pi-lens/rules/tree-sitter-queries/python/return-in-init.yml

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# Return in __init__
# Detects __init__ methods that explicitly return a value (should return None)
id: return-in-init
name: Return Value in __init__
severity: error
category: reliability
defect_class: correctness
inline_tier: blocking
language: python

message: "__init__ should not return a value — it must always return None"

description: |
  The __init__ method in Python must not return any value other than None.
  Returning a value from __init__ will raise a TypeError at runtime.

  ✅ FIX: Remove the return statement or return None implicitly

  ```python
  class MyClass:
      def __init__(self, value):
          self.value = value
          # No return statement needed
  ```

query: |
  (function_definition
    name: (identifier) @NAME (#eq? @NAME "__init__")
    body: (block
      (return_statement
        (_) @RETURN_VAL) @RETURN))

metavars:
  - NAME
  - RETURN
  - RETURN_VAL

tags:
  - reliability
  - python-specific
  - runtime-error

examples:
  bad: |
    class MyClass:
        def __init__(self, value):
            self.value = value
            return self  # BAD - TypeError at runtime!

  good: |
    class MyClass:
        def __init__(self, value):
            self.value = value
            # Implicit return None is correct

has_fix: true
fix_action: remove_return_value