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Transform ID: class_to_dataclass Language: Python

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What it does

Detects classes whose __init__ method only does self.<name> = <name> assignments and rewrites them as @dataclass. Each former init parameter becomes a typed field (Any when the original parameter has no annotation).

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Detector pattern

The detector at src/analyze/detectors/python/class-init-only.ts walks ClassDef nodes, accepts only those with a single __init__ method, and verifies every body statement is an Assign(targets=[Attribute(self, name)], value=Name(name)) shape.

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Preconditions

  1. The class has exactly one method, and it is __init__.
  2. The __init__ body is purely self.<name> = <name> lines (no defaults, no transformations like self.x = x * 2).
  3. The class has no __slots__ declaration.
  4. The class does not inherit from a parent with a custom __init__.
  5. Init parameter names match the assignment target names (no self.public = _private redirection).

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Before / after

class User:
    def __init__(self, id, name, email):
        self.id = id
        self.name = name
        self.email = email


class Address:
    def __init__(self, street, city, zip):
        self.street = street
        self.city = city
        self.zip = zip

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Edge cases handled

  • Adds from dataclasses import dataclass and from typing import Any if missing.
  • Preserves class docstrings and decorators that precede the class.
  • Multiple convertible classes per file are all converted in one pass.

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Edge cases NOT handled (skip via precondition)

  • Class has any method besides __init__ (the transform refuses to promote — a dataclass with custom methods is fine in principle, but inferring eq/hash/repr interactions safely is out of scope for v0.2).
  • Init body contains expressions (self.id = id * 2, self.full_name = first + " " + last).
  • Init has default arguments (def __init__(self, x=0)) — supported by dataclass via field(default=…) but not auto-inferred here.
  • Class uses __slots__.