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

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# Return in Generator
# Detects 'return' with a value in generator functions (with 'yield')
id: return-in-generator
name: Return with Value in Generator
severity: error
category: reliability
defect_class: correctness
inline_tier: blocking
language: python

message: "'return' with a value should not be used in a generator function"

description: |
  In Python 3.3+, using 'return <value>' in a generator sets the
  StopIteration.value, which is rarely intended. Use 'return' without
  a value, or yield the value instead.

  ✅ FIX: Remove the return value or yield it

  ```python
  def my_generator():
      yield 1
      yield 2
      return  # OK - no value
  ```

query: |
  (function_definition
    body: (block
      (return_statement
        (_) @RETURN_VAL) @RETURN)) @FUNCTION

metavars:
  - FUNCTION
  - RETURN
  - RETURN_VAL

post_filter: is_generator_with_valued_return

tags:
  - reliability
  - python-specific
  - generator

examples:
  bad: |
    def my_gen():
        yield 1
        return 42  # BAD - StopIteration.value is rarely intended

  good: |
    def my_gen():
        yield 1
        yield 42  # GOOD - yield instead
        return  # GOOD - return without value

has_fix: true
fix_action: remove_return_value