2:
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case ast.Expr(
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value=ast.Call(
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func=ast.Attribute(value=ast.Name(id=list_name), attr="append"),
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args=[ast.Name(id=appended_var)],
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)
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):
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# Check if the appended variable is the same as the assigned variable
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if appended_var != assigned_var:
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return False
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case _:
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return False
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# Only flag if prev_stmt is empty list initialization for the same list
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match prev_stmt:
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case ast.Assign(
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targets=[ast.Name(id=prev_list_name)],
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value=ast.List(elts=[]),
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) if prev_list_name == list_name:
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return True
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case _:
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return False
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